The hardening strain model with small strain (HSS) can reflect the high nonlinearity of soil modulus at small strain range, which has been widely applied in deformation calculations during pit excavations under complex geological conditions. The appropriate values of model parameters have a significant impact on the computational results. However, the current recommended parameter values have a large range of fluctuations, which brings inconvenience to engineering applications. Therefore, further research is needed on the parameter values of the model. This study analyzes the data characteristics of existing HSS model parameters and introduces the artificial neural network method (ANN). The empirical relationships between the modulus parameters of the HSS model for Shanghai soils and factors such as the initial pore ratio (e) and oedometer modulus (E_s1-2) are established. This allows for the rapid determination of HSS model modulus parameters based on survey reports. Compared with the recommended values, the proposed method for determining the HSS model modulus parameters is closer to the measured value. The study results can provide references for projects in Shanghai.

To address the challenges faced by transmission line tower foundation projects in complex mountainous environments, a root pile foundation composed of a short pile and three inclined anchor rods evenly distributed around the pile is proposed, aiming to enhance the uplift resistance of the pile foundation. Through field prototype testing, the vertical displacement of the pile top, anchor rod axial force, failure modes, and load distribution coefficient of the root pile foundation under uplift load were investigated. The results show that: The uplift load-displacement curve of the root pile foundation can be divided into three stages, including initial elastic straight line stage, elastoplastic curve transition stage, and the linear failure stage. In the early loading stage, the load-bearing capacity of the anchor rods is not significantly demonstrated, but as the load increases, the axial force of the anchor rods continues to grow. The ultimate uplift bearing capacity of the root pile foundation increased by 29.41% compared to that of the short pile foundation, indicating that the inclined anchor rods significantly improved the load-bearing capacity of the root pile foundation. Additionally, radial and circumferential cracks formed around the root pile foundation, with the main cracks concentrated in the area where the inclined anchor rods were arranged, presenting a radial distribution. This is because the anchor rods compress the soil and rock mass upwards, causing tensile failure in the upper soil and rock mass, and ultimately leading to the failure of the anchor rod structure due to tensile damage. Analyzing the bearing mechanism of the root pile foundation, the load distribution coefficient between short piles and inclined anchor rods can be used to characterize the bearing characteristics of the root pile foundation, and both components working together to bear the load. During the test, the load distribution coefficient of the inclined anchor rods gradually increased from a low level in the early loading stage to 48%, effectively dispersing and transferring the load. The research findings can provide a theoretical basis for the design and optimization of transmission line tower foundations in complex mountainous environments.

The utilization scale of underground space in China will continue to grow for a long period of time in the future, which can provide sufficient and stable space and facility support for a variety of emission reduction and sink enhancement technologies, and has great significance to the achievement of the goal of carbon peaking and carbon neutrality. In order to reveal the research hotspots and trend of China's underground space in response to the goal of carbon peaking and carbon neutrality, 944 academic papers published in the CNKI database before Jan., 2024 were used as data samples, and a visual analysis was conducted based on the VOSviewer software to analyze the number of annual publications, the distribution of journals, keywords, and institutions of publications in this field. The results of the study show that the research literature on the response of China's underground space to the goal of carbon peaking and carbon neutrality has shown fluctuating growth, with a significant increase in the number of literature in the past two years; the research content mainly focuses on the low-carbon effect of the subway, carbon utilization and storage in underground, and underground energy storage, etc. The research trend of China's underground space in response to the goal of carbon peaking and carbon neutrality is analyzed from four aspects, namely, spatial compactness, energy diversity, functional integration, and construction phasing.

For large-section tunnels crossing fault fracture zones, indoor experiments were conducted to study the mechanical and permeability characteristics of the rock specimen. Based on the correlation between rock integrity index and physical and mechanical indicators, the parameters of surrounding rock under different degrees of fragmentation were quantified. Considering the permeability of surrounding rock changes with confining pressure, a three-dimensional numerical model was established to analyze the impact of the engineering characteristics of fractured zone surrounding rock on the tunnel deformation. Through on-site monitoring, the deformation of the tunnel and the stress changes of the support structure are mastered. The results show that: (1) The mechanical properties of the rock specimen in the fractured zone are greatly affected by the water-rock interaction, and the peak stress of the rock specimen in the saturated state is significantly reduced compared to the dry state. (2) The permeability of the rock specimen in the fractured zone decreases in a logarithmic relationship with the increase of confining pressure. When the confining pressure exceeds the crack closure stress, the penetration water pressure of the rock sample approaches. (3) As the integrity index K_v of the rock mass in the fault fracture zone decreases, the maximum settlement of the tunnel arch increases in a logarithmic relationship, and the adverse effect of seepage on tunnel deformation increases. (4) By taking reasonable strengthening support measures and parameters, the tunnel can safely pass through the mileage section of the fault fracture zone, which can be used as a reference for engineering applications.

In the context of urban renewal, how to meet the public's demand for spatial quality in existing underground commercial streets has become an urgent problem to be solved. Corner space, as an important node in the pedestrian system of underground commercial streets, is a key area that affects spatial vitality, walking direction, pedestrian physiology, and psychology. Based on a pedestrian-friendly perspective, the impact of distance, constituent elements, and angles between different underground corners on pedestrian behavior is explored, and an adaptive corner space optimization strategy for (single building) underground commercial streets is proposed using spatial operation methods. The study aims to provide practical application value for optimizing the design of corner spaces in underground commercial streets. The results indicate that: Using obtuse corner angles, appropriate corner spacing, and increasing the boundary area at the corner can effectively enhance the overall vitality of the street and the attractiveness of shops.

In order to investigate the mechanical state of pre-stressed anchors for tunnel support under water-rich ground conditions, an elastoplastic analysis of the tunnel surrounding rock was carried out based on the three-dimensional Hoek-Brown failure criterion, considering the effects of hydraulic coupling and strain softening of the surrounding rock, and considering the pre-stressed anchors as a passive anchor model with anchor pads and non-zero strain at both ends. The numerical calculation method of shear stress distribution and end prestress of prestressing anchor was established by using bond-slip theory. Through the comparison and analysis of the calculation results of relevant engineering cases, the rationality of the calculation method in this study is verified. At the same time, parametric analysis is carried out on the change law of surrounding rock stress and displacement under the influence of different factors by relying on the actual project. The results show that: The maximum values of anchor shaft force, tunnel surface force, and anchor neutral point are well-fitted with the monitoring values of the selected engineering cases. When the anchor shear stress reaches the peak stress of the tunnel wall, the decoupling phenomenon occurs between the anchor and the surrounding rock near the tunnel wall. The actual project reflects that the method of this study can effectively solve the design calculation problem of pre-stressed anchors in the deep tunnel, and the pre-stressed anchors can effectively reduce the surrounding rock deformation after installation. Compared with the passive anchor, its support effect is better. The study results can theoretical guidance for the design of the deep tunnel support under similar engineering geological conditions.

Urban land scarcity and increasing student numbers have limited the development of old university campuses. This study proposes a new concept of integrating above-ground and underground space for the study of the renovation design of old university campuses and applies this new concept to the Xueyuan Road Campus of China University of Mining and Technology (Beijing). The study was carried out with a focus on four aspects: functional zoning integration, traffic optimization, emergency evacuation of underground space, and space quality improvement. Adjustment of the functionality and zoning of the campus by analyzing the demolition of some of the existing old buildings, taking into account the surrounding environment and the above and below-ground conditions of the campus after the demolition, to separate pedestrian and motor vehicle traffic on campus. In this design, the large-scale gymnasium is underground beneath the playground where the upper space cannot be opened. An innovative "functional area-secondary safe area-safe area (sunken space)" evacuation system is proposed, and its feasibility was verified using the simulation software. Sunken corridors, sunken courtyards, and skylights were used to solve the problems of lighting in underground spaces. The methodology described in this paper effectively increased the area of various buildings on the campus and significantly improved the quality of the campus space. Our results provide a plan for the renovation of the Xueyuan Road Campus of China University of Mining and Technology (Beijing), and provide an effective method for the renovation of old university campuses.

The space around the proposed excavation in complex environments becomes increasingly limited, the semi-infinite space assumed by the classical earth pressure theory is inconsistent with actual engineering, resulting in a lack of reasonable calculation methods for active earth pressure in excavations with limited soil. Taking the flexible retaining piles and sandy soil of limited soil excavations as the research objects, using the single-row pile cantilever retaining mode and the bottom ends of the retaining piles fixed, four excavations model tests under different soil widths were carried out. To explore the distribution characteristics of active earth pressure and horizontal displacement of retaining piles along the retaining piles. The results show that the horizontal displacement of the retaining structure on each soil width side approximates a triangular displacement pattern, and the earth pressure gradually approximates a D-shaped distribution as the excavation depth increases, with the maximum value appearing at approximately 0.8H depth. The force analysis of the soil differential unit was performed through the limit equilibrium method, and the active earth pressure distribution of the finite soil under the limit state was deduced. Combined with the friction angle development model that considers the influence of displacement, the non-limit active earth pressure distribution and resultant force of the finite soil were deduced. and the height of the point of action. The effectiveness of the calculation method in this paper is verified by comparing the earth pressure test values with the theoretical values in this paper. Through parameter analysis, it was found that the earth pressure is positively related to the aspect ratio and negatively related to the internal friction angle. The critical aspect ratio n_cr = 0.5 to distinguish between finite soil and semi-infinite soil.

In order to study the influence of different water content and salt content on the water-salt migration mechanism of Ili salinized loess. The water-salt migration test of saline loess under the action of the freeze-thaw cycle was carried out, and the temperature, moisture, and salt fields and their cohesion change rules were analyzed. The study shows that under the action of freezing and thawing, the temperature field, moisture field and salt field of saline loess show cyclic changes. With the increase of the number of freezing and thawing cycles, the water content of the soil column as a whole is increased, showing a pattern of high water content at the two ends and low water content in the middle. The change of salts in the soil layer under freezing and thawing is consistent with the overall change of moisture, and the salts in each soil layer show a homogeneous distribution before the unfreezing and thawing. Under the effect of temperature potential, the water carries the salts to migrate upward, resulting in higher salinity in the middle and upper part of the soil column. The increase of water content and salinity has a promoting effect on the migration of water and salts. In addition, the increase in water content will have a lubricating effect between the soil particles, resulting in the cohesion of the sample with low water content being greater than that of the sample with high water content. With the increase of salt content, the agglomerates formed by the salt crystals wrapped around the soil particles play the role of skeleton, which makes the cohesion of the specimen with high salt content larger than that of the specimen with low salt content, the value of internal friction angle of salinized loess after freeze-thawing shows a wave distribution.

The construction of utility tunnel plays a significant role in improving the resilience of urban lifelines and intensively utilizing urban three-dimensional space. It is an important infrastructure that serves the city's high-quality development. Based on the practical needs of urban utility tunnel planning and construction, the analytic hierarchy process and expert consultation method were used to clarify the assignment rules and weights of 15 key influencing factors, and build a suitability evaluation system for urban utility tunnel planning and construction. With the help of the spatial analysis and statistical functions of GIS, the suitability of the utility tunnel in the study area was evaluated more scientifically and objectively. The construction scale was optimized using the construction rate of the utility tunnel and the density of the urban utility tunnel construction indicators, reaching a balance of the coverage of the utility tunnel construction with the expenditure on infrastructure construction. This study provides support for regional utility tunnel planning schemes.

The Burgers mechanical creep model is extensively used in frozen soil engineering for its concise mathematical formulation. The accuracy of this model's calculations significantly depends on the precision with which its parameters are determined. The current practice of using the “trial and error” method to ascertain these parameters often lacks clear physical rationale, thus undermining the model's reliability. This paper presents a study on frozen silty clay under various temperatures and axial pressures, employing uniaxial creep tests to refine the parameter determination process. By integrating the Burgers model with empirical data, the physical significance of its parameters is delineated: the Maxwell elastic shear modulus G_M is derived from the instantaneous strain upon loading, the Maxwell viscosity coefficient H_M is based on the slope of the linear section of the creep curve, the Kelvin elastic shear modulus G_K is ascertained from the intersection of the linear section's extension with the strain axis, and the Kelvin viscosity coefficient H_K is calculated from a specific point on the nonlinear deceleration phase of the creep curve. This approach circumvents the limitations of the traditional trial-and-error method, offering a theoretical foundation for parameter determination that is more scientific, intuitive, and efficient. Comparative analysis of experimental and computational outcomes confirms the Burgers model's efficacy in accurately depicting the attenuation and stable progression phases of frozen soil creep. This validation suggests that the parameter determination method proposed in this study is effective.

Gravel piles are widely used in engineering, and their bearing capacity is an important indicator for evaluating the performance of gravel pile projects. Based on the cavity expansion theory, the calculation formula of bearing capacity of single gravel pile is derived by introducing the extended Lade-Duncan failure criterion, and considering the superimposed effect of stress expansion, the calculation formula of bearing capacity of single gravel pile under square layout scheme is derived. The laboratory scale model test shows that the maximum swelling depth of stone column is about twice the depth of pile diameter, which provides a basis for theoretical calculation. Finally, the proposed calculation method is compared and verified by field tests and existing research results. The results show that: The calculation results of the existing bearing capacity calculation formula of the crushed stone column are conservative, and the bearing capacity obtained by introducing the calculation formula of the extended Lade-Duncan failure criterion is closer to the measured value. This study can provide reference for related engineering and research.

To reduce the vibration intensity of wedge-shape excavation blasting in tunnel, the precisely controlled delay time technology of tunnel V-cut blasting was proposed based on the Mohr-Coulomb strength criterion, the maximum tensile stress, and Anderson superposition theory. Firstly, the mechanism of segmental blasting of V-cut is revealed through theoretical analysis. Secondly, the function of blasting vibration waves was obtained by fitting the Gauss function. Finally, the precise delay time of reducing blasting vibration was obtained by superimposing different delay times with Matlab. The results show that: The stepped V-cut blasting improves the free surface conditions of blasting, and weakens the vibration propagation energy by reducing the amount of blasting charge in a single stage. Based on the Qi Jiazhuang tunnel of National Highway 109, the vibration strength of V-cut blasting was reduced by about 60% when the delay time was 13 ms. The engineering practice showed that the relative error between the theory and the field monitoring data was 13.9%, which verified the validity of the technology.

Shield tunneling method is widely used in subway tunnel construction because of its advantages such as not affecting ground traffic, high mechanization degree and short construction period. However, the problems of cracking and damage caused by uneven rising of segments are often encountered in the construction process of shield method, which affects the normal use of tunnel. However, the research on the mechanism and theoretical calculation of shield tunnel segment floating is relatively rare. In this paper, the floating mechanism of segments in the initial floating stage of shield tunnel is analyzed deeply, and the corresponding theoretical calculation formulas of upward buoyancy/anti-buoyancy and buoyancy are proposed. The theoretical calculation results are compared and analyzed with engineering examples. The results show that: The initial floating of the segment can be divided into two stages: rapid rising and slow rising, in which the rising amount of the rapid rising stage accounts for about 80%~90% of the total rising amount. The theoretical calculation value of the total floating amount is greater than the monitoring value, but the calculation error of the floating amount per ring is relatively stable, the theoretical calculation formula presented in this paper can provide reference for the calculation of the floating amount of the actual segment.

Nowadays, when the country vigorously promotes "high-quality development", the requirements of laboratory environment in various disciplines in universities are gradually improving. In the context of "reducing the development" of Beijing's overall planning policy, the utilization of campus underground space has become one of the indispensable means for the development of universities in Beijing in recent years. Meanwhile, the strong anti-interference of the underground laboratory also shows important advantages. By investigating and analyzing the existing literature of cases of campus underground experimental space at home and abroad, several design principles of underground experimental buildings are summarized. On this basis, combined with the current situation of the location and the function of the peripheral existing buildings, planning and design on the surrounding underground space of the observatory, located in the western part of Tsinghua University campus has been done. Different schemes for the ground entrance form, plane function and streamline organization logic have also been compared, which is hoped to provide reference for the future development of the campus underground experimental space in Tsinghua University.

The triaxial test based on photogrammetry can realize the real-time measurement of the local deformation of the specimen, but the refraction of light leads to the error in the measurement of specimen deformation. The introduction of the refraction correction factor (κ) can not only solve this problem, but also improve the test efficiency. In order to investigate the trend of the refraction correction coefficient in the axial and radial deformation measurements of different specimens, and to analyze the difference between the stress-strain curves measured by applying the refraction correction coefficient and those of the conventional triaxial tests, the photogrammetric-based consolidation and drainage triaxial tests were carried out on red clay and sandy clay, respectively. The results show that: (1) In the axial deformation measurement, the refraction correction coefficients of the different local regions of the red clay and the sandy clay converged to 1, and the refraction amplification effect on the axial deformation measurement of the specimen is negligible; (2) In the radial deformation measurement, the refraction correction coefficients of the red clay and sandy soil are 0.812 and 0.757, respectively. The refraction amplification effect has a greater impact on the radial deformation measurement of the specimen, and the refraction correction coefficients of the different specimens correspond to different refraction correction coefficients; (3) The change trends of the stress-strain curves measured by conventional triaxial and the application of refraction correction coefficient. The stress-strain curves measured by conventional triaxial and by applying the refraction correction coefficient have the same trend, and the bias stress measured by applying the refraction correction coefficient photogrammetry is relatively small in the middle and late stages of the test.

At present, many integration construction problems such as the disconnection of integrated development of urban rail stations and surrounding areas, insufficient integration of stations and cities, insufficient accessibility, and low comprehensive benefits are becoming more and more prominent, and at the same time, the mechanism for supervising and implementing the assessment of urban rail stations is not yet perfect. Based on the framework of urban rail station assessment system, this paper established an integrated assessment index system for urban rail stations from eight dimensions, including land function, traffic organisation, spatial environment, commercial vitality, economic benefits, safety resilience, underground space and implementation effectiveness, and took 32 rail stations in Beijing as the objects of study, and carried out the assessment and classification of the rail stations in different radial scales by using entropy Weight-TOPSIS method. Evaluation and classification of different radiation scales of rail stations were carried out by using entropy Weight-TOPSIS method. The results show that there are spatial differences in the influencing factors of rail station integration construction in different radiation scales of rail stations, and the assessment results are divided into four categories by using K-means clustering, and classification optimisation suggestions are put forward.

In order to study the crack-resistance performance of fiber-reinforced composite (FRP) reinforced tunnel cracked lining, based on the peridynamics theory, a peridynamics simulation method for FRP reinforced concrete structures is established by introducing the interface weakening criteria. Four-point bending tests of FRP reinforced concrete beams are conducted to verify the simulation method. The problem of FRP reinforced tunnel cracked lining is modeled and analyzed to explore the influence of FRP reinforcement width and layers on the reinforcement performance of various cracked linings. The results indicate that: Interfacial debonding is the main failure mode of FRP reinforced cracked lining. The width and number of layers of FRP reinforcement are positively correlated with the reinforcement performance. Nevertheless, when the reinforcement width exceeds 2/3 of the arch bottom and the number of layers exceeds 2, the structural reinforcement performance does not significantly improve. In addition, the distribution and depth of cracks have a significant impact on the reinforcement performance of FRP, and the reinforcement effect of mid-span cracks is significantly better than that of eccentric cracks. Moreover, when the height ratio of mid span cracks is 1/5, the global damage index of FRP reinforcement lining decreases by 40.3%, significantly improving the crack resistance performance of the structure.

In order to further investigate the deformation and strength characteristics of transversely isotropic unsaturated remolded loess under complex stress paths, three sets of 39 consolidation shear tests were conducted on transversely isotropic unsaturated soil using different experimental instruments (unsaturated true triaxial apparatus and unsaturated triaxial apparatus). The results show that: In true triaxial shear tests, the stress-strain relationship curve of the specimen exhibits strain hardening characteristics and has a hyperbolic shape, and the stress also increases with the increase of suction force.As the shearing process continues, the moisture content of the true triaxial specimen decreases continuously. Under the same b value and net confining pressure conditions, the greater the suction force, the greater the slope of the moisture content axial strain relationship curve. The true triaxial specimen, K₀CD test specimen, and K₀′CD test specimen consistently exhibit a state of shear shrinkage during the shear test. The magnitude of the failure stress of the test specimens under three different initial conditions is highest for the true triaxial test specimen, followed by the K₀CD test specimen, and lowest for the K₀′CD test specimen. The initial tangent modulus of the K₀CD test specimen is the highest, followed by the K₀′CD test specimen, and the true triaxial test specimen is the smallest. The research results are of great significance for promoting the study of mechanical properties of transversely isotropic unsaturated loess, improving relevant theories and criteria, and guiding engineering practice.

The traditional algorithm is unable to accurately calculate the ultimate bearing capacity of heavy soil foundation, whereas numerical limit analysis methods can do so precisely. It can be seen that numerical limit analysis can solve geotechnical engineering problems more complex than traditional analytical methods. The incremental load method is used, which applies the principle of failure of engineering materials from quantitative to qualitative changes in stress. As the foundation load gradually increases, the stress on the soil foundation transitions from elastic to plastic, and finally reaches the ultimate failure state, obtaining the corresponding ultimate load value. The ultimate bearing capacity of the foundation under strip foundation load was obtained by combining engineering examples, and compared with the traditional empirical results of Terzaghi, Vesic, and Chen. The results show that the numerical limit analysis method can save 40%, 20%, and similar foundation engineering quantities compared to Terzaghi, Vesic, and Chen empirical methods, respectively. At present, both Terzaghi formula and Vesic formula are applied in practical projects, while Chen formula has not been applied yet.

Rock anchorage is a new type anchorage structure of suspension bridge with complex stress mechanisms. In order to study the deformation characteristics and bearing capacity of the suspension bridge rock anchorage, the 1∶10 scaled model tests on site are carried out based on the Xihoumen Rail-cum-Road Bridge rock anchorage project. By sequentially conducting tests on 1.2P prestressing condition loading, 1P design load condition loading, and overload condition loading, the deformation distribution law of the rock anchorage under various working conditions are analyzed and the bearing characteristics of the rock anchorage are studied. According to the research, the deformation of rock anchorage mainly occurs in the two rock anchorage bodies and the rock mass area between them under various working conditions. And the deformation distribution curve is characterized by a bimodal shape centered on the rock mass between the anchorages.Under the design load condition, the maximum deformation of the actual bridge rock anchorage is 4.17 mm. Moreover, and the safety stability coefficient of the actual bridge rock anchorage is 11. Both deformation and safety stability coefficient of the suspension bridge anchorage are meet the requirements of the specifications. The research results may provide the experimental basis for the safety evaluation of the rock anchorage of the Xihoumen Rail-cum-Road Bridge, and also provide the technical reference for the research and application of rock anchorage related issues.

The development of underground transportation based on TOD mode drives the process of underground development of surrounding commercial space, and the connectivity between underground transportation and commercial space has become a link that cannot be ignored. Based on the place theory, this study highly summarizes the spatial composition of the two connected Spaces of Shanghai People's Square Station and Xujiahui Station. Considering the spatial structure and place spirit, field investigation and questionnaire distribution are conducted. Moreover, exploratory factor analysis and SPSS algorithm software are used to find out the strongly related reasons affecting the connectivity quality. By quantifying the subjective factors of pedestrians, five influencing factors are summarized, namely, central place and direction, regional division and shaping, spatial theme culture, spatial interaction, public safety and management, and corresponding optimization method are proposed to provide some reference for the design of underground connected space.

Air-raid shelter is an important component of the underground space in Chongqing city. During the Anti-Japanese War period, they served as shelters for military and civilian production and life, enhancing the overall protection capacity of the city and providing effective protection for the war. Nowadays, there are problems with insufficient space utilization and unclear design concepts in the reuse of air raid shelters in the urban areas of Chongqing during the Anti-Japanese War. Therefore, specialized research on the adaptive reuse of air defense shelters in the urban areas of Chongqing during the Anti-Japanese War period is conducted. Based on relevant theories of adaptive reuse, firstly, by transforming and reusing the original functions and spaces of air defense shelters, the old functions is continued, the old functions is integrated with the new functions to expand the new functions. Secondly, the existing wartime air defense voids should be designed for adaptive reuse by expressing regional characteristics, optimizing internal spatial forms, showcasing ecological landscapes, upgrading functional efficiency, and enhancing safety performance, in order to improve and extend the efficiency and lifespan of wartime air defense voids. Finally, based on the unique regional characteristics of wartime air defense shelters, a diversified integration plan, a combination of civil defense functions and disaster prevention and rescue, and an adaptive reuse design strategy that integrates military and civilian functions are proposed, in order to better leverage the cultural and socio-economic benefits of air defense shelters in the Chongqing urban area during the Anti-Japanese War in the context of peace and war integration.

During the long-term operation of salt cavern gas storage, the duration of pressure changes within the reservoir is relatively long, and the frequency of pressure changes is relatively low. The deformation process of the reservoir's surrounding rock is a creep deformation process under low-frequency cyclic loading. To deeply study the mechanical properties of salt rock under long-term creep conditions, three sets of uniaxial creep tests on salt rock were conducted. The test results show that: (1) For damaged salt rock samples, the deformation process is divided into three stages: decelerated deformation, stable deformation, and accelerated deformation. The corresponding stress-strain curve exhibits a trend of "sparse"-"dense"-"sparse". (2) Among the two influencing factors of loading rate and stress upper limit, the stress upper limit has a more significant impact on the mechanical properties of salt rock. Under the same stress amplitude, as the number of cycles increases, the impact of different loading rates on salt rock deformation gradually decreases. (3) During the loading stage, the deformation rate of the salt rock samples gradually decreases over time until the stress increases to 60% of the stress amplitude, at which point the strain rate starts to increase. (4) In the constant stress upper limit stage, the strain rate gradually decreases over time, but significantly increases when the sample is close to failure. (5) Throughout the test process, the strain rates during different cycles are nearly equal in both the loading stage and the constant stress upper limit stage. In the final cycle before sample failure, the strain rate in the constant stress upper limit stage increases noticeably. (6) In the unloading stage, the deformation rate increases as the load decreases, with the elastic strain of the salt rock recovering in this stage, showing a negative deformation rate. (7) During the constant stress lower limit stage, the strain rate is close to 0 and fluctuates in a negative value state.

Tunnels crossing fault zones are common in railway engineering, water conservancy engineering and highway engineering. Engineering geological disasters induced by crossing fault fracture zones account for more than 50% of the total number of tunnel disasters in China. Ensuring the safety and stability of tunnels crossing fault zones is the top priority in the development of tunnel engineering in China. Based on the engineering background of Tabaiyi Tunnel, this paper explores the effective support measures of surrounding rock under the influence of fault fracture zone. In order to solve the problem of large deformation of soft rock in Tabaiyi Tunnel, this paper first explores the main controlling factors of large deformation by carrying out on-site point load test, in-situ stress test and indoor mineral composition analysis test. Then, according to the deformation mechanism of Tabaiyi Tunnel, a high pre-tightening force and long-short NPR anchor net support scheme is proposed. According to the excavation compensation theory, the high pre-tightening force of NPR anchor cable is used to compensate the stress of tunnel surrounding rock. Through numerical simulation and field monitoring, it is shown that the tunnel can effectively reduce the large deformation of surrounding rock under the influence of fault fracture zone under the high pre-tightening force and long-short NPR anchor net support scheme. The research results can provide reference for tunnel support crossing fault zone.

The excavation of tunnels in clay-altered rocks, formed through long-term geological and hydrothermal interactions, often results in disasters. It is challenging to identify and prevent these disasters during the excavation in clay-altered rock. To address these challenges, this study first analyzes 12 typical tunnel cases in clay-altered rock. The results reveal that clay-altered rocks can be classified into three types: vein-type, full-section-type, and pocket-type. Collapse incidents are prone in vein-type altered rock. Excavation in full-section-type rock exhibits substantial deformation of soft rock, easily leading to tunnel blockage caused by catastrophic collapse. The pocket-type is prone to large collapses and may encounter water and mud/rock inrush disasters when groundwater is abundant. Subsequently, methods for risk identification of the three types of altered rocks are proposed. Risk identification for vein-type rocks is based on the width, density, and angle with the tunnel axis of the alteration zone. The Global Altered Index (GAI) is proposed from the thorough hydration products of surrounding rocks and is used for risk identification of full-section-type rock. Risk identification for pocket-type rocks relate the filling material in pocket-like rock cavities. Clay-altered rock zones serve as excellent water transportation channels and water storage zones. Risks are exacerbated by the hydro-mechanical coupling mechanism in altered rock. Advanced geophysical exploration combined with borehole exploration can effectively prevent excavation risks. Proactive drainage, strong support, and closely following the second lining are essential for the smooth excavation process. The research results provide a scientific basis and technical support for the identification and prevention of risks associated with tunnel excavation in clay-altered and weathered rock formations.

To elucidate the variations in non-limit state earth pressure for limited soils mass under the rotation at the top of a rigid retaining wall (RT) mode, and to address the incomplete consideration of wall displacement, horizontal shear stress, and other influencing factors in existing earth pressure calculation methods, a numerical calculation method for passive earth pressure of a finite soil mass was developed within the framework of the differential element method. This method integrates considerations of wall displacement, soil strength parameters (c_m-φ_m), soil arching effects, and the impact of horizontal shear stress. By combining triaxial unloading tests and stress Mohr circles, the relationship between soil strength parameters (c_m-φ_m) under non-limit states and wall displacement was derived. Based on the principles of soil arching effect, stress analysis of the finite soil body was conducted, and static equilibrium equations for differential soil elements were established, further creating a numerical iterative format for passive earth pressure within a depth range. The proposed method was validated for its rationality and accuracy through comparisons with existing research. The results show that the lateral constraints under the RT mode help enhance the soil's shear resistance; Non-linear distribution of passive earth pressures along depth in finite soils; the magnitude of earth pressure decreases with a reduction in soil strength parameters (c_m-φ_m), a decrease in the initial slip surface angle, a reduction in the bottom of wall displacement ratio, and an increase in the width-to-depth ratio. The method of this paper can provide theoretical guidance for the economic design of retaining structures in practical engineering.

In order to enhance the safety and efficiency of pedestrian-vehicle evacuation in underground parking lot fires, a background field model based on cellular automata is constructed using Python. The model incorporates fire field data of the PyroSim simulation to create a dynamic coupling model of fire and pedestrian-vehicle evacuation. A simulation study is conducted in the underground parking lot of a commercial complex in Xi'an. The results show that, compared to pedestrian evacuation, the Required Safety Egress Time (RSET) for pedestrian-vehicle evacuation is extended by 20% to 130%. Safe evacuation is only achievable under specific conditions of pedestrian density and parking space occupancy. The arch effect is observed at the exit when pedestrian density is high, which reduces the evacuation efficiency of both pedestrians and vehicles. The probability of vehicle evacuation failure is approximately 22 times higher than that of pedestrians. Even if pedestrians successfully reach the exit, 15% to 25% still suffer from varying degrees of injury, with the proportion of serious injuries and near-death cases positively correlated with the pedestrian evacuation density. These findings can serve as a reference for optimizing fire protection design in underground parking lots and formulating evacuation plans for both people and vehicles.

The elderly water supply pipelines rehabilitated with cured-in-place-pipe (CIPP) technology can withstand internal water pressure loads. However, the existing pipeline's hole defects provide seepage channels for groundwater around the pipe, leading to a significant increase in local static water external pressure and causing instability and failure of the lining. Through static water external pressure tests and finite element analysis of two full-scale pipeline groups, DN 600 and DN 1000, this study investigates the deformation patterns and instability characteristics of the cured lining under the influence of static water external pressure. It explores the influence of lining DR values and ellipticity on the buckling behavior of the inner lining under interface bonding conditions. The results indicate that: The inner lining undergoes five stages under static water external pressure: uplift, bending, ultimate external pressure buckling, local fiber fracture, and lining fracture. The bonding strength of the interface significantly affects the buckling of the lining. When repairing water supply pipes using CIPP technology, it is essential to ensure the durability of the bonding performance and bonding effect between the CIPP lining and the existing pipeline.

Excavating tunnels within the influence range of goaf area poses significant technical challenges commonly encountered in underground construction projects. Considering the Baiyunshan Tunnel as the project backdrop, FLAC3D was utilized to analyze the stability of the tunnel under conditions that if the goaf area was filled with water or not. Then optimize the original support plan to suit different conditions. The results show that: Excavating the tunnel without grouting in diverse engineering conditions presented significant safety hazards. Stress concentration occurred at the left end of the goaf, resulting in a wide range of plastic zone above the tunnel and extensive damage to the tunnel. The vertical displacement of the tunnel floor was expected to surpass the prescribed control value that outlined in the pertinent guidelines. The presence of water in the goaf exacerbated the rock softening and damage. High pore water pressure posed a significant risk of water inflow into the tunnel's crown. For the tunnel that underpassed dry goaf area, grouting was carried out within a range of 140° when the distance between the goaf and the tunnel was less than 4.5 meters. Grouting was applied to the entire surrounding area when the distance between the goaf and the tunnel was within the range of 4.5~9 meters. If the distance exceeded 9 meters, grouting was not required to meet safety regulations. During the construction of the tunnel underpassing water-bearing goaf area, it was necessary to extend the grouting range to cover a distance of 4.5~10 meters from the goaf to the tunnel. Other parts of the tunnel could be supported in the same way as the tunnel that underpassed dry goaf area. The field monitoring results indicated that the stability of the tunnel had been ensured.

A large area of deep coastal soft soil layer is widely distributed in the coastal area. It has the remarkable characteristics of 'three-high, two-low, and one-long characteristic' with high water content, high compressibility, high organic matter content, low bearing capacity, low permeability, and long deformation stability time. Solidification treatment is one of the most used and most effective methods. An in-depth understanding of the solidification mechanism, strength characteristics, and durability of solidified soft soil is crucial for ensuring the long-term safety and stability of solidified coastal soft soil foundation. The strength and durability of the cement solidified coastal soft soil are reviewed. The multi-scale coupling solidification mechanism of cement on coastal soft soil is clarified. The shortcomings of the current research on solidified coastal soft soil are discussed, and the potential research suggestions with cutting-edge are discussed, which provides new thoughts and ideas for the follow-up scientific research and engineering application.

In practice engineering, it is commonly using pumping tests to determine hydraulic parameters, but the previous of estimated parameters cannot be proved due to the lack of unified standard and hard to choose a suitable algorithm. Meanwhile, due the limitation of independent algorithm, in some difficult hydraulic models, the engineers have to adjust parameters continually to meet the convergence criterion which cost lots of time and the accuracy of results cannot be proved. In this study, a series of pumping tests has been conducted in Dongli district of Tianjin city, China. With considering storage effect in the pumping wells and observation wells which has important impact in the early experiment, the effective ration has been proposed to eliminate the effect of well storage. Based on the local hydrogeological environment and measured drawdown, an unsteady leaky seepage model, called Hantush-Jacob model, is used to estimate hydraulic parameters. By combination of measured drawdown and analytical solution,three methods, extend Kalman filter algorithm, LM algorithm and Genetic algorithm, are all adopted to estimate hydraulic parameters in this study. According to the result, three algorithm all shows its limitation in the calculation. Thus, a combination of Genetic algorithm and LM algorithm has been proposed in this study. Based on the result, the combination algorithm shows its superiority in searching the optimal solution accurately and avoiding the defect of the three separate algorithm. According to the comparison, the measured drawdown fit well with the calculated drawdown based on the estimated hydraulic parameter. Furthermore, compared with the single algorithms used in previously published literature, the combined GA-LM algorithm has demonstrated its unique advantages in the inversion of hydrological parameters.

Discussing the development of the indirect boundary element method to the simulation of seismic dynamic interaction between river valleys and tunnels under Rayleigh wave incidence. On the basis of verifying the accuracy of the proposed method, the influences of tunnel buried depth and valley width-depth ratio on the surface displacement amplitude and circumferential stress of the lining tunnel under the action of the Rayleigh wave with different frequencies are quantitatively analyzed. The results show that: With the increase of tunnel depth, the displacement above the tunnel gradually decreases, and the amplification effect of surface displacement gradually weakens. The influence of the ratio of width to depth of the valley on the displacement amplitude in the valley and on the right side of the valley is more significant. Under shallow burial conditions, the circumferential stress amplitude coefficient of the tunnel near the river valley can reach more than 10.0, showing a significant dynamic stress amplification effect. Under η=2.0 incidence, the amplitude-amplitude-amplitude-amplitude-is significantly affected by the valley width-to-depth ratio, but the amplitude-amplitude-effect is not obvious when the buried depth d=3.0a. The seismic design of the tunnel along the river should focus on the amplitude effect of tunnel stress under shallow buried low frequency.

Through the indoor unconfined compressive strength test, focusing on the influence of different stone content and fine-grained material proportion on its compressive strength. Combined with the XTDIC analysis system to obtain the strain and displacement cloud diagrams of the sample, and the qualitative and quantitative analyses is carried out. The results show that under static loading, the increase in strain leads to an accelerated rate of initial stress growth and a significant increase in peak stress, and the maximum increase of adjacent peak stress is 22.2%, after reaching the peak, the strain continues to increase while the rate of stress reduction slows down, and the residual stress rises; when the content of stone powder in the specimen is fixed and the stone content varies, the growth rate of initial stress is accelerated and leads to the elevation of peak stress. From the stress-strain curve analysis, it can be seen that the specimen shows the best mechanical properties and the smallest deformation when the stone content is 70% and the stone powder accounts for 80%; the specimen shows the worst mechanical properties when the stone content is 30% and the stone powder accounts for 20%. The effect of fractal dimension on the unconfined compressive strength after compaction was significant, and with the decrease of fractal dimension after compaction (the increase of stone content), the unconfined compressive strength increases first and then decreases.

In order to better evaluate the passive instability failure mode of shallow shield tunnel face in sandy soil stratum, the existing three-dimensional calculation model is improved to make the failure area closer to the real soil failure contour. Considering the friction between the upper and lower blocks, the limit support pressure calculation formula is established by using the limit equilibrium method. The finite difference software FLAC^3D is used to construct the numerical model, and the variation law and failure mode of the passive failure support force of the tunnel face are analyzed. The limit support pressure solution obtained by the theoretical model is compared with the solution obtained by numerical simulation and the existing passive failure theoretical model to verify the reliability of the model. The results show that: The proposed theoretical calculation model can meet the limit calculation of passive instability of the tunnel face. The limit equilibrium method is used to calculate the friction between the upper and lower blocks of the model, and it is more reasonable to consider the static friction force. The optimal solution of the logarithmic spiral angle is affected by the internal friction angle. When the internal friction angle increases, the optimal solution of α will become smaller. The passive limit support pressure of the tunnel face of the shallow shield tunnel increases with the increase of the internal friction angle of the soil and decreases with the increase of the tunnel diameter.

Earth pressure balance shield tunneling is prone to spewing during excavation under conditions of large burial depth and high water pressure. Polymers are generally used as emergency modifiers to deal with spewing. Due to the high cost of polymers and the need for specialized mixing equipment on the ground to mix them into aqueous solutions, there are few cases of their application in soil conditioning. In order to explore the adaptability of water-soluble polymer in improving the formation of medium coarse sand, polymer soil conditioning was carried out for medium coarse sand with different fine-grained contents. Pressure permeability tests, critical spewing pressure tests, and flowability tests were carried out. The results show that: The permeability coefficient of improved soil is greatly affected by changes in fine particle content, while the effect of polymer addition on its permeability coefficient is relatively gentle; The flowability and critical surge pressure of the improved soil increase linearly with the increase of fine particle content; Exploring the adaptability of water-soluble polymers to the improvement of medium coarse sand residue from three aspects: permeability coefficient, critical spewing pressure, and flowability, and determining that polymers are suitable for medium coarse sand formations with a fine particle content of up to 4%; Comparing the economic benefits of the polymer with commonly used bentonite slurry, the results show that the polymer not only has a small impact on construction efficiency but also has certain cost advantages.

China preliminarily completes the transition of limit state design method for railway tunnel currently and establishes the limit state design method for railway tunnel structure under self weight and surrounding rock load. However, detailed research are not conducted on the limit state method for railway tunnel under seismic load. In order to improve the limit state design system of railway tunnel, clarify the target reliability index of railway tunnel structure for seismic resistance and establish the limit state method for railway tunnel for seismic resistance, the paper calibrated the reliability of railway tunnel lining and open cut tunnel in current general reference maps for seismic resistance by calibration method, and put forward the target reliability index of railway tunnel for seismic resistance based on calibration results. The results show that: The reliability index of railway tunnel structure for seismic resistance is mainly related to the surrounding rock level and structure type, specifically, the reliability index of the lining is significantly lower than that of the open cut tunnel, and the reliability index of the structure under Grade V surrounding rock is significantly lower than that under Grade IV; After considering the weight coefficients of various structures under different surrounding rock levels, the average reliability index of railway tunnel for seismic resistance is 6.81, which is greater than target reliability index of 4.2 for railway tunnel structure under self weight and surrounding rock pressure, the reliability level of the current structure for seismic resistance is relatively high; Based on the calibration results of the current general reference maps of railway tunnel for seismic resistance and the target reliability index in current code, the target reliability index of railway tunnel for seismic resistance is determined to be 4.7 for Level 1, 4.2 for Level 2, and 3.7 for Level 3.

In the process of blasting rock breaking, the existence of joints and fissures in rock mass affects the blasting crushing effect. Some finite element numerical simulation software can realize the blasting rock breaking simulation of jointed rock mass, while it is difficult to realize the quantitative description of cracks. A numerical model of jointed rock mass was established using LS-DYNA software to analyze the obstruction and reflection effects of joint surfaces on explosion stress waves. The images of blast-induced cracks were binarized, and crack extraction from the binary images was achieved using the Hough transform method. Statistical results of the crack images were subsequently analyzed through the maximum likelihood estimation method. The results show that: The existence of joints seriously hinders the propagation of blasting stress wave, and the peak stress is reduced by about 60%. The rock mass between blast hole and joint is subjected to stronger stress superposition due to reflection, and the crushing effect is more remarkable; In the initial stage of explosion, the occurrence probability of small cracks is large, and at the end, it is dominated by long cracks. In this process, many short cracks expand into long cracks, and the distribution of crack angles is relatively average. The distribution of long cracks with joint angles of 45° and 60° is more uniform, and the extreme value is not obvious. When the joints are 15° and 30°, the crack development in the vertical direction is obvious. The Hough transform method realizes the quantitative result statistics of crack images in the numerical simulation results.

In order to enhance the microbial improvement effect of red mudstone filler,calcium lignosulfonate and basalt fiber were used as admixtures to cooperate with microorganisms to improve the red mudstone filler. The MICP mixing method was used to test the physical and mechanical properties of the red mudstone filler. The effects of different amounts of calcium lignosulfonate and basalt fiber on the unconfined compressive strength, failure characteristics, no-load expansion rate and disintegration resistance of the red mudstone filler treated by MICP mixing and their changing laws were studied through relevant experiments. The mechanism of calcium lignosulfonate-basalt fiber and microorganisms in the improvement of red mudstone filler was revealed. The results show that: (1) Compared with the MICP group, when the content of calcium lignosulfonate and basalt fiber is 3% and 0.2% respectively, the synergistic improvement effect of the sample is the best, the longitudinal wave velocity is increased by 39.49%, the unconfined compressive strength is increased by 134.55%, and the peak strain at failure is increased by 32.34%. The calcium lignosulfonate-fiber and MICP synergistic effect can significantly improve the compactness, strength, and deformation resistance of red mudstone filler. (2) After the addition of calcium lignosulfonate and basalt fiber, the no-load expansion rate of the red mudstone filler is reduced by 53.84%~73.07%, and the disintegration of the optimal content group sample is improved from moderate disintegration to no disintegration. (3) The mechanism of calcium lignosulfonate and basalt fiber synergistic with microorganisms to improve the red mudstone filler mainly includes three aspects: the cementing and filling effect of lignin polymer, the reinforcement effect of basalt fiber, and the synergistic promotion effect of calcium lignosulfonate and basalt fiber on MICP. The research results can provide new ideas for the improvement of red mudstone filler materials in high-speed railway subgrades.

The air shock wave generated by tunnel blasting will not only endanger the safety of workers and construction machinery in the tunnel, but also affect the stability of surrounding rock and lining structure. Reasonable control of the generation and propagation of air shock wave is important to ensure the safety of tunnel blasting construction. This article summarizes the research progress on the propagation regularities, harmful effects, prediction methods, and control measures of air shock waves in tunnel blasting in recent years, focusing on the propagation law and control technology of tunnel drilling and blasting shock waves. Several representative air shock wave overpressure prediction formulas were selected, the prediction accuracy of different formulas under different blasting conditions was calculated, and the applicable conditions of different formulas were analyzed. The research trend of tunnel air shock wave is prospected from the aspects of tunnel air shock wave overpressure prediction method, air shock wave evolution law research and air shock wave active prevention and control device.