As a common geomorphic form in karst areas, isolated peak plain area generally does not have the physical workload of investigation due to its steep terrain, so it is impossible to obtain parameters such as uniaxial compression strength of rock, rock mass integrity, groundwater and weak structural plane. The classification of tunnel surrounding rock is mainly based on the rock strength and rock integrity as the main discrimination indicators, and the groundwater, the occurrence of weak structural planes and the initial test stress state as the correction indicators. Due to the lack of corresponding judgment basis, the basic classification of tunnel surrounding rock cannot be carried out, which is mainly based on experience. Through the analysis of the existing survey data, based on the liner karst ratio exposed by the drilling of the bridge construction site near the tunnel, and taking into account the regional karst development and the particularity of the location of the solitary peak, a calculation model of the volume karst ratio is established, and the tunnel surrounding rock is preliminarily classified in combination with volume karst ratio, karst development form and scale, karst filling, groundwater runoff and karst cave stratification characteristics as the main calculation parameters. According to the existing tunnel excavation experience in karst area, the relationship between volume karst ratio and the proportion of tunnel surrounding rock classification is established, which can better control the project cost for the design, construction and construction units.

The dynamic constitutive model of soil is one of the core issues of soil dynamics research, and it is the basis for carrying out dynamic numerical calculation of important civil engineering. The general dynamic constitutive model has many problems, such as many assumptions, small scope of application, and inable to reasonably reflect the dynamic characteristics of geotechnical materials. Starting from the viscous coefficient, through the big data deep mining of a large number of experimental data under the dynamic load of cohesive soil, the main influence coefficient of the viscous coefficient is determined, and the big data calculation model of the viscous coefficient is established. On the basis of the big data static generalized plastic mechanics constitutive model of the research team, the viscous coefficient calculation model was introduced into the viscoelasto-plastic model with the viscoelasto-plastic theory as the model framework, and the generalized plastic mechanics viscoelasto-plastic constitutive model of the big data cohesive soil was established. It has been proved that the fitting degree of this model is 0.956, which can better simulate the dynamic characteristics of cohesive soils under dynamic load.

Abstract：Because development and utilization of underground space resources is in the geological body, it is Influent by the nature and structure of the geological body and the state of storing of groundwater. This geological problems are state of storing of groundwater, the changing of groundwater water level. ground subsidence , active fault, covered karst collapse and the underground noxious gas. These issues may have adverse impact on the development and exploitation of underground space. An improper countermeasure might lead to heave losses. Therefore, geological condition should be considered as one of important factors when underground space planning is formulated. It is of great important to ward off risks, protect environment and achieve sustainable development.

Underground space resources (USR) are a new type of land resources with the dual attributes of resources and environment. The urban underground space resources (UUSR) are extremely precious, sensitive and irreversible resources which are carriers to the survival and development of modern urban. The development and utilization of UUSR must be scientific, in-order and reasonable. Besides, the assessment of UUSR is the basis and premise of UUSR utilization, unified control of national land space and three dimensional urban planning. In this study, the similarities and differences between land and mineral resources assessment, groundwater resource effect assessment and UUSR assessment are analyzed. The actualities, including progress and deficiency of UUSR assessment are discussed from seven aspects. The importance of strengthening UUSR assessment research and its connotation construction are discussed. Three key scientific issues of UUSR are discussed as the multi-scale effect of UUSR assessment elements, the mutual feedback mechanism between UUSR and its development and utilization, and the corresponding dynamic response of UUSR assessment elements. Meanwhile, the main contents of UUSR assessment are explored, and the future trend in five aspects are presented. Subsequently, the preliminary definition and corresponding concepts of the science of underground space resources (SUSR) are proposed. In addition, the basic framework and research paradigm of SUSR are presented.

Accurate evaluation of the geostress state and magnitude of engineering rock mass is an important prerequisite for underground engineering design, stability analysis and risk control. In order to clarify current situation of the theoretical study and engineering practice application of high geostress criteria, the direct or indirect influences of temperature, groundwater, tectonic movement, unfavorable geological condition, buried depth as well as the topography and geomorphology on the magnitude of geostress are detailed summarized. Several existing high geostress criteria are analyzed, combined with the latest research results, 18 kinds of geological markers of high geostress areas are summarized. The corresponding engineering phenomena and typical pictures of 13 geological indicators are further analyzed based on engineering phenomena, occurrence conditions and failure mechanisms. A reasonable evaluation of the universality of various criteria has been made, and it is pointed out that the strength-to-stress ratio criterion is a relatively authoritative criterion. Then, combined with engineering examples, the existing 6 calculation and classification methods of the strength-to-stress ratio method are compared. The most accurate strength-to-stress ratio criterion is dry uniaxial compressive strength ratio to maximum principal stress (UCS_drying/σ₁). Study results can provide references for the theoretical research and engineering practice of high geostress classification.

In view of some problems in the industrial standard " Technical standard for building engineering against uplift (JGJ 476—2019)", this paper presents understanding and thinking. For projects with anti-uplifting design grade A, this standard adds a lot of work content, among which the prediction of underground water level in the service period is a difficulty. The accumulation of basic data and the establishment of groundwater numerical analysis model are feasible approaches. It is not entirely appropriate for the standard to link the anti-uplifting design grade with the foundation design grade. In addition to the overall anti-uplifting stability checking calculation, the "unit anti-uplift stability checking calculation " for the weak parts of the underground structures should also be carried out, which should be considered in combination with the strength and deformation check of the floor. Under the condition of artesian water, the hydraulic head value of most areas of basement floor is the same as that of artesian water. The concept of cross section calculation formula of anti-uplifting bolt reinforcement is not clear. When adopting the active anti-uplifting method, the adaptability of stratum and environment should be fully considered. The problems of soil retention and clogging performance, seepage calculation of the drainage blind ditch and the durability of cutoff wall should be studied more deeply.

The rapid development of cities brings problems of “great urban disease”, such as environmental pollution, resource shortages, traffic congestion, ever-rising housing prices and so on. The best choice to solve the “great urban disease” is carrying out the development and utilization of urban underground space. This paper summarizes the characteristics of “great urban disease” in the construction of big cities in our country, puts forward the practical significance of development and utilization of urban underground space for urban sustainable development, then summarizes the development situation of urban underground space at home and abroad, and clarifies the core problems and the directions of development and utilization of urban underground space. Based on the analysis of the status quo at home and abroad, the paper puts forward the future development principles of China's development and utilization of underground urban space, meanwhile, from the perspective of practical thinking of China's development and utilization of urban underground space, puts forward certain development viewpoints of the planning layout of future underground cities: advocating the establishment the concept of the fourth land and underground red line from the perspective of legal construction; valuing ideas including combination design, planning with blank, intelligent construction from the perspective of planning, design, construction; proposing to adopt node TOD space layout concept from the perspective of space; adhering to the people-oriented concept from the perspective of sustainable development. The Research Summary and development viewpoints provide a reference for the future development of underground space planning, aiming at providing a new model for the linkage utilization of three-dimensional space of future large cities.

The mechanical parameters of rock mass are significant in slope stability analysis of open-pit mines. Hoek-Brown strength criterion can fully reflect the characteristics of nonlinear failure of rock mass and it is widely used in engineering practice. Structural plane is a part of rock mass, and how to estimate the shear strength of structural plane in an exact way is also a worthy question to explore. The GSI index was quantified by the contour curve and pressure-resistance test. Using generalized Hoek-Brown strength criterion to calculate the mechanical parameters of the rock mass in II-B slope of Hexing mine. According to the Barton-Bandis theory, the shear strength of structural plane and the stability of sliding rock mass were figured out. The calculation results showed that the safety factor of the slope is Fs=1.285, and the safety factor of the potential slip plane is Fs=0.911. That means the stability of the overall slope is well, but the partial rock mass has the potential to slip along with the structural plane. The analysis results are in accord with the actual situation. It is demonstrated that the strength parameters of rock mass and the shear strength of the structural plane obtained by this method are reasonable.

Shenzhen is China's special economic zone and one of the core cities of Guangdong, Hong Kong and Macao. Significant achievements have been made in Shenzhen's urban construction. With the urban ground space of Shenzhen becoming more and more limited, the development of underground space has become the inevitable trend. This paper first summarized the current status, the future planning and the existing deficiencies of underground space construction engineering in Shenzhen, such as underground transportation system (including underground rail traffic system and underground expressway), utility tunnel, underground commercial street and other underground municipal facilities. Secondly, combined with several typical underground space development projects which have been completed or planned in Shenzhen, the design and construction overview was introduced, and the difficulties and technical innovation in these projects were analyzed. Furthermore, based on the existing deficiencies in overall planning, development level, construction difficulty, policies and laws of the urban underground space utilization in Shenzhen, some thoughts and suggestions on the construction of urban underground space in Shenzhen were put forward.

Based on the seismic damage rehabilitation project of Daliang tunnel in Lanzhou-Xinjiang high-speed railway crossing seismogenic faults, through field investigation, mapping, exploration and other methods, the deformation and damage characteristics of the railway tunnel crossing the active fault zone under near-field strong-earthquake effect were revealed. Combined with the seismic safety assessment conclusions, the multi-dimensional repair methods of earthquake-damaged tunnel in active fracture zone was proposed, which included protection and reinforcement, structural demolition and reconstruction, reserving deformation space, applying devices for the energy dissipation and shock absorption, structure segment design, and using ballastless track with large adjustment. These repair methods possess the rapid and safe characteristic during the construction, which could solve the related problems caused by the further deformation of active fracture in the subsequent operation stage, so as to achieve the adaptive effect of post-earthquake residual slip and moisture slip deformation structure and rapid repair of stick-slip dislocation damage. According to the feedback of field construction and monitoring results, the relevant repair plans were highly feasible, and the repaired tunnel structure has a good carry capacity. This study can provide practical experiences and useful references for the earthquake disaster recovery and seismic fortification of subsequent similar tunnel engineering.

Choosing an appropriate constitutive model for soil is the key to ensure the quantitative accuracy of modeling geotechnical problems. In recent years, two kinds of models, i.e., the hardening soil model (HS model) and the hardening soil model with a small strain stiffness (HSS model) have shown the good validity and advanced nature in existing studies. There are, however, rare reports on their applications in engineering problems of loess. For this goal, in allusion to the laboratory triaxial compression test of loess and the field plate load test on the loess ground, the HS and HSS models as well as the commonly used Mohr-Coulomb model (M-C model) and Duncan-Chang model (D-C model) in the finite element software Diana were employed to carry out a comparison study of numerical modeling. The results show that the HS and HSS models are better than the M-C and D-C models in fitting the resuts of the two tests, and overall, the fitting results by the HSS model are better than those by the HS model. Therefore, the HS and HSS models are more reliable than the latter two in the aspects of modeling the deformation of loess as well as its mechanism of instability and failure, and are of the value to be popularized.

To analyze the relationship between microparameters and macroparameters of the uniaxial compression PFC2D model of rock, and to calibrate the microparameters, the orthogonal design and analysis of variance are adopted in this paper. Flat-jointed contact model is used as the contact constitutive model of particles. The orthogonal design is conducted to the microparameters of PFC2D model. Then analysis of variance and dimensional analysis is utilized to analyze the relationship between microparameters and macroparameters. On this basis, the process of trial-and-error method for calibration of microparameters for rock is proposed and is used to calibrate the microparameters of limestone. Simulation results of macroparameters, stress-strain curves and failure characteristics are closed to the laboratory test results, and this validated the significance of the suggestion for trial-and-error method. If a biaxial compression PFC^2D model need to build, the two microparameters (tan φ_b, μ_b) need further calibration. The research results can provide references for the particle flow simulation of rock mechanics tests.

Quickly identifying discontinuity of the rock in a tunnel face and interpreting its geometric and mechanical parameters are considered as important basis for realizing remote tunnel diagnosis. However, 3D point cloud recognition based on digital photos often relies on commercial programs. Based on the open source framework of AliceVision, this paper developed a microservice module for point cloud information recognition of discontinuity of rocks in a tunnel face. Encapsulated with the Django framework, the module can be flexibly deployed in a platform that supports the microservice architecture. With photos of the rock mass on the tunnel face taken from different perspectives and uploaded remotely by users, the microservice helps automatically identify 3D point cloud and achieve 3D reconstruction. Currently, the microservice module has been deployed infrastructure Smart Service System (iS3) developed by Tongji University. The results compared with those obtained from other software show that the microservice module can meet the basic need for 3D construction with advantage in the computational speed although effort is still needed to further improve the accuracy.

Rock abrasivity is one of the main factors affecting the wear of various tools in tunnel construction. Many small scale tests are designed for assessing rock abrasivity in the world. Among of these tests, Cerchar abrasiveness test, due to its ease of operation, has been prevalently used in the world. Its result, CAI (Cerchar Abrasivity Index) value, is capable to predict a normal tool wear which is steady and continuous. At present, the Cerchar test is widely used in China to assess rock abrasiveness. However, as the Cerchar test is lately introduced in China without a national test specifications, and CAI value classification remains unclear. This paper collectes five CAI value classifications used in the international laboratories and institutions. By discussing on hardness of stylus used to determine CAI value, tool wear corresponding to each CAI class and extensive testing results, we think that ISRM suggested CAI classification is the most reasonable one. This paper could be a reference to establish the Cerchar test specifications and evaluate rock abrasiveness in China.

The Cross-river Tunnel of the East Fuxing Road in Shanghai is the first double-deck tunnel in China. Horizontal Freezing Method was used to construct the cross- passages monitored with a system of information construction. Analyzing the monitored data in details, it is shown that the layout of freezing pipes and the heat radiation of tunnel lining are two important factors affecting the frozen soil's shape. The frozen soil's shape can be divided into three zones according to the lay out of freezing pipes and the heat radiation of tunnel lining. Through defining the radiating coefficient of the tunnel lining, the influencing degree and dimension affecting the frozen soil behind the tunnel lining due to the heat radiation are discussed. The significant conclusions obtained in this paper provide a good reference in guiding future design and construction in similar conditions.

Data center is an important part of promoting the whole society to be highly digitized and informationized. Its reliability and security are very important to the normal operation of the country or enterprise. Due to the high environmental sensitivity and high energy consumption, the location and energy saving of data center has always been the primary and key problem of the whole industrial chain. With the successful completion of some large tunnel type underground data centers in China, the advantages of underground data centers, such as high concealment, low energy consumption, anti-interference and low pollution, have gradually attracted people's attention. Compared with ordinary underground engineering, large underground data centers involve more complex majors and disciplines, and the operating environment is more severe. In view of the future development of data center in the direction of high standard, low energy consumption and green, this paper comprehensively summarizes the development and research status of underground data center at domestic and abroad, and analyzes the classification and related specifications, from the perspective site selection area and construction process, energy consumption demand and cooling technology, energy consumption demand and cooling technology, green data center, this paper summarizes and analyzes the development trend of data center and the characteristics of underground construction, and puts forward the problems and challenges faced by the construction of underground data center in four aspects: collaborative demand of energy saving and environmental control, suitability transformation of existing underground caverns, new underground caverns, intelligent early warning and prevention and control. The development and utilization of underground space is not only a simple space expansion, but also a functional demand. This paper aims to provide ideas for the construction of large underground data center in the future, and also hope to provide reference direction for the development and utilization of functional underground space.

Based on the statistical results of anchorage forms of 81 suspension bridges in China, the application status and development trend of tunnel-type anchorage were analyzed. Combined with relevant research data at home and abroad, the deformation characteristics, failure modes, and the calculation methods of pull-out forces were summarized. Four in-situ scale model tests carried out by our group in soft rock strata were introduced. The feasibility of constructing tunnel-type anchorage in soft rock strata was verified according to the test results. The key factors affecting the stability of tunnels-type anchorage in soft rock strata are clarified. The future studies are considered to be in the following five directions: (1) Study on the load transmision mechanism of tunnels-type anchorage in soft rock strata, and further research the failure mode and long-term stability of tunnels-type anchorage in soft rock strata. (2) The reinforcement measures to prevent the damage of tunnel-type anchorage are studied; (3) Understanding the stress state on the failure surface is the key to calculate the bearing capacity of the tunnel-type anchorage; (4) Combined with model test and discrete element numerical simulation to study the deformation-fracture-instability evolution process of tunnels-type anchorage.

In consideration of the development and construction of the Shanghai Hongqiao integrated transportation hub, introduced the overall layout and the underground space development program of the world's largest transportation hub - Hongqiao integrated transportation hub. At the same time, relying on the hub building, an analysis of the pivotal conditions of underground space development in the region had been done. The necessity and urgency of underground space development in Hongqiao integrated transportation hub region were studied. The objectives, principles and general ideas of underground space in Hongqiao integrated transportation hub region are proposed. Based on the study of functions and scale of underground space, the control requirements of underground space planning were given, and the suggestions on planning of underground traffic facilities, underground complex settings and underground space planning and implementation were recommended.

In order to reduce the error between the classical Coulomb's earth pressure theory and the vertical layered earth pressure in actual engineering, based on the traditional Coulomb's earth pressure theory and finite earth pressure theory, and considering the strength characteristics of unsaturated soil, the static equilibrium relationship of layered soil behind the retaining wall was established. The calculation formula of the active earth pressure of the vertical layered soil was obtained. By comparing with the existed theories, the reasonableness of the method in this paper was explained. The influence law of the filling property parameters and the retaining structure geometric parameters on the earth pressure are respectively analyzed. The research results show that the difference of the vertical soil layer has a great influence on the calculation result of active earth pressure. The active earth pressure of vertical layered unsaturated soil decreases with the increase of effective cohesion, effective internal friction angle and matrix suction, and increases with the increase of the grading angle of back wall and the slope angle of backfill surface. The change of the shear strength indexes of the filling near the back wall has a more obvious influence on the active earth pressure.

Microseismic monitoring technology is a high-tech and informationized dynamic monitoring technology for underground engineering.With the fast development of hardware,signal processing and digitizing technology,the applications of microseismic monitoring technology abroad become more and more.An applying research of this technology is coming up now in China.Combined with the research of the author in recent years,the characteristics of microseismic monitoring technology and its functions on application to underground projects are introduced briefly. Based on its applications abroad and at home, several applying aspects to safety monitoring of underground projects are summarized in this paper. An example of successful application of this technology in China is presented.

The performance of anchors relates to the safe operation of the vessel, the research of movement rules of the anchor in the sediment has been concerned by many scholars. The large deformation and failure of soil happened every moment in the process of dragging anchors, involved many mechanical behavior, such as material nonlinearity, geometric nonlinearity and contact nonlinearity, etc. So it may be difficult to study the dragging anchors through the general analytical research tools. In this paper,the physical model test was carried out used the model Hall anchor, and the movement characteristics and attitude variation of the anchor was measured in the dragging process. Then a numerical calculation model was established to simulated the model test based on the Coupled Eulerian-Lagrangian(CEL). The postural changes of the anchor with the dragged distance were depicted, and the buried depth of the anchor along with the horizontal displacement was plotted. The contrast of the numerical and measured results showed good consistency, which verified the reasonability of the CEL method on analyze the dragging anchors. This method can be used for the research and design of dragging anchors.

The scale of urban underground space use is getting larger, and the utilization of shallow underground space in central areas of some cities is even saturated, and the demand for deep underground space is becoming stronger. At the same time, the progress of underground project construction technology has made it possible to use deep underground. Urban deep underground space use at home and abroad is reviewed. Since deep underground space use take place first in the downtown area of the city, followed by a gradual movement to the city's periphery, and planning plays the important role of strategic guide and rigidity control, and is highest priority task for deep underground space use, and the three issues are proposed at planning level which are "unclearing for scientific law of using premise", "unknowing for using patterns and criteria" and "being uncertain forquantitative indicators of controlling and guidance".

Rock tunnel boring machine (TBM) is a safe, fast and effective tunnel excavation equipment. However, TBM is prone to get stuck when TBM is excavating complex and high in-situ stress tunnels. Therefore the influence of geological environment should be considered as much as possible at the beginning of TBM design to reduce the risk of TBM sticking. By analyzing the influences of high stress conventional stratum and high stress soft and broken rock stratum on TBM, two criteria of TBM jamming in high stress conventional formation and high stress soft broken formation were proposed. According to the two criteria, the theoretical calculation method of shield length design and thrust design of high stress tunnel TBM considering surrounding rock mechanical parameters was proposed, and the basis of parameter selection was given. Finally, the rationality of the existing TBM design was calculated and analyzed based on actual surrounding rock geological parameters of a high stress tunnel in Southwest China. The study can provide basis for the design and calculation of shield length and thrust of TBM.

According to the development process of underground space, this paper summarizes the new thinking from underground space 1.0 to underground space 5.0. The basic characteristics were discussed explicitly during the development of the underground evolution. The key technologies and typical cases from underground space 1.0 to underground space 5.0, then the characteristics and mechanism of the underground space development were revealed in the end. The research shows that the overall form of underground space is from "one underground point" to "one underground line", and then weaves "one underground network". The scale is becoming larger and larger. It is built into "an underground city" through the advanced concepts of aboveground and underground three-dimensional planning and regional overall development. With the development of artificial intelligence, digital twins Cutting edge technologies from green low-carbon to carbon neutralization are gradually widely used, and will eventually be transformed and upgraded into "smart three-dimensional city" and "green underground space" in the foreseeable future.

Abstract：Combined with rock slope engineering examples, the analysis of the calculation methods for anchors axial force in rock slope was carried out in different ways. The results show that the calculated values of bolt axial force by limit equilibrium method, the strength reduction method, equivalent internal friction angle method, 2-D numerical analysis method are relatively large. The calculated values by 3-D numerical analysis method are reliable. It is consistent with the result from actual slope. The calculated values of anchors axial force by lateral rock pressure calculation method and unbalanced thrust method are almost the same with that by numerical analysis method. When the lateral pressure is close to zero, the calculation design method in technical code for building slope has potential safety problems. In this case, the strength reduction calculation method is proposed in this paper. Through a series of case studies, the applicability of the proposed method was clearly exhibited. Anchors axial force is not uniformly distributed, the anchors should be strengthened on the top and the bottom of the slope. The slope which has a good stability during the construction phase can be treated by direct construction method, because the stability of the slope has been fully used to reduce the anchors axial force, and also can optimize the designs.

The occurrence of mine dynamic disaster is often accompanied by coal rock failure. Study on the evolution characteristics of coal rock fracturing can provide a theoretical basis for the monitoring and early warning of mine dynamic disaster. Four typical coal rock samples, including coal, mudstone, sandstone and shale, which are common in coal measure strata of a mine, are selected for uniaxial compression tests to study the acoustic emission characteristics of their failure process. The results show that: The ringing counts can precisely reflect the failure law of coal and shale samples in each stage, and the increasing inflection point of cumulative ringing count curve appears at the beginning of plastic stage. In the failure process of mudstone and sandstone, the ringing count is less, and the inflection point of the cumulative ringing count curve appears in the late plastic stage. The failure modes of the four coal rock samples are mainly tensile failure and the average proportions of tensile failure of coal, mudstone, sandstone and shale samples are 64.97%, 73.12%, 84.45% and 92.21%, respectively. The number of peak frequencies of each frequency band shows a sudden increase before the failure. The main fracture frequency of coal and sandstone is Ⅲ (150~200 kHz), mudstone is Ⅰ (50~100 kHz) and Ⅴ (280~330 kHz), and shale is mainly concentrated in Ⅱ (100~150 kHz) and Ⅴ (280~330 kHz). The acoustic emission b-value of the four types of coal rock generally show the characteristics of "uptrend - fluctuation - decline stage". The b-value can effectively reflect the fracture process of the four kinds of coal rock, and the decreasing trend before the failure can be used as an important precursor information of the failure and instability of coal rock.

Under the condition of the tension of land resources, the development and utilization of underground space will be the inevitable trend of future residential construction, and the planning of three-dimensional residential area will become the focus of “energy conservation and land conservation” in the future. Combined with the problems existing in the development of underground space in domestic residential areas, this paper systematically studies the development and utilization mode of underground space in residential areas from three aspects of spatial structure, spatial function and spatial form. On one hand, the suitability of various functional Spaces and service facilities in the underground space of residential area have was analyzed; On the other hand, the layout pattern, basic structure form of and the characteristic theme development mode of residential underground space are proposed. Finally, the comprehensive development strategies of residential underground space are summarized from three aspects of the the cooperative development of aboveground and underground space, the interrelation of residential underground space and the sustainable development and utilization of residential underground space, so as to explores the planning and development of the underground space for the future high-density urban residential area.

Abstract: According to the current situation of People’s Square underground space: three metro lines can be interchanged here; more than fifty bus lines gather here; many commercial, cultural, underground parking facilities are distributed here. The future requirement analysis of People’s Square shows that the present situation of the square can not meet future development requirement. So the successful experience of San Francisco and Montreal can be used in combination with the practical situation of Shanghai People’s Square. This paper presents some ideas of optimization of people’s square underground space: shortening time of metro interchange; integrating metro and bus interchange; connecting the function buildings in this district.

How to couple fluid flow and mechanics is very crucial in numerical simulation for water-air two-phase fluid-mechanical interaction in saturated-unsaturated soil. The loose coupling has the advantages of being relatively simple to implement and with higher accuracy. Thus the loose coupling algorithm is one of the main ways for coupled fluid flow and mechanics modeling under multiphase flow conditions. This paper presents the loose coupling scheme for simulating water-air two-phase fluid-mechanics interaction, in which TOUGH2/EOS3 is employed to model the water-air two-phase flow process, FLAC3D is conducted to analyze the mechanical process, and two codes are linked and sequentially executed through external coupling modules by C++ computer language. The coupling relationships for linked TOUGH2-FLAC3D simulations are presented, including relationship between saturation and soil density, effective stress function depending on both liquid and gas pressure, corrections of porosity, permeability, and capillary pressure for changes in stress. The accuracy and efficiency of linked TOUGH2-FLAC3D simulator are verified by simulating an in-situ air flow test in Essen and comparing the measured and calculated values of surface placement and air losses.

As the key index of geotechnical engineering investigation, soft soil parameters are the premise and basis for studying soft soil characteristics and solving soft soil engineering problems. Taking the deep soft soil in Nansha port area of Guangzhou as the research object, 371 groups of indoor geotechnical tests and 147 groups of field in-situ test data were collected, and the spatial characteristics of soft soil parameters are studied by mathematical statistics and random field theory. The results show that: Soft soil shows "four high and one low", to be specific, high water content, high liquid limit, large void ratio, high compressibility and low shear strength, it has strong regional and spatial heterogeneity, and the space-time effect is significant; The empirical formula between soft soil parameters are established, it is showed that the physical indexes of soft soil have better stability, smaller coefficient of variation and stronger correlation than the mechanical indexes; The water content, void ratio, compression coefficient, liquid limit and liquid-plastic limit index decrease with the increase of soft soil depth, while natural density, compression modulus, strength index and static cone penetration index increase slowly, the shear strength of vane first decreases and then increases; The autocorrelation distance has no obvious correlation with the increase of exploratory hole depth, the cone tip resistance index can better reflect the spatial variation characteristics of soil layer and the reproducibility of test results, and realize the transformation of soft soil parameters from "point" characteristics to "spatial" characteristics; The recommended value of soft soil judgment standard in this area is put forward, which provides a reference for the survey and design, soft foundation treatment and construction of silt soft soil in similar areas.