Volume 14 Issue 6
20 December 2018
  
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  • Methods of the General Layout Planning of Underground Pedestrian Passageway
    Tao Weisheng, Ruan Xiaoping
    Chinese Journal of Underground Space and Engineering. 2018, 14(6): 1431-1436.
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    The general layout planning of underground pedestrian passageway is an important part during the process of urban underground space utilization planning. One of the content is the general layout of underground passage over street, the other one is planning guidance of underground pedestrian streamline organization in the priority areas. The analysis foundation of the content is delimiting the underground pedestrian connecting priority areas. So the general layout planning methods can be divided into three steps in the actual terms. Firstly, delimiting the underground pedestrian connecting priority areas with value partition evaluation method; secondly, arranging overall layout of underground passage over street with demand distribution method; thirdly, making a pedestrian network system and ensuring the streamlines continuation by refining detailed placement of underground passage and underground pedestrian connection passageway.
  • Evaluation of Underground Space Development in Historical District Based on AHP
    Zhu Yinge, Zhao Jingwei, Huang Ziyu
    Chinese Journal of Underground Space and Engineering. 2018, 14(6): 1437-1444.
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    Based on the basic theory of historical district protection, this paper analyzes the protection and development of historical district. By analyzing the natural conditions, ground and underground space conditions, geographical conditions, historical research conditions, living conditions and so on, the historical district underground space evaluation index system was established. Through expert survey method, the indicators of the index system were initial scored, and the weight of the consultation value was got by means of statistical analysis. The weights of each influencing factor were determined by using analytic hierarchy process (AHP), and the evaluation model of underground space was built. It clarified the classification standard and development mode of underground space development in historical district, and the value of underground space development was evaluated by taking the historical district of the Zhongshan Road in Qingdao as an example.
  • Urban Underground Composite Pipe Gallery Construction Based on BIM and IOT Technology
    Chen Shu
    Chinese Journal of Underground Space and Engineering. 2018, 14(6): 1445-1451.
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    Urban underground composite pipe gallery is of great significance to the construction, operation, maintenance and security of city pipeline. Taking urban underground composite pipe gallery construction in Pintan as an example, for the defects of long construction period and environmental pollution of traditional construction technology in underground composite pipe gallery, here to puts forward a recycling support technology of the rigid-flexible, compound and impermeable character, as well as prefabricated assembly technology, to shorten construction period and reduce environmental pollution, to realize the concept of green construction project. At the same time, on the basis of BIM technology and the IOT, through the monitoring system of composite pipe gallery, we set up its data platform with precise control and management, significantly reduce the artificial operation error, to realize object-linking, information sharing and exchange function, to solve the problem of data chain broken and inefficient management during the full life cycle phases of the project, then to realize the wisdom of the urban underground pipe gallery intelligence and information operations.
  • A New Method for Determination of Uniaxial Tensile Strength of Rock through Bending Test
    Lü Aizhong, Wang Haoyu, Cai Hui
    Chinese Journal of Underground Space and Engineering. 2018, 14(6): 1452-1457.
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    The uniaxial tensile strength of rock is an important mechanical parameter. The four-point bending test method is an indirect method for obtaining the uniaxial tensile strength of rock. But the uniaxial tensile strength calculated by the traditional formula of the four-point bending test is often much greater than the actual uniaxial tensile strength, and sometimes is even 2~3 times the tensile strength of the direct tensile test. Therefore, it is necessary to improve the traditional formula to derive a new tensile strength calculation formula, and obtain a uniaxial tensile strength that is in line with the actual one in the four-point bending test. On the basis of different tension and compression modulus of rocks, the plastic deformation behavior before rock failure is considered, and the uniaxial tensile strength calculation formula of the four-point bending test is accurately deduced by the elasto-plastic mechanics method. The results of the new tensile strength calculation formula were analyzed and the uniaxial tensile strength of the rock, which was in line with the actual situation, was obtained.
  • Mechanical Characteristics Analysis of Surrounding Rock of Unilateral Expansion Tunnels in Situ
    Yang Bin, Lin Congmou, Zhang Zaicheng, Yin Rongpeng, Wen Zhijie
    Chinese Journal of Underground Space and Engineering. 2018, 14(6): 1458-1465.
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    In order to analyze the mechanical characteristics of tunnel side wall rock mass by means of analytical calculation, considering the tunnel lining plays an important role to keep the stability of surrounding rock in practical engineering, according to the analysis of the existing tunnel surrounding rock mechanics solutions, in the case of considering supporting force, combined with Schwarz alternating method, a calculation analysis algorithm of the surrounding rock deformation was provided. Construction between the surrounding rock deformation monitoring data and ABAQUS numerical simulation of the Damaoshan tunnel engineering show: in the case of considering support, tunnels expansion in situ Schwarz alternating method can get more precise surrounding rock mechanics properties of the expansion tunnel, the method has a better applicability. With the enlarging widths of the tunnel, its features are as follows: (1) At the tangent place of hole1 and hole 2 i.e. excavation construction part, the stress changes of the original tunnel is bigger. At the hole 2 i.e. expansion digging part, hoop stress has tensile stress in the vault. (2) Along the vertical, horizontal displacement of the original tunnel values change little, which is relatively stable. At the digging part, the vertical displacement has increasing trend, expanding horizontal displacement has a trend of convergence. (3) Compared with no supporting force, when there is supporting force, the tunnel expansion horizontal displacement tends to be stable, and the vertical displacement change is smaller.
  • Theoretical Calculation Method of Tensile Deformation Modulus of Damaged Rock
    Shen Caihua, Wang Haoyue, Li Xuesong, Wang Yuan
    Chinese Journal of Underground Space and Engineering. 2018, 14(6): 1466-1475.
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    The essence of tensile rock failure is the propagation of micro cracks. Assuming that the uniform damage of rock sample consists of many single cracked rock units, the strain of crack in rock unit under the condition of tensile including elastic strain and inelastic strain caused by crack opening, elastic strain caused by rock matrix. Calculating crack opening displacement with COD theory, and by which we can calculate the strain increment of rock element. The relationship between rock tensile failure strain and the initial crack density and crack spacing was calculated, and the calculation method of damage rock specimen's bulk modulus of deformation under the condition of tensile was finally established. The method can effectively describe the influence of the initial crack number and the crack length on the rock deformation, which is more accordant with the actual conditions. Combined with example analysis shows that: the strain caused by the crack opening (including elastic and plastic parts) is an important part of the deformation of damage rock, and the initial damage coefficient and internal tensile strength is directly proportional to the strain, and elastic modulus of rock matrix is inversely proportional to the strain. The deformation modulus of rock decreases with the increase of initial damage of rock, and decreases with the increase of crack length damage factor. And the initial damage coefficient is proportional to the initial crack density and the square of the maximum half length of the crack.
  • The Validation of the Effective Stress Principle of Unsaturated Soils
    Shao Longtan, Qin Yalong, Guo Xiaoxia, Zheng Guofeng, Zeng Lifeng
    Chinese Journal of Underground Space and Engineering. 2018, 14(6): 1476-1483.
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    The effective stress principle of unsaturated soil is significant to the development of unsaturated soil mechanics. Although there are many kinds of the existing formula of effective stress for unsaturated soil, it is difficult to find the formula which combine some theoretical basis and clear physical meaning, what's more, it is necessary to further verify its application. For the purpose, the evolution of the effective stress principle of unsaturated soils were summarized briefly in the first and then the theoretical basis and physical significance of several typical formulas about the effective stress principle of the unsaturated soils were discussed. By comparison, it is found that the effective stress formula derived from the theory of continuum mechanics by Shao L T was similar in form to the semi-empirical formula proposed by Vanapalli in 1996, but the formula raised by Shao revealed that the effective stress was the skeleton stress due to all the external forces excluding pore water pressure. Finally, the formula was aligned with the four parameters Van Genuchten model to predict the strength of expansive soil, silty clay, clay sand and adobe soil. The result indicates that there is a well agreement between the theoretical value and test result within the scope of the test accuracy. Thus it validates the feasibility of the formula used in the tests and projects.
  • Laboratory Experimental Study of Slaking Characteristics of Coal Measure Strata Soft Rock
    Zheng Mingxin, Zhang Hanqiu, Shu Mingfeng, Fan Yakun, Yang Jikai
    Chinese Journal of Underground Space and Engineering. 2018, 14(6): 1484-1489.
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    Due to the coal measure strata soft rock is prone to softening and disintegrating, based on the test of collapsing in laboratory of different block of coal measure strata soft rock, the slaking durability index and the variation of shape and size of slaking pieces of soft rock under wet and dry cycles were discussed, and the reason of disintegration was analysed. The results are as follows: (1) the decrease of coal measure strata soft rock slaking durability index follows an exponent relationship with the increase of slaking cycle times. The index was mainly decreased in previous three cycles, the largest decline is caused by first circulation. (2) The slaking pieces of different block of coal measure strata soft rock can be named as bad graded sand. The grain contents between 0.5mm~5mm could reflect the rate and degree of slaking obviously, so the above particle size range is suggested to be an evaluate standard to the slaking stability of coal measure strata soft rock.
  • Experimental Study on Rock Damage Characteristic of the Key Zone for Collapsed Rock Mass
    He Kai, Li Bin, Zhu Sainan, Gao Yang
    Chinese Journal of Underground Space and Engineering. 2018, 14(6): 1490-1497.
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    Acoustic emission experiment and numerical experiment were carried out for solving the problem of damage-induced deterioration of the key zone at bottom of high-steep unstable rock mass. Based on damage theory, damage characteristic and its development tendency of rock samples were analyzed by the data from experiments, such as stress, strain and parameters of acoustic emission. The result shows that these rock samples present typical failure characteristics of brittle. With concentrated release of energy, acoustic emission count suddenly increased when the main fracture appear. The frequency of acoustic emission increases and the silence period becomes shorter as the confining pressure goes up. The curve of accumulated acoustic emission count increases gently, gradually, sharply in early stage, middle stage and later stage, respectively. It is consistent with the stress-strain curve. Damage variable was built based on the accumulated acoustic emission count. This damage characteristic can be used to make quantitative analysis for the damage development of the rock samples and the key zone of rockfall during failure process. The research can serve as an important reference for the damage characteristic of the same type of rockfalls.
  • Experimental Study on Time Effect of Seepage Properties of Marble Fracture
    Wang Chenlin, Guo Baohua
    Chinese Journal of Underground Space and Engineering. 2018, 14(6): 1498-1504.
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    Single fracture seepage tests under different normal stress were conducted by self-developed radial flow device for coarse-grained marbles with single tensile fracture, and the effect of the normal creep of rock joint on relationships between flow rate and normal stress, inlet water head were analyzed respectively. The results show that the fracture creep closure showing the characteristics of initial creep stage obviously increases and has an logarithmic relation with time under a constant normal stress; there is a positive linear relationship between flow rate and head difference in either head-decreasing stage or head-increasing stage; the normal creep of rock fracture led to conductive capacity of rock fracture decreasing with the increase of time under the constant normal stress, therefore, the flow rate difference between head-decreasing stage and head-increasing stage under the same water head increases with head difference; flow rate of fracture follows a negative exponential function with the normal stress in the head-decreasing stage and head-increasing stage under the same head difference; the flow rate difference between the head-decreasing stage and head-increasing stage under the same normal stress decreases with the normal stress, the reason is that fracture creep closure has a positive linear relationship with normal stress. The research results have some referencing value for the engineering application in rock fracture seepage.
  • Experimental Study for Destructive Zone of High-strength Mortar Material under Explosion Effect
    Wang Qirui, Kong Fuli, Fan Junqi, He Yongsheng
    Chinese Journal of Underground Space and Engineering. 2018, 14(6): 1505-1511.
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    High-strength mortar concrete materialwas used to simulate the rock with same strength. Research on the damage effect of TNT explosives on simulated rock media under incomplete closed explosion conditions was carried out. The scope of destruction zone was determined by three methods including macro-phenomenon analysis, core analysis and theoretical calculations. The results show that the strength of high-strength mortar can reach 105.6 MPa, thus the high-strength mortarcan be used to simulate the rocks above medium strength. Under explosion damage, the simulated rock medium is divided into four zones including crush zone, compression zone, crack zone and elastic zone. Each damage zone's range is related to the radius of the borehole and the column of explosive. Theradius of crush zone, compression zone and crack zone respectively are about 2.2, 5.2 and 32 times than the diameter of borehole. The results of the three methods are comparable. This experiment can truly show the drilling explosion damage of simulated rock medium by high-strength mortar.
  • Reinforcing Test Study on Damage Unreinforced Composite Lining of Subway Bored Tunnel
    Li Yujie, Xu Huijie, Wang Mengshu, Song Guoxia
    Chinese Journal of Underground Space and Engineering. 2018, 14(6): 1512-1518.
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    Taking composite lining diseases of a Beijing subway line as research background, indoor model test method was used to studying lining structure damage rule and reinforcing effect. Through experiment, it was concluded the main conclusions as follows: (1) the crack propagation of test beam could be divided into four stages by test load demarcation point, which were 90 kN, 120 kN, 180 kN and 350 kN. (2) The damage test of aramid fiber cloth on reinforcing test beam showed that, the aramid fiber cloth paste on test beam bottom has improved the test beam bending performance, and the deflection increased from 13 cm to 18 cm. When the test beam damaged, the two side of 3 m long aramid fiber cloth always pasted on beam bottom, and never appeared chip off-falling and fiber cloth fracture damage forms, which was a common phenomenon on straight beam test. (3) Through the contrast test, when the aramid fiber cloth using different injured test beam, the yield load of test beams could increase by 17% ~ 39%, the ultimate load of test beams could increase by 46%～71%, all the bearing capacity of test beams were obviously increased. The research conclusions have important theoretical guiding significance for the comprehensive treatment work on the tunnel lining structure cracks during the next phase.
  • Experimental Study on the Relationship of Gateway Surrounding Rock Stability and Pillar Size Layout
    Xin Yajun, Li Mengyuan, An Dingchao, Pu Qingwei, Hao Haichun
    Chinese Journal of Underground Space and Engineering. 2018, 14(6): 1519-1526.
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    Coal pillar size can affect the stability of gateway surrounding rock. Based on similar simulation experiment of surrounding rock deformation and stress distribution in weaken-coal gateway with different pillar size, the paper studied the evolution of surrounding rock cracks and strata movement, analyzed stress distribution of surrounding rock and supports with different pillar size, and determined the pillar size of the initial disturbance in gateway surrounding rock and the critical instability. The results showed that, the crack extension of level weaken-coal surrounding rock was roof crack initial following two-side horizontal extension, whose induce points were in two sides near to two roof angles. When coal pillar was less than 300 mm, roof cracks extended seriously following two-side asymmetric plastic damage, roof subsidence, two-side convergence, surrounding rock stress change and support loading were severe, the peak stress-concentration coefficients of surrounding rock and support were 2.53 and 1.67 respectively. When pillar was 150 mm, cracks in two pillar sides were connected with ones in coal wall of mine area, the pillar showed yield bearing, loading on right gateway support was more than on left one, and the surrounding rock stability decreased. The pillar size affecting surrounding rock stability was 300 mm, minimum pillar guaranteeing surrounding rock stability was 150 mm.
  • Experimental Study on Negative Friction Resistance of Pile in Frozen Soil under Raising Atmospheric Temperature
    Tang Liyun, Wang Xin, Yang Gengshe, Jin Long, Wang Xiaogang
    Chinese Journal of Underground Space and Engineering. 2018, 14(6): 1527-1535.
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    The moving downward of the upper bound of frozen soil with global warming caused the increase of thaw settlement of the soil around pile, weakened the negative frictional resistance, and finally adversely affected the long-term performance of the pile in permafrost regions. To study the influence of raising atmospheric temperature on the negative frictional resistance of piles, according to the data on No. 16 pile of the Chalaping Bridge, the temperature field of soil around the pile after 10, 30, 50 and 70 years was first predicted, and the corresponding negative frictional resistance of the frozen piles in these years was also analyzed by physical model tests that were conducted on the basis of simulated temperature field. The negative frictional resistance of frozen piles was 5.2 kPa, 2.4 kPa, and 2.0 kPa after 10, 30, and 70 years respectively. It's indicated that the freezing force on the pile side decreased and the negative friction resistance of the pile increased 10 years later because of the influence of the pile and atmospheric temperature; the ground temperature decreased with the increase of the predicted period, making the freezing force increase significantly and the freezing force decrease gradually.
  • Experimental Study on Failure Mode of Ring-shaped Reinforced Retaining Wall Based on Centrifugal Test
    Liang Bo, Wang Tao, Zhao Ningyu, Li Yanjun, Ling Xuepeng
    Chinese Journal of Underground Space and Engineering. 2018, 14(6): 1536-1541.
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    There are few studies on the forms of failure of ring-shaped reinforced retaining walls. Two groups of centrifugal simulation experiments were carried out to study the failure modes and deformation characteristics of annular reinforced retaining walls. It is preliminarily determined that the shape of the rupture surface of the ring-shaped reinforced retaining wall is similar to that of the "0.3H" rupture surface, and it is a broken line shape. Comparative analysis of the monitoring points near the rupture surface of the retaining wall has shown that the annular reinforcement form has a good limit to the development of the rupture surface of the retaining wall, and it can make the lateral displacement of the wall change more evenly. The ability of the annular reinforcement form in limiting lateral deformation of the retaining wall is greater than that of vertical deformation.
  • Model Test on the Bending Stiffness of Metro Shield Segment Joint and Its Numerical Analysis
    Yang Zhao, Luo Huiwu
    Chinese Journal of Underground Space and Engineering. 2018, 14(6): 1542-1548.
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    The model test was carried out to research the bending stiffness of longitudinal segment joint. The following conclusions are obtained: (1) the curve of the bending stiffness of segment joint is a highly nonlinear and non- monotonic functions whose slope is difficult to be expressed. (2) The bigger the bending moment of the longitudinal segment joint, the smaller the bending stiffness. The absolute values of positive bending stiffness are significantly larger than those of negative ones. The bending stiffness increases firstly and then decreases when axial force increases under the condition that the eccentricity remains unchanged. (3) The curve of the bending stiffness can be simplified as a straight line which passes through the original point when the bending stiffness is less than inflection points (150 ). But when it is greater than inflection points (150 ), the curve shows a significant turn point and the curvature of the curve increases. The bending stiffness obtained from the numerical simulation is consistent with that of the model test, but the former is 10%~20% larger than that of the later. Comparing the numerical simulation results and experimental data, it shows that the results of the model test are reliable, and the method and the constitutive relationship in the numerical simulation are feasible.
  • Experimental and Numerical Analysis on the Rockfall Attenuating Net of the Underground Engineering Gateway
    Cui Lianming, Shi Shaoqing, Wang Wenkang
    Chinese Journal of Underground Space and Engineering. 2018, 14(6): 1549-1557.
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    The gateway of underground engineering is often threatened by the collapse and rockfall disaster. Generally, the rockfall protection net can be used. The rockfall attenuating net is a new type of rockfall net. The "attenuating, controlling, and flexible protecting" structural form can reduce the internal force peak efficiently, thus reduce the cost of construction and maintenance. In order to explore the deformation mode of the net and the load transfer law of the system under the impact of rockfall, a model test was conducted to study the protective performance of the new rockfall attenuating net. It is found that the rock overflew directly to the bottom of the test slope without the rockfall attenuating net. After the layout, the altitude of rockfall was significantly reduced and the purpose of controlling the trajectory of rockfall was achieved. According to the model test, a numerical model was built in finite element method and verified in aspects of the deformation of the net, the trajectory of the rockfall and the exit speed of the rockfall. Based on that, further study on the energy dissipation mechanism and load transfer mechanism can be conducted.
  • Simulation and Experimental Research on Cutting Efficiency of the Impregnated Teeth
    Lin Min, Li Weijun, Song Dongdong, Ren Haitao, Zuo Long
    Chinese Journal of Underground Space and Engineering. 2018, 14(6): 1558-1563.
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    PDC bit and Cone bit usually performance with low efficiency, rapid wear and short service life in the deep hard stratum. By the contrast, impregnated diamond bit owns good drilling properties relying on its special rock breaking mechanism and self-sharpening and has become one of the important means to improve the rock breaking efficiency in this formation. The influence law of diamond concentration, particle size, drilling pressure, rotational speed on the cutting efficiency of impregnated tooth was researched by impregnated tooth grinding experiment. The physical model of the impregnated grinding was established and its cutting process was simulated numerically by PFC3D. The results of experiment and discrete element simulation show that the parallel bonding model using impregnated grinding sand is feasible. The effect of particle size, drilling pressure, rotational speed, concentration on the cutting efficiency of impregnated teeth decreases gradually. The original experimental data were obtained for the analysis on behavior, individualization design, strata adaptability evaluation of the impregnated bit and the bit selection by the experiment research on cutting performance of the impregnated teeth
  • Research on Macro-Meso Mechanical Properties of Sandy Cobble Surrounding Rock with Different Moisture Content
    Lu Junfu, Zhang Cunwei, Zhong Yingzhe, Liu Dagang
    Chinese Journal of Underground Space and Engineering. 2018, 14(6): 1564-1570.
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    Moisture content has a great influence on the stability of surrounding rock of tunnel with granular material. Using both three axis test and particle discrete element numerical three axis test with different moisture content, research on macro mechanic and micromechanics properties of different content of coarse sandy pebble surrounding rock under three kinds of confining pressure, including 100 kPa, 200 kPa, 300 kPa were conducted. The influence of moisture content on the macro microscopic mechanics parameter properties of pebble tunnel surrounding rock were analyzed. The results show that: with the increase of the moisture content, the peak stress of the surrounding rock, internal friction angle and cohesive force decrease; When sandy cobble of surrounding rock deformation and failure, the axial strain is about 4%. After the stress peak value, the sandy cobble of surrounding rock can still bear larger stress. Mesoscopic parameters such as contact modulus, friction coefficient, particle stiffness ratio porosity and the normal contact strength of different coarse contents sandy pebble were determined. Research results provide a theoretical basis for discrete element fine simulation of sandy cobble stratum tunnel surrounding rock stability.
  • Size Effect Study of Red Soft Rock Based on Grey Relating Analysis Theory
    Lü Longlong, Song Li, Liao Hongjian, Li Hangzhou, Zhang Tianyu
    Chinese Journal of Underground Space and Engineering. 2018, 14(6): 1571-1576.
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    To investigate the size effect relationship between rock mass and small size sample on strength of red bed soft rock, a series of uniaxial compression tests of the red bed soft rock from Dingxi with different ratio of height to diameter were done. Elastic modulus, Poisson ratio and deformation modulus of soft rock are all uncertain values due to its complicated mechanical properties. The grey correlation analysis theory was introduced and four grey correlation analysis models were compared. Research results showed that grey correlation incidence model is more suitable for the red bed soft rock. By calculating correlation incidence degree of the sample’s height diameter ratio, elastic modulus, deformation modulus, Poisson ratio on strength, the analysis results show that when the height diameter ratio is greater than or equals to 1.2, the effect of Poisson ratio on strength is largest and the height diameter ratio is second, when the height diameter ratio is less than 1.2, the effect of height diameter ratio on strength is the largest, the Poisson ratio is second and the effect of deformation modulus on strength is greater than elastic modulus. Thus, research on size effect of the red bed soft rock needs to consider the joint effect of height diameter ratio, Poisson ratio and deformation modulus. By defining the size effect coefficient and deformation modulus megapascal image, the four-dimensional equation of size effect is fitted by using the method of simplifying dimension. The simulation results show good agreement with the test results.
  • Study on the Measurement and Prediction of Thermal Properties for Sand
    Zhen Zuolin, Zhu Jianghong, Zhang Huyuan, Ma Guoliang, Gai Yuxi
    Chinese Journal of Underground Space and Engineering. 2018, 14(6): 1577-1586.
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    Thermal properties of sand stratum are important reference index for the design of HVAC in the development and construction of underground space. Thermal properties of sand specimens were measured by Hot Disk TPS2500s Thermal Constants Analyzer. Effects of dry density and moisture content on the thermal properties of sand were investigated and theoretical predictions of thermal conductivity were analyzed. Test results showed that for the same dry density, the thermal conductivities and volumetric heat capacities of remolded sand increase with moisture contents increasing. When the moisture content is low, the thermal diffusivities of remolded sand increase with moisture contents increasing, while the thermal diffusivities of remolded sand tend to be stabilized or decrease with moisture content increasing after a certain moisture content is reached. When moisture contents are the same, the thermal conductivities, the volume specific heat capacities and the thermal diffusivities of remolded sand increase with the increase of dry densities. The variation trend of thermal physical parameters of remolded sand and undisturbed sand with moisture content are roughly the same, while it is more obvious for undisturbed sand. The feasibility of predictive theory are discussed, Cote and Konrad model predicts thermal conductivities of remolded sand more effectively
  • Modeling of Cracking Processes and Size Effects of Three-point Bending Beams Using a Continuum-discontinuum Method
    Wang Xuebin, Guo Xiang, Lu Weinan, Zhu Mingze
    Chinese Journal of Underground Space and Engineering. 2018, 14(6): 1587-1593.
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    The self-developed continuum-discontinuum method, which is applicable for modeling a series of complex mechanical behaviors, such as deformation, cracking, contact, friction and rotation of quasi-brittle materials (such as rocks and concretes), introduces the Lagrange element method, the discrete element method and the fictitious crack model. Cracking processes and size effects of three-point bending beams are modeled under displacement-controlled loading, in which a few nodes permitted to separate are prescribed at the middle spans of beams. It is found that as deformation proceeds, nodes at the middle span of the beam continuously separate, cracks continuously extend, and the maximum principal stresses always concentrate at the tip of the crack. With an opening of the crack, unloading occurs at two sides of the crack. For the beam with larger span-depth ratio, the load-carrying capacity is lower, and less steep pre-peak and post-peak load-displacement curves can be expected. For the thick beam, the stored elastic strain energy is high; cracking is fast at a short time. This finding can explain the phenomenon that rockbursts can be induced by the cracking and movement of super-thick conglomerate strata overlying working faces in coal mines
  • Study of Foundation Soil Bearing Capacity Design Based on Robustness
    Zhang Feng, Zhou Feng, Wang Yao, Chen Cheng, Li Qiao
    Chinese Journal of Underground Space and Engineering. 2018, 14(6): 1594-1602.
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    The determination of foundation soil bearing capacity is very important for geotechnical engineering design. Only the bearing capacity of foundation soil is taken into account, and the safety level and stability level of design are neglected. Aiming at the influence of the uncertainty of soil parameters on the bearing capacity of foundation soil and the different calculation methods, a new design based on robustness was present. Firstly, the mean and standard deviation of the soil parameters were investigated to clarify the uncertainty of soil parameters in robust geotechnical design (RGD) method. Secondly, the sizes of the foundation were taken into consideration as design parameter, and the bearing capacity of foundation soil was designed by using the limit state equation of bearing capacity as the objective function. With the RGD approach, the cost-efficiency and robustness were the optimize target to achieve the multi-objective engineering optimization. The design scheme satisfies the bearing capacity. Meanwhile, the cost-efficiency and robustness of the design were guaranteed. A comparative analysis was made of the design on the basis of the traditional methodology and the RGD methodology, and the significance of the proposed RGD methodology.
  • Optimization Study on Jacking Force of the Tunnel Face when Shield Tunnel Crossing the Upper-soft and Lower-hard Stratum
    He Xiangfan, Gao Feng, Shen Xingzhu, Wang Fan
    Chinese Journal of Underground Space and Engineering. 2018, 14(6): 1603-1610.
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    The upper-soft lower-hard composite stratum is a kind of special geological conditions frequently encountered in shield construction, but there are many difficulties in shield construction under such stratum conditions. Based on the shield tunnel engineering crossing the upper-soft lower-hard stratum in Shenzhen Metro Line 7 Project, numerical simulation method is used to optimize different jacking force schemes of each partition in tunnel face when tunnel crossing the upper-soft lower-hard composite stratum (stratum crossed by tunnel “from the soft into hard” and “from the hard into soft”). The calculation results indicate that measures of properly decreasing the jacks’ thrust of upper partition and increasing the jacks’ thrust of lower partition in the tunnel face could effectively reduce the stress of segments in the stratum crossed by tunnel “from the soft into hard” (S1 decreases 2.76~3.1%, S3 decreases 3.39~3.46%), and it also suggests that proportion of jacks’ thrust of the upper, middle and lower parts in tunnel face within the range 8∶13∶18~10∶13∶16 is reasonable. However, such adjustment measures of shield posturer will make the ground subsidence show an increase tendency, so we can also increase the soil pressure properly to restrain the increase tendency of ground subsidence in the actual project.
  • Location Optimization of Long Tunnel Exploration Based on the Markov Method and Information Entropy
    Xu Chen, Hu Chengke, Liu Xiaoli, Wang Sijing, Zhu Yujie
    Chinese Journal of Underground Space and Engineering. 2018, 14(6): 1611-1617.
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    Based on Markov method and basic theory of information entropy, this paper put forward a new method to optimize exploration sites location to get more information by limited geological exploration. According to the existing exploration sites data, using the theory of Markov method, classification of tunnel geological lithology were performed and various lithology distribution along the tunnel were determined. Based on the information entropy theory, the distribution of information entropy values along the axis of the tunnel was obtained. Larger information entropy means larger uncertainty and vice versa. Among the maximum information entropy calculated corresponding to the geology situation with newly added different exploration sites location, the minimum one is chosen to be with minimum uncertainty and the corresponding geological exploration sites distribution is determined to be the optimal one. Taking the Bashiyi Daban water diversion tunnelling engineering in Xinjiang as a case, the maximum information entropy of the geology condition with 23 newly added geology exploration sites along the 30km tunnel axes were analyzed by the above method. The results proved the validity of the present method. The method and results in this paper may be used not only to predict the geology condition of underground engineering based on the exploration geological information, but also to optimize the geology exploration sites distribution.
  • Model Experiment on the Impact of Filling Sand Construction Sequence on Immersed Tunnel Foundation
    Wan Chao, Zhou Enxian, Wu Gang, Shen Yongfang, Lü Zhenliang
    Chinese Journal of Underground Space and Engineering. 2018, 14(6): 1618-1624.
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    Filling sand method is one of the main construction method of foundation treatment in immersed tunnel engineering. In order to solve the problem of filling sand construction sequence, based on the real-time observation of filling sand in the equivalence ratio model test, the influence of filling sand construction sequence on the bottom pressure and the diffusion of sand deposit was discussed. Research shows that filling sand construction sequence has a corresponding influence on foundation treatment. Early stage filling sand construction influences the late stage filling sand construction in a particular direction. Because of the early filling sand construction, the time of late stage filling sand construction is greatly reduced. Late stage filling sand will lead to the floor pressure increase in the completed filling sand area.
  • Calculation of Bearing Capacity of New Type Concrete-discrete Material Tandem Compound Pile
    Guo Youlin, Zhao Minghua, Fu Guihai, Yu Pengfei
    Chinese Journal of Underground Space and Engineering. 2018, 14(6): 1625-1633.
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    It is easy for the crushed stone pile to destroy within the height range of 1 ~ 3 times of the height of pile diameter. A new type of composite foundation with gravel pile composite foundation, concrete-gravel bulk material series-coupled pile composite foundation was proposed, and the construction technology of the new composite foundation was explained. Based on the Meyerhof method in calculating the deep foundation bearing capacity, a multi-slide failure model was used to calculate the deep-layer bulging failure of the composite pile of concrete-gravel bulk material. The critical slip surface was found by stochastic optimization algorithm, and the ultimate bearing capacity of single pile was calculated. The calculated results of the bearing capacity of the new composite pile were compared with the results of the numerical simulation and the bearing capacity of the traditional gravel pile. The results show: the accuracy of the proposed multi-slide analytical method is better. The bearing capacity of the new pile is obviously higher than that of the conventional gravel pile. When the concrete pile length is 1 m, the bearing capacity of new type pile is increased 32.76%. When the concrete pile length is 2 m, the bearing capacity of new type pile is increased 54.74%.
  • Analysis on Rational Spacing between Adjacent Anti-slide Piles Based on Interaction Effect of Soil Arches
    Wang Peiyong, Dong Tong, Li Xiudi
    Chinese Journal of Underground Space and Engineering. 2018, 14(6): 1634-1638.
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    Spacing between adjacent piles, one of the important parameters of anti-slide pile design, is ascertained by analyzing soil arching effect. However, because of incomplete cognition of internal force characteristics and interaction effect in soil arch, the most dangerous section, dominative condition and spacing between adjacent piles are obtained inaccurately. Based on the analysis of the coupling mechanism of the adjacent soil arch, stress state of the triangular compressive region was obtained by material mechanic. Then, taking the strength of the triangular compressive region as the control condition, the reasonable value of the pile spacing was discussed with the lower limit given by Mohr-coulomb theory and the upper limit determined by the vanishmen of soil arching circlet. Finally, the calculation procedure of spacing between adjacent piles was proved to be rational by a practical project. The expressions of spacing between adjacent piles is able to reflect the influences of soil and anti-slide pile practically, which provide application for anti-slide piles engineering
  • Effects of Soft Soil Layer on the Ground Settlement of a Long-narrow Deep Excavated Foundation Pit for Subway Station
    Zhang Yanshu, Xue Xuchao, Zhuang Haiyang, Liu Xuezhu
    Chinese Journal of Underground Space and Engineering. 2018, 14(6): 1639-1651.
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    With the rapid development of the rail transit in China, the number of long and narrow deep foundation pits for the subway stations are increasing fast. Particularly the long-narrow deep foundation pits along the Middle-lower Yangtze River and the coastal line are mostly excavated in the deep soft soil layer, which has caused a serious threat to the safety of the deep excavated foundation pits. Accordingly, by using the Midas software, a three-dimensional finite element model was established to simulate the soil and retaining structure interaction system. Firstly, by comparing the on-site measured results with the numerical modelling, the accuracy of the numerical calculation model was verified. Then, by the 108 calculation conditions, the effect of the soft soil thickness and buried depth were analyzed to the ground surface settlement of the long-narrow deep foundation pit. The results show that when the soft soil layer is mainly located in the lateral foundation above the pit bottom, the changes of the soft soil thickness have great influence on the around ground surface settlement of the foundation pit. When increasing the soft soil buried depth the ground surface settlement of the foundation pit is first increasing and then decreasing. As a result, the turning point for the above change law is located in a certain range above the bottom of the foundation pit. When the depth of soft soil layer is larger and thicker enough, the excavation depth has a greater impact on the around ground surface subsidence. What’s more, the effect of the excavation depth is more obvious when it is larger enough. At the same time, according to the numerical modelling, the statistical relationships among the thickness, the depth of the soft soil layer and the surface settlement, is also given
  • Analysis of Tunneling Stability Using Classic and Extended Drucker-Prager Model
    Zhang Xin, Song Hongwei, Yan Xiao
    Chinese Journal of Underground Space and Engineering. 2018, 14(6): 1652-1657.
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    The classic Drucker-Prager model is a popular model in numerical simulations of tunneling engineering. With progress of theory and method, many finite element software have researched and developed an Extended Drucker-Prager mode in order to cover its original shortage. According to the problem that parameters of EDP model are special, this paper studies extended Drucker-Prager model carefully in ANSYS. By comparing their different yield functions, the relation and physical mean of their input parameters were described and the parameter transfer formulas between DP model and EDP mode were given. Then under plain strain condition, a deep circular tunnel engineering stability was analyzed by an analytic stress solution and a finite element method using DP and EDP model separately. Therefore, some conclusions are drawn. Firstly, as an improvement, because of considering effect of hardening mode of material, the EDP model is more reasonable and conform the case further. Secondly, parameters value of EDP model, such as pressure sensitive parameter and yield stress of material, can be calculated from cohesion and friction angle. Thirdly, in elasto-plastic analysis for deep circular tunnel, 3 stress distributions which are analyzed by an analytic stress solution and a finite element method using DP and EDP model separately are mostly agree. However, the radius of plastic zone with an analytic stress solution is smaller than one with finite element numerical method.
  • The Distribution Form of Disturbed Stress Field in Coal Floor    under Deep Mining Exploitation
    Li Jiazhuo, Li Chuanlei, Li Yang, Yuan Anying, Liu Wanrong
    Chinese Journal of Underground Space and Engineering. 2018, 14(6): 1658-1666.
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    Variation characteristics and spatial distribution of mechanical field after coal mined were studied by comprehensive research methods. The results show that: in mining initial stage, the maximum principal stress approximately equals to the vertical stress ahead of coal wall and near the open-off cut, and it spreads to coal floor likely bulb. High shear stress spreads to coal floor of two sides of stope, and decays rapidly. Horizontal stress is not high concentration. With mining continuing, the maximum principal stress begins to deflect, then maximum principal stress arch appears in coal floor stratum. The peak value of vertical stress along the depth declines follows proximately negative exponential law. The shape of high vertical stress area resembles ear-shape. The rock stress decreases in the goaf with delays. Vertical stress finally tends to be flat base, and pressure releasing range present 'eight' form. Coal floor stress has the characteristics of successive. Decay rate of vertical stress in coal floor stratum is faster than the roof rock breaks. Additional horizontal stress and shear stress severely concentrates and subsequently decline dramatically. The stress of floor heave comes from tensile stress, swelling stress and bearing stress. Coal floor in the front of coal wall has perturbation, and crack will initiate in advance
  • Seismic Safety Analysis and Evaluation of Yeba Beach High Arch Dam
    Chen Lin, Pan Yanfang, Liu Xiaoqiang
    Chinese Journal of Underground Space and Engineering. 2018, 14(6): 1667-1675.
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    Yeba Beach high arch dam is the first high dam hydropower project approved by China Renewable Energy Engineering Institute after “Code for Seismic Design of Hydraulic Structures for Hydropower Projects” (NB 35047-2015) formally promulgated and implemented on September 1, 2015. The new code was changed and revision in many aspects, including seismic input, material parameters, seismic grade, evaluation methods and others. This paper introduces the results of the dynamic analysis, seismic safety evaluation and measures taken by the Yeba Beach arch dam in accordance with the new code. According to the comprehensive analysis of the results, it shows that the base constraint area, dam heel, middle part of downstream face and the right and left bank dam abutment resisting force body is key parts of arch dam earthquake resistance, and Yeba beach arch dam is safe and reliable under design earthquake, it also can keep steady under maximum credible earthquake
  • The Activity Trend and Risk Assessment of Land Subsidence along Metro Lines in Xi’an City
    Wang Zhen, Huang Qiangbing, Sun Xiaohan, Zhang Ning, Yang Chengsheng
    Chinese Journal of Underground Space and Engineering. 2018, 14(6): 1676-1683.
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    Land subsidence is one of the most typical urban geological hazards in Xi’an, China, which seriously restricts the development and utilization of Xi’an urban underground space, especially severely hinders the development of urban rail traffic. The uneven stratum settlement often induces the longitudinal cracking failure of metro tunnel lining structure and leakage and other metro diseases, which brings potential safety hazard to Xi’an metro construction and operation. Therefore, based on the field monitoring data of 120 land subsidence monitoring points from 2007 to 2012, the method of equal velocity extrapolation was proposed to predict the trend of the land subsidence along the metro lines and the largest settlement value was predicted with the method of the unit deformation. It is concluded that the maximum subsidence of Hujia temple land subsidence center is up to 1960mm, the maximum subsidence of Xiaozhai, Great Wild Goose Pagoda, the Xi Gongda land subsidence center is about 400~700 mm, and the maximum subsidence of Xijia temple, Hanyuan temple land subsidence center is about 200~300 mm. The regional land subsidence geohazard along the metro lines was evaluated according to the characteristics and importance of the metro engineering. The results show that the influence of regional land subsidence on metro lines is mainly concentrated in the range of land subsidence center, and the risk of the southern section of metro lines significantly greater than the middle and northern sections. The above results can provide an important reference for Xi’an metro construction and safe operation
  • Risk Assessment during Construction of High-level Radioactive Waste Geological Disposal Underground Laboratory
    Zhang Qiangyong, Zheng Yang, Wu Dong, Li Xingjun, Zhang Zhihao
    Chinese Journal of Underground Space and Engineering. 2018, 14(6): 1684-1691.
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    High level radioactive waste (HLW) geological disposal underground laboratory plays a vital role in geological disposal as an underground research facility used for developing and validating the HLW geological disposal technology, evaluating suitability of the site. In order to ensure the construction safety of underground laboratory, it has very important theoretical significance and engineering application value to analyze and evaluate the construction risk. Fault tree analysis (FTA) and analytic hierarchy process (AHP) are important method in engineering risk assessment. This paper combined FTA structure importance with the weight of AHP, first identified the construction risk factors of underground laboratory, built up the fault tree model, then introduce the calculation result of FTA structure importance into the judgment matrix of AHP, and finally put forward AHP method based on FTA. This method is applied to evaluate the construction risk of China's first HLW disposal underground laboratory in Beishan, Gansu province, also obtained rose cloud for the distribution of risk weight of underground laboratory, and put forward the suggestions and conclusions to ensure the safety of underground laboratory construction
  • The Optimization Method for Natural Ventilation and Daylighting of the Sunken Architecture
    Zhai Yingni, Wang Yi, Huang Yanqiu, Xiao Yongqiang
    Chinese Journal of Underground Space and Engineering. 2018, 14(6): 1692-1700.
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    The sunken architecture can raise the land-use capability without the defects of poor natural ventilation and inadequate daylighting of conventional underground buildings. So it has great development significance and application value. An optimization method based on orthogonal experiment was proposed for the ventilation and daylighting of the sunken architecture. The average indoor pressure differential and daylight factor of the sunken architecture were calculated by numerical simulation. The impact order and rule of the architecture design factors (the sunken height, the sunken width, the windowsill height and the number of floors) on the natural ventilation and daylighting of the sunken architecture were analyzed based on orthogonal experiment. The optimized combination values of the architecture design factors were obtained with good natural ventilation and sufficient daylighting. The method can provide easy and effective way for the schematic design of the sunken architecture.
  • Development of Large Scale Experimental Technique and System for Underwater Tunnel
    Wu Mengjun, Li Ke
    Chinese Journal of Underground Space and Engineering. 2018, 14(6): 1701-1708.
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    Aiming at the current situation of the increasing number of underwater tunnel construction and the increasing difficulty of technology in China, based on extensive research of literature, experimental pool and related experimental research, the functional requirements of the underwater tunnel experimental research system were put forward, the research and design of the underwater tunnel experiment technology and system were carried out. Using the experimental system, model experiment for immersed tube, shield, drilling and blasting, submerged floating tunnel, etc. all can be carried out. It fills the insufficient that domestic pool can only use for immersed tube, submerged floating tunnel model experiment, which can provide technical support and service to solve the major and difficult underwater tunnel construction and the main technical bottlenecks in the industry
  • Analysis on Environmental Impact of Shield Tunnel Operation on Water-rich Pebble Stratum
    Yang Wenbo, Li Lingui, Dai Zhiren, Xu Zhaoyang
    Chinese Journal of Underground Space and Engineering. 2018, 14(6): 1709-1716.
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    According to the characteristics of the uneven distribution of particles and high content of pebbles in water-rich pebble stratum, FLAC3D was used to analyze the vertical dynamic response characteristics of the surface and buildings under the vibration load of the train, which took a subway tunnel project in Chengdu as the background. The results show that with the increase of the horizontal distance from the orbit, the vertical dynamic response of the surface is weakened. The attenuation is slow when measuring points are near to the tunnel, and the attenuation is obvious when farther to the tunnel. Generally speaking, the dynamic response of the building amplifies slowly with the increase of storey numbers. With the increase of the horizontal distance, the dynamic response at the same floor has a significant attenuation, and the greater the distance is, the greater the attenuation is. The dynamic response of the surface and the building is concentrated in the 0~12 Hz and 20~25 Hz frequency band, which is low frequency vibration. The results can provide a reference for further improving the urban vibration control standard
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