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Quick Search     Advanced Search MODERN TUNNELLING TECHNOLOGY   2021 Vol.58 Issue.4 Published 2021-08-25 1 Research on the Impact Zoning and Construction Countermeasures for Bilateral Adjacent Tunnels with Shallow Depth and Unsymmetrical Load WANG Zhijie1 LI Jinyi1 JIANG Xinzheng1 LI Zhen1 ZENG Qing2 WANG Ning2 The construction of new tunnels can cause a redistribution of stresses in the surrounding rocks, which may pose a great impact on the adjacent existing tunnels. Based on the new Wudiao No.1 tunnel and Wudiao tunnel on the Pucheng-Meizhou railway, which approaches both the right and left sides of the existing Wudiao tunnel on the Xiangtang-Putian railway, this paper conducts a theoretical research, establishes an expression suitable for the impact degree on existing tunnel caused by construction of bilateral adjacent tunnels, and obtains two types of adjacent impact zoning based on the structural displacement criterion and the structural reliability criterion. By means of numerical simulation and regression calculation, two types of bilateral adjacent impact zoning are determined. And the results show that, compared to the adjacent impact zoning based on the structural reliability criterion, the adjacent impact zoning method based on the structural displacement criterion has a smaller range of strong impact zone and a larger range of weak impact zone. Corresponding construction countermeasures for the existing tunnel, new tunnels and intermediate soil pillars in different impact zones are put forward. Structural displacements and lining stresses in existing tunnel are monitored within the different impact zones. And the monitoring results show that when the suggested construction countermeasures are taken, the structural displacements and lining stresses in the existing tunnel could be well controlled, which is more affected by the new unsymmetrical loading tunnel on the left than by the new tunnel on the right. 2021 Vol. 58 (4): 1-11 [Abstract] ( 1939 ) [HTML 1KB] [ PDF 4792KB] ( 2522 ) 12 Study on Factors Affecting the Stability of Double-Layer Superimposed Lining#br# in Deep-Buried Tunnels under the Action of High Water Pressure #br# WANG Wenjuan GAO Xin With the gradual increase in awareness of ecological resources protection, the waterproofing type of tun? nels under high water pressure has also been gradually shifting from the "mainly draining" to "fully waterproofing",so resulting in difficulties in mass concrete construction. In view of this, the "double-layer superimposed lining" solution is proposed to reduce the thickness of the structure by "splitting", which can effectively mitigate harmful deformations caused by the cement hydration heat in the structure, and enhance the implementability and operability of mass concrete structure construction, while also improve the quality and effectiveness of tunnel waterproofing.Taking the sea-crossing tunnel section of the Qingdao Metro Line 1 as the engineering background, this paper conducts research of the factors affecting the stability of double-layer superimposed lining by the finite element analysis software ANSYS, and the conclusions are drawn as follows: 1) due to the waterproofing layer between linings, only the radial compression stiffness of the spring can be considered in terms of contact mechanics behaviors of the lining bonding surface, while ignoring the impact of tangential shear stiffness of the spring; 2) when the radial spring stiffness of the bonding surface is of equal order of magnitude to the elastic modulus of the structure at both sides, the safety coefficient curve basically tends to converge, and the structural failure sequences are in the order of the inner lining inverted arch, inner lining arch foot, outer lining inverted arch, outer lining arch foot, inner lining arch vault,outer lining arch vault; 3) the higher the subgrade reaction coefficient of the surrounding rock is, the greater the safety coefficient of the superimposed structure will be, and so attention should be paid to improving the subgrade reaction coefficient of poor surrounding rocks and maintaining that of good surrounding rocks during the design and construction process; 4) the safety coefficient of the superimposed structure increases with the increase of the stiffness of each lining layer, and the inner lining structure has the effect of increasing and improving the safety of the outer lining structure. 2021 Vol. 58 (4): 12-20 [Abstract] ( 632 ) [HTML 1KB] [ PDF 3475KB] ( 803 ) 21 Research on the Calculation Method for Frost-Resistance Fortification Lengths of Tunnels in Cold Regions U Li1,2 SUN Yuan1,2 WANG Mingnian1,2 At present the design of frost-resistance fortification lengths of tunnels in cold regions mainly relies on engineering analogies and requires the known temperature field inside the tunnel. In order to clarify the design criteria for the fortification length and to solve the problem of no actual temperature data in the tunnel, the critical temperatures in the tunnel are proposed under two preconditions of no freezing in the drainage pipe of the lining layer and no frost heave in the surrounding rocks, based on the theoretical solutions to temperature fields of tunnels in cold regions, as well as the investigation data analysis and numerical analysis of the temperature fields in tunnel surrounding rocks; the influence of tunnel ventilation and surrounding rock conditions on the temperature field in the tunnel is analyzed and a regression formula for calculating the temperature in the tunnel is obtained depending on the inlet wind temperature, section dimension, wind velocity and initial rock temperature; furthermore, a method for calculating the frost-resistance fortification length of tunnels in cold regions is put forward. Taking the Shahukou Tunnel as an example and using the calculated frost-resistance fortification length of the tunnel, the effects of wind temperature and tunnel section size on the frost-resistance fortification length are analyzed. The results show that the fortification length gradually increases as the inlet wind temperature decreases, the inlet wind velocity increases and the section size increases, and gradually decreases as the temperature of the surrounding rock increases, respectively. 2021 Vol. 58 (4): 21-28 [Abstract] ( 713 ) [HTML 1KB] [ PDF 3151KB] ( 1213 ) 29 Automatic Identification of Rock Structure at Tunnel Working Face Based on Deep Learning QIN Shangyou1 CHEN Jiayao2 ZHANG Dongming2 YANG Tongjun1 HUANG Hongwei2 ZHAO Shuai2 The rapid and accurate acquisition of the apparent rock structure characteristics of tunnel working faces during the construction stage from images of the tunnel face is of great significance for the understanding of the stability of the surrounding rocks to be excavated and for the decision-making during the follow-up construction stage.This paper uses self-developed digital photographic equipment to acquire 42,100 image samples from more than 150 working faces of 13 tunnels on the Mengzi-Pingbian Highway in Yunnan under different working conditions,temperatures and humidity, illuminations and dust concentrations, selects 5 main structural categories, such as blocky, layered, fractured, granular and mosaic structures, that appear in the field data set, and develops the Tensorflow-GPU-based convolutional neural network Inception-ResNet-v2 model for tunnel face rock structures with the loss rate, precision rate and recall rate of training and testing as the main evaluation indicators. Through model training it achieves automatic identification and classification of rock structure categories. The study shows that: (1) using the tunnel face images in the training and testing sets to classify the rock categories in the model, it could achieve a precision of 98.21% and 94.61% in the training and testing sets respectively, and a recall rate of 96.14%;(2) the visualization results of the testing show that the present framework has better robustness for complex site conditions, while the phenomenon of partial identification errors should be circumvented by further improving sample richness and texture diversity. 2021 Vol. 58 (4): 29-36 [Abstract] ( 721 ) [HTML 1KB] [ PDF 5301KB] ( 1361 ) 37 Automatic Identification Technique for Siltation and Blockage Conditions in Drainage Pipes in Limestone Areas Based on Big Data and Transfer Learning LI Pengju1 ZHENG Fangkun2 LV Jianbing3 WU Weijun3 LIU Feng3 CHEN Gongfa3 Siltation, blockage or failure of tunnel drainage pipes could endanger the stability of slopes and the traf? fic safety of the roads. At present, there is a lack of research on the classification of siltation and blockage conditions in drainage pipes. To explore the intelligent detection method of siltation and blockage conditions in drainage pipes,this paper studies a transfer learning based convolutional neural network classification algorithm for siltation and blockage targets in drainage pipes, taking the Gaofeng tunnel on Guangzhou-Lianzhou Expressway and other tunnel projects in northern Guangdong as the background. By using a model transfer method, the drainage pipe image data are input into a pre-trained convolutional neural network for training in order to classify the new images. The collected image dataset of drainage pipes is tested to compare the identification accuracy of three different network models for the dataset. The results show that the classification and identification of siltation and blockage conditions in drainage pipes by using ResNet-18 could reach a 93% accuracy and achieve the effective classification of siltation and blockage conditions in drainage pipes. Also, the identification accuracy will be further improved with the expansion of the dataset in the future. 2021 Vol. 58 (4): 37-47 [Abstract] ( 611 ) [HTML 1KB] [ PDF 6407KB] ( 1263 ) 48 Application of GPR Forward Modeling in the Identification of Tunnel Lining Defects SONG Fubin1 YANG Jie1 CHENG Lin1 LV Gao1,2 SONG Yang1 Lining defects in the hydraulic tunnels can affect the normal use of the tunnels, and thus affect the safe? ty and durability of water conservancy projects. This paper establishes a two-dimensional GPR forward model of tunnel lining based on the finite difference time domain (FDTD) method to investigate the GPR response characteristics of five types of tunnel lining defects: lining cavity shape, filling medium in the lining cavity, disengagement between the primary lining and secondary lining, uneven lining and detachment between the reinforcement and lining concrete, and summarizes the characteristics to identify each lining defect. Combined with a flood and sand discharge tunnel of a reservoir, using the obtained GPR spectrum response characteristics of different types of lining defects in the hydraulic tunnel, the multiple defects in the tunnel are identified and the lining structure and function are evaluated. The study results show that by using the FDTD method it can establish effective GPR models and provide a reliable basis for the interpretation of GPR images and the determination of lining defect types in hydraulic tunnels. 2021 Vol. 58 (4): 48-56 [Abstract] ( 649 ) [HTML 1KB] [ PDF 3913KB] ( 1008 ) 57 Safety Risk Assessment for a Subway Connecting Passage Constructed by Freezing Method ZHAI Qiang GU Weihong JIN Zhaoqin In order to assess the safety risk of a subway connecting passage constructed by freezing method, based on relevant references, existing project experience and similar project records, this paper identifies major risk factors in the four construction stages of a subway connecting passage by freezing method, establishes an evaluation indicator system, and proposes a safety risk assessment method for a subway connecting passage constructed by freezing method based on analytic hierarchy process (AHP), fuzzy comprehensive evaluation (FCE) and Bayesian network(BN). Firstly, it uses AHP to calculate the relative weights of various risk events, uses the risk-related economic loss value to describe the impact consequences of risk events, and uses BN to calculate the probability rating scores of risk events. Secondly, combining the risk-related economic loss value with probability rating score, it uses the trapezoidal membership function to calculate the membership of risk event to risk level, conducts the fuzzy comprehensive operation for the weight of risk event and the membership of risk event to risk level, and obtains the overall risk level of a connecting passage constructed by freezing method. Finally, taking Lanzhou Metro Line 1 as an example, the assessed overall risk level of the project is low risk, basically reflecting the actual situation. 2021 Vol. 58 (4): 57-66 [Abstract] ( 745 ) [HTML 1KB] [ PDF 4909KB] ( 1180 ) 67 Research Progresses on Triethanolamine Early-Strength Agents and Its Application Prospects in Tunnelling YE Fei1 HE Biao1 TIAN Chongming1 WANG Siyu1 WANG Jian1 SONG Guifeng2 This paper summaries the current research progresses on the action mechanism of triethanolamine, which is summarized into catalysis, bonding-hygroscopicity-dispersion, emulsification and solubilization. It also classifies the main components and functional properties of two types of compound admixtures derived from triethanolamine early strength agents: TEA-inorganic compound admixture and TEA-inorganic water reducer compound admixture, and provides a brief description of their action mechanisms; by comparing the research status of the two compound admixtures, this paper proposes that the development of compound admixtures should take the following features as the starting point: high efficiency, high performance, high level of environmental protection, high compatibility, and low price, etc. Finally, by comparing TEA with setting accelerator, it is found that TEA has similar functional properties to setting accelerator and that TEA and its derived compound admixtures have potential application prospects in tunnelling. 2021 Vol. 58 (4): 67-78 [Abstract] ( 607 ) [HTML 1KB] [ PDF 1738KB] ( 1114 ) 79 Research Progress on the Model Box for Shaking Table Tests XIE Jun1，2 NI Yajing2 HU Yingfei2 BAO Shuxian2 LI Yantao1 The design and fabrication of the model box is a very important aspect in the shaking table test for soilstructure interaction system, and plays a vital role in the accuracy of conclusions drawn from the simulation of the dynamic response of real soil layers and structures under seismic action. This paper summarizes and analyzes the structural forms, advantages and disadvantages of different types of model boxes used in the current shaking table model tests for soil-structure interaction, and discusses the key problems to be addressed in the design of different model boxes from three perspectives: excitation input effect, boundary effect and seismic wave input mode of the model box, as well as the improvements made by scholars so far on the basis of extant researches and in conjunction with characteristics of research projects. The paper finally analyzes the existing problems in model box research and proposes research directions in the future. 2021 Vol. 58 (4): 79-85 [Abstract] ( 630 ) [HTML 1KB] [ PDF 1824KB] ( 1209 ) 86 Study on the Characteristics and Distribution Laws of Plastic Zone Induced by Deep-buried High-geostress Hydraulic Tunnelling in Jointed Rock Mass HUI Qiang1 ZHANG Jun2 JIANG Haibo1 The deep-buried high-geostress hydraulic tunnel is located in a complicated geomechanical environ? ment, and the distribution and evolution laws of plastic zone of surrounding rock during excavation are key to controlling tunnel stability. In order to reveal the characteristics and distribution laws of plastic zone during excavation of hydraulic tunnels with high-geostress, this paper combines theoretical analysis with numerical simulation, derives a calculation formula of plastic zone range, introduces a new dimensionless parameter to evaluate the plastic zone of surrounding rock in a non-circular tunnel, and analyzes the influences of lateral pressure coefficient and excavation disturbance on the plastic zone of jointed rock mass with high geostress. The study result shows that the axial development range of rock plastic zone affected by excavation disturbance is about 1.0-1.5 times the tunnel diameter, while the influence range can be 2 times the tunnel diameter for the rock mass with joint plane. It is concluded that the lateral pressure coefficient directly affects the shape of the plastic zone of the surrounding rock, with the tendency of irregular development of the rock plastic zone along the joint plane. The greater the difference between the horizontal stress and vertical stress is, the greater the influence range of the joint plane on the plastic zone of the surrounding rock will be. In addition, the joint plane can prevent the plastic zone from development along the vertical joint plane. 2021 Vol. 58 (4): 86-94 [Abstract] ( 772 ) [HTML 1KB] [ PDF 2546KB] ( 1197 ) 95 Study on the Triaxial Compression Mechanical Properties and Damage Constitutive Model of Tunnel Sandstone in Seasonal Frozen Regions ZHANG Lili1 LANG Songjun1 DENG Lin2 ZANG Cheng3 In order to study the strength and deformation laws of surrounding rocks in seasonal frozen regions, taking highway tunnels in Liaoning as the engineering background, this paper uses the MTS815.02 triaxial test system to conduct triaxial compression tests on sandstones with different numbers of freeze-thaw cycle for studying the variation law of rock mechanical parameters with numbers of freeze-thaw cycle. And then it establishes a rock statistical damage model based on the Weibull distribution function and the D-P yield criterion, followed by model verification with the experimental data. The results show that the mechanical properties of the sandstones are significantly affected by the freeze-thaw cycle, with the peak strength, elasticity modulus decreasing and the Poisson′ s ratio increasing exponentially with the freeze-thaw cycle numbers respectively, the peak strength, elasticity modulus increasing and the Poisson′ s ratio decreasing gradually with increasing of the confining pressure respectively; the statistical damage constitutive model based on the Weibull distribution, which takes into account the freeze-thaw effect, is in good agreement with the test results, verifying the accuracy and reasonableness of the model; the Weibull distribution parameters F0 and m both decrease gradually with the freeze-thaw cycles, and their changes both have a significant effect on the model theoretical curves. 2021 Vol. 58 (4): 95-103 [Abstract] ( 663 ) [HTML 1KB] [ PDF 4070KB] ( 1087 ) 104 3D Large-scale Seismic Response Analysis of Bored Section of an Immersed Tunnel Project LI Xinxi1 YU Haitao2 LI Chunyuan3 YU Xiaodong4 XU Lei5 For an immersed tunnel project, the bored section is one of the important components, but there have not been studies on its seismic response. This paper establishes a 3D refined finite element dynamic analysis model for the bored section of an actual immersed tunnel project, in which the dynamic non-linear characteristics of soils are considered by using the equivalent linearization method, and the shear deformation of the ground is described by using remote lateral displacement boundaries as the lateral boundary conditions of the model. On this basis, a large-scale 3D response analysis of the bored section of the immersed tunnel is conducted under static and dynamic working conditions respectively to study the internal force and deformation response characteristics of each key section at the tunnel′s stiffness variation section under static and seismic effects. The results show that the seismic action has cer? tain level of influence on the internal force distribution of the structure; abrupt change would occur in the internal forces of the structure at the significant stiffness variation section; and abrupt changes in stiffness can cause a significant increase in the inter-story drifts of the structure. 2021 Vol. 58 (4): 104-108 [Abstract] ( 676 ) [HTML 1KB] [ PDF 3067KB] ( 733 ) 109 Two-Stage Safety Analysis of Overlapped Shield Tunnels Based on Dynamic Loads FENG Yi In order to study the safety of subway tunnels in water-rich sandy strata under the interaction of dynamic load during the construction and operation phases, taking the Nanjing Metro Line 5 passing under the existing Line 1 as the example, this paper establishes a numerical model of the overlapped tunnels to investigate and analyze the subway settlement and the fatigue life under the interaction of the two phases. The results show that: (1) the maximum tunnel settlement during the under-passing construction is 7.5 mm, and the design scheme of micro-disturbed grouting + full-ring steel plate in the tunnel could effectively control the tunnel deformation during this stage; (2) after operation of Line 5, the proportion of settlement at the Line 1 tunnel base in the first year is the largest, accounting for about 65% of the total settlement in the 10-year period, after which the settlement rate gradually converges;(3) through backfilling grouting in new Metro Line 5 it can significantly reduce the long-term operational settlement of Line 1, ensuring the long-term operational safety of Line 1; (4) the fatigue life of the segments at the overlap is the shortest, while the fatigue life of the segments far away from the overlap area is longer, and the overall performance of the project meets the requirements for the design service life of the structure. 2021 Vol. 58 (4): 109-116 [Abstract] ( 621 ) [HTML 1KB] [ PDF 4173KB] ( 1068 ) 117 Numerical Simulation of Construction Process and Analysis of Influencing Factors in Parallel Shield Tunnelling with Close Distance WANG Bo1 ZHENG Pengfei1 HU Jiangyang1 LIU Junyong1 LIU Shuo2 Taking the intercity rail project from Xi′an North Station to Xianyang Airport as an example, this paper analyzes the impact of the adjacent parallel construction of new tunnels on the existing tunnels through finite element software ANSYS, regarding two construction options of "left bore first before right bore" and "right bore first before left bore". It is mainly focused on the influence patterns of such factors as the ground loss rate, shield thrust and grouting during shield construction. The results show that the option of "left bore first before right bore" has less effect on the ground displacement as well as the stress and strain of the existing tunnel segments; with smaller ground loss rate; the smaller the ground settlement is, the smaller the maximum ground settlement will be, and the flatter the ground settlement slope will be; the greater the shield thrust is, the greater the ground settlement will be,and as the shield excavation distance extends, the ground settlement will gradually decrease until it tends to stabilize; the higher the elasticity modulus of the grouting materials is, the lower the amount of ground settlement will be. 2021 Vol. 58 (4): 117-124 [Abstract] ( 593 ) [HTML 1KB] [ PDF 3411KB] ( 1118 ) 125 Research on the Impact of Subway Shield Tunnelling on the Stability of Overcrossing Underpass Foundation Pit ZHANG Hong1,2 LIU Haiyang1,3 The subway shield tunnelling has a significant impact on the deformation stability and construction safe? ty of the foundation pit of the overpassing underpass. Based on the intersection project between the under-construction underpass and the under-construction Metro Line 2 in Hohhot, this paper studies the impact of subway tunnel shield tunnelling on the stability of overpassing underpass foundation pit through the comparative analysis of numerical simulation and actual measurement and monitoring data. The results show that the retaining wall of the foundation pit is affected by the under-passing construction of the subway tunnel, resulting in settlement and deformation to the inner side of the foundation pit, and the change in the axial force of the steel strut is limited, mainly in the form of settlement, with the accumulative final settlement at about 16 mm under no reinforcement condition; the soil reinforcement under the pit can significantly reduce the deformation of the foundation pit support structure, and in particular, the settlement value can be reduced to 30% of that under no reinforcement condition. The numerical analy? sis by finite element modeling can reflect the general law of the effect of the under-passing subway tunnel construction on the deformation of the foundation pit support structure, which can provide a certain theoretical basis for the design of retaining walls of foundation pits. 2021 Vol. 58 (4): 125-132 [Abstract] ( 689 ) [HTML 1KB] [ PDF 4316KB] ( 1026 ) 133 Time-Space Effect of Pile Foundation Responses Induced by Adjacent Shield Tunnel Excavation YAN Haojie ZHENG Junjie PAN Yu CHEN Pengfei In order to study the pile foundation responses during the excavation and operation periods of tunnels in soft clay soils, this paper uses the finite difference software FLAC3D to carry out a 3D fine numerical simulation of the step-by-step excavation of a shield tunnel under the CVISC model and derives the pile foundation responses varying with tunnel excavation progress and rheological time, and it comprehensively analyzes the spatial and temporal effects of the pile foundation responses induced by adjacent shield tunnel excavation and the shielding effects of the pile group under considering the rheological properties of soils. The results show that the impact of tunnel excavation on the pile foundation is mainly concentrated between one time the tunnel diameter in front of the pile foundation and 2.5 times the tunnel diameter behind the pile foundation; after the tunnel excavation is completed, the internal force and displacement of the pile foundation will continue to increase for a long time before it becomes stable,and the axial force of the pile foundation will be the first to become stable while the settlement will take the longest time to reach stability; The shielding coefficient of the internal force in the pile group is larger than that of the displacement, which will gradually increase with the increase of the rheological time. 2021 Vol. 58 (4): 133-140 [Abstract] ( 584 ) [HTML 1KB] [ PDF 3945KB] ( 1059 ) 141 The Influence of Partial Water Leakage on the Mechanical Properties of Shield Tunnels SUN Zhihui TANG Yong LIU Tao To address the problem of long-term operational safety degradation caused by water leakage in the joints of shield tunnels, this paper develops a numerical calculation model for joint leakage and analyzes the mechanical response of the segment structure with water leakage in the joints. The results show that water leakage in the joints could lead to a significant reduction in the external water pressure borne by the segments in the vicinity of the joints, and the reduction increases with the increase in the amount of leakage; the variation of internal force of the segment structure would experience three stages of rapid increase, slow increase and stabilization along with continuous leakage; a positive correlation exists between the magnitude of structural bending moments and axial forces and the amount of joint leakage; when the total leakage volume in the joints is the same, the leakage at the joints in the external tension zone has greater effect on the internal forces of the structure compared with that of leakage at the joints in the inner tension zone, and the reduction value of water pressure at the joints, when a single joint is leaking, is greater than that of multi-joint leakage; for multi-joint leakage condition, the bending moments on the leaking side of the structure under leakage condition are greater than those on the non-leaking side, showing an obvious asymmetric distribution. 2021 Vol. 58 (4): 141-149 [Abstract] ( 569 ) [HTML 1KB] [ PDF 5093KB] ( 854 ) 150 Study on the Ventilation Characteristics of High Drop and Spiral Tunnels during Operation Period ZHOU Feilong1 CHEN Quansheng1 JIA Shuaidong1 WEI Yongbing1 WU Yan2 In order to study the ventilation characteristics of tunnels with spiral structure, taking a high drop and spiral tunnel in Yunnan as the research target, this paper conducts numerical simulation and analysis of the tunnel ventilation conditions under different working conditions. The study results show that the distribution of ventilation airflow in the tunnel, as a whole, is not significantly affected by the spiral structure of the tunnel, but the longitudinal attenuation characteristics of the airflow velocity at the inner and outer sides of the tunnel are not the same within the working area of each jet fan, and a certain level of air backflow occurs. Under fire scenarios, the smoke has a smoke back-layering zone with length of around 30 m and the average airflow velocity in the tunnel is higher compared to that under normal ventilation conditions. 2021 Vol. 58 (4): 150-156 [Abstract] ( 611 ) [HTML 1KB] [ PDF 3756KB] ( 1241 ) 157 Analysis of Load Transfer of Fully Bonded Anchor Bolts under High Ground Temperature LI Fuhai1 LI Rui1 WU Haonan1 GAO Hao1 WANG Bo1 ZHANG Guibin2 CHEN Siyin3 In order to explore the influences of high ground temperature on the anchoring of fully bonded anchor bolts, this paper introduces a thermal variable equation related to material parameters of the anchoring system based on the previously derived stress distribution function of fully bonded anchor bolts, and establishes a temperature parameters inclusive mechanical model of fully bonded anchor bolts at elastic stage. Through calculation examples,this paper summarizes the change laws of mechanical properties with three different temperatures (50°C, 100°C and 150°C). In addition, it verifies the influences of temperature on the bond performance of fully bonded anchor bolts by the indoor pull-out test. The results show that: (1) as the temperature increases, the axial force at the same anchoring point of the anchor bolt increases, the maximum attenuation section of the axial force moves inwards, the peak shear stress decreases, and the peak point of the shear stress moves inwards; (2) as the temperature increases,the effective anchoring length of the anchor bolt in model 1 increases from 1.8 m to 2.8 m, the peak shear stress decreases by 21% and 34% respectively compared to that at 50 ℃, and the peak point of the shear stress moves inwards from 0.44 m to 0.79 m; (3) as the temperature increases, the peak shear stress of the fully bonded anchor bolt decreases, the load transfer length of the anchor bolt increases, and the transfer efficiency is reduced. 2021 Vol. 58 (4): 157-162 [Abstract] ( 643 ) [HTML 1KB] [ PDF 1493KB] ( 1128 ) 163 Hydraulic Fracturing Test on In-Situ Stress and Its Distribution Characteristics in an Engineering Site XU Gancheng1 YUAN Weize1 LI Chengxue1 ZHAO Shunli2 ZHU Yonghe2 In order to investigate the distribution conditions of the in-situ stress field, which is required for the construction and design of a project, this paper conducts in-situ stress tests on two boreholes in engineering Zone A and Zone B, using the hydraulic fracturing method. The test results show that: (1) the in-situ stress field in the testing zones is dominated by the squeezing in the NW-NWW, with the orientations of maximum horizontal principal stress in Zone A and Zone B being around N49°-57°W and N72°W respectively, indicating that the stress fields in these two zones are consistent, but due to certain differences in topography and tectonic action, the stress orientations in the two zones show certain level of variability; (2) the stress patterns in both Zone A and Zone B of the project exhibit SH>Sh>Sv, with mainly the horizontal tectonic stress; (3) the orientation of the stress field is similar to that of the surrounding zones, and the stress concentration in Zone B has a stronger relationship with the topography, the stress difference between Zone B and Zone A gradually decreases as the test depth, and the indoor test results of rocks in the engineering zone further verify the distribution pattern of the stress field. 2021 Vol. 58 (4): 163-169 [Abstract] ( 480 ) [HTML 1KB] [ PDF 3464KB] ( 961 ) 170 Centrifugal Model Test on Construction Process of a Super Large Diameter Shield Tunnel Passing under Existing Railway YANG Linsong1 LIU Jiguo1 SHU Heng1 WU Shidong2 SONG Ming1 LI Jin1 WANG Xuetao2,3 The adjacent construction of a shield tunnel passing under operating high-speed railways will cause sub? grade settlement, uneven settlement of the track and other problems, which will affect the normal operation of the railway line and, in serious cases, also cause damage to the railway. In order to study the influence on settlement and settlement pattern of the intercity railways caused by the dynamic construction process of shield tunnels with super large diameters, based on the Wuhan Lianghu shield-driven highway tunnel with super large diameter and obliquely passing under the intercity railway, it simulates the whole dynamic process of the shield machine approaching-passing under-leaving the railway through geotechnical centrifuge model test. The research results show that: (1) the impact of shield tunnelling on the railway subgrade is mainly concentrated in the range of 25 m before and after the under-crossing point, while such impact beyond 25 m from the under-crossing point is quite small; (2) during the shield tunnelling process, the settlement of the railway subgrade caused by the tunnelling before under-crossing accounts for about 36% of the total railway subgrade settlement induced by tunnelling, while the settlement after under-crossing accounts for about 64%, and the settlement rate of the railway subgrade after the under-crossing increases rapidly and is greater than that before under-crossing; (3) taking 15 m where the shield has been passing under the railway as the dividing point, the settlement of the subgrade on the left side in the shield tunnelling direction is greater than that on the right side before the dividing point, and the opposite after, eventually the settlement of the railway subgrade on the right side in the shield tunnelling direction is greater than that on the left side. 2021 Vol. 58 (4): 170-177 [Abstract] ( 670 ) [HTML 1KB] [ PDF 3769KB] ( 1408 ) 178 Study on Liquefaction Characteristics of Medium-fine Sands in Shield Tunnelling with Small-size Shaking Table Test NING Maoquan1,2 XIAO Mingqing1 JIN Xuehui1,2 ZHAO Liya1,2 GUAN Zhenchang3 As for the <2-5> medium-fine sand stratum, in which the shield tunnel section of Fuzhou Metro Line 5 along Minjiang River locates, the small shaking table tests are performed under 9 orthogonal design conditions to explore the liquefaction characteristics of Minjiang sands. The results show that the excess pore water pressures and excess pore water pressure ratios at different depths quickly accumulate to the peak values in the initial excitation stage, then drop slightly and finally remain stable until the end of the excitation; the influence degrees of various factors on liquefaction of sands are ranked as follows: input wave amplitude>input frequency>soil saturation; for the sand stratum at shallow depth, it has higher liquefaction possibility, and slight, medium and complete liquefaction events might occur under action of designed earthquake, rare earthquake and huge earthquake, respectively. The test results can provide a basis for the parameter calibration in subsequent numerical simulations and a reference for engineering construction along the Minjiang River. 2021 Vol. 58 (4): 178-184 [Abstract] ( 537 ) [HTML 1KB] [ PDF 2522KB] ( 912 ) 185 Study on the Pattern of Temperature Propagation of Reinforced Concrete Structure under High-Temperature Environment ZHANG Qiushi1 ZHOU Chuansheng1 SUN Chunping2 LI Huayun1 GUO Zonglin1 The mechanical properties of reinforced concrete structures under high-temperature environment will be reduced to different degrees, seriously affecting the service life of the structures, however the temperature distribution pattern within the reinforced concrete structures is the basis for the analysis of the fire resistance of the components as well as for repair and reinforcement. In view of this, this paper carries out the indoor fire test to study the temperature propagation pattern within reinforced concrete structures under high-temperature environment based on the actual condition of the reinforced concrete lining of a prefabricated tunnel project in Chengdu. According to the indoor test results, this paper uses the numerical simulation method to optimize the concrete-related thermal parameters and obtains numerical simulation parameters more suitable for actual project condition, and also conducts a thermal coupling analysis on the prefabricated tunnel. The study results show that: (1) under single-sided fire con? dition, the closer a reinforced concrete beam is to the fire surface, the faster the heating rate and the higher the temperature will be; (2) the calculation formula of thermal conductivity is modified based on the finite element method,providing a certain level of reference for the selection of parameters for simulation calculation; (3) at the corners between the roof and the middle wall, sidewall it is prone to thermal stress concentration, which will cause greater damage to the structure and should be considered for strengthening in the tunnel fire protection design. 2021 Vol. 58 (4): 185-193 [Abstract] ( 608 ) [HTML 1KB] [ PDF 5315KB] ( 1128 ) 194 Analysis of Settlement Deformation and Construction Node Control of a Double-Line Shield Tunnelling Passing under Existing Tunnel in Close Distance GAO Lihong The deformation pattern of existing tunnels caused by the crossing construction of new urban rail proj? ects is a popular research topic in the engineering field. Based on a new shield tunnel passing under an existing one in close distance, this paper collates the actual measured data during the whole construction process. And in combination with the calculation results of the numerical model, it mainly analyzes the settlement deformation pattern of the existing double-line tunnel during the crossing construction process of the new left and right line tunnel tubes in turn, and further analyzes the stability of the disturbed soils in each construction stage. The results show that: (1)from the time dimension, there is a one-to-one correspondence between the vertical deformation trend of the existing structure and the construction stage during the crossing process; (2) from the distance dimension, the deformation of the tunnel structure increases as the distance from the crossing center decreases, and the pattern is consistent with the simulation results; (3) based on the amount and rate of deformations in the existing tunnel, the start stage of the crossing construction can be taken as a key node for controlling the settlement; (4) the settlement of the center area crossing the existing tunnel is much smaller than the simulated value, with achieving the actual redistribution of the settlement deformation, which verifies the effectiveness of construction key node control and the accuracy of the conclusions. 2021 Vol. 58 (4): 194-202 [Abstract] ( 563 ) [HTML 1KB] [ PDF 5105KB] ( 1322 ) 203 Study and Analysis of the Mechanism of Gas Emission (Outburst) in Miyaluo No.3 Tunnel on Wenchuan-Maerkang Highway DU Yi CHENG Qiang The gas emission from non-coal measure strata such as metamorphic sand slate and phyllite has the characteristics of random and uneven distribution. Taking Miyaluo No.3 tunnel on Wenchuan-Maerkang highway as the engineering background, this paper analyzes the geological background, gas geological characteristics and measured gas data regarding the tunnel, studies the mechanism and prevention measures of gas outburst in this kind of stratum. The study shows that the carbonaceous component in the sand slate has a certain capacity of hydrocarbon generation; via long and through fissures and fault fracture zones the gas is led from deeper stratum to shallow stratum; the gas is stored in densely developed joint zones, secondary bend fold zones and secondary fault fracture zones, where it is distributed in lenticular and bead-like pockets. If construction uncovers the closed cover around the lenticular gas and water storage structure, the broken rock, water and gas within the structure would suddenly gush out under the effect of water pressure and gas pressure, forming an outburst disaster. This type of gas has complex causal mechanisms and is difficult to predict, so comprehensive measures such as advance discharge, dilution and monitoring should be taken. 2021 Vol. 58 (4): 203-209 [Abstract] ( 516 ) [HTML 1KB] [ PDF 3524KB] ( 755 ) 210 Analysis of and Countermeasures against the Assembly Deviations of Prefabricated and Assembled Lane Structure in Double-deck Shield-driven Tunnels LIU Nian A shield-driven tunnel is a longitudinal flexible structure prone to such issues as dislocation and axis deviation, which are contrary to the requirements for high precision in prefabricated construction. In view of this, the common practice is to correct and eliminate shield tunnel deformation-induced deviations by means of cast-inplace strips and leveling layers in conjunction with the synchronous construction process in shield tunnelling. In other words, it is to form a monolithic prefabricated and assembled structure of "prefabricated main body + small amount of cast-in-place component". However, the space inside the shield-driven tunnel is so limited that excessive cast-in-place strips and over-thick leveling layers are not economical or time-efficient, and would also take up valuable internal space. Therefore, the cast-in-place strips and leveling layers should be set up in a reasonable manner so that they meet the need to eliminate longitudinal uneven deformations in shield-driven tunnels without taking up too much space. In light of this, this paper analyzes the characteristics of longitudinal uneven deformations in shield-driven tunnels based on the measured axis deviations in Shanghai Zhuguang Road tunnel and extant relevant literatures, and combined with the construction process it proposes a reasonable solution to eliminate longitudinal uneven deformations in shield tunnels with prefabricated and assembled lane structures, as well as a reasonable value for the thickness of the leveling layer. The results show that as for the upper prefabricated lane structure, the cast-in-place concrete base with bonded rebars could eliminate most of longitudinal uneven deformations in shielddriven tunnels, while leveling layers could eliminate a small amount of longitudinal uneven deformations and assembly deviations. For the lower prefabricated lane structure, longitudinal uneven deformations and assembly deviations in the shield-driven tunnel could be eliminated with leveling layers. The reasonable thickness of leveling layer for the upper and lower prefabricated lane structures is 100 mm and 130 mm respectively. 2021 Vol. 58 (4): 210-217 [Abstract] ( 527 ) [HTML 1KB] [ PDF 4454KB] ( 737 ) 218 Analysis of Construction Control Parameters in Rock Shield-driven Tunnelling YIN Sujiang1 YAN Shishun1 PEI Baizheng1 HUANG Dawei2,3 There are many factors influencing the construction parameters in shield tunnelling, and regarding the re? search on correlation among the construction parameters in shield tunnelling it is mainly based on theoretical analysis. It is difficult to clarify the influencing factors and mechanism of the construction parameters in shield tunnelling. This paper collects and analyzes the construction control parameters during EPB shield tunnelling in rock strata in Dalian, and the results show that: the correlation between the total thrust and advancing speed, the cutterhead rotation speed and torque, and the screw conveyor rotation speed and torque are all not significant; due to the significant soil arch effect in rock strata and thus the low frictional resistance between the shield shell and the surrounding rock, the total thrust is mainly used to provide the horizontal interaction between the cutterhead and the excavation face; the correlation between the rotation speed of the screw conveyor and the advancing speed of the shield machine is significant; the screw conveyor controls the fullness of the soil chamber through the rotation speed, influencing the excavated soils entering the chamber, so the muck discharge efficiency of the screw conveyor has a significant effect on the advancing speed and cutterhead torque. 2021 Vol. 58 (4): 218-223 [Abstract] ( 496 ) [HTML 1KB] [ PDF 2286KB] ( 1064 ) 224 Research on the Analysis Method for Segment Layout in Shield Tunnelling RUAN Chengzhi The layout of segments in curved shield tunnel sections is directly related to the construction quality of shield tunnels, while a reasonable segment layout option is beneficial to the posture control of shield machines and can reduce the gap deviation between a shield tunnel and shield tail brushes. This paper puts forward a new analysis and calculation method as well as related calculation formulas for the layout of segments in horizontal curved shield tunnel sections, and summarizes the principles of segment layout in horizontal curved sections. In circular curved sections, the segment layout follows the principle that the average deflection angle of the combined segment ring groups should be close to the arc length deflection angle of corresponding length of the segment span. In transition curved sections, a deviation correction dedicated segment ring group should be inserted when the cumulative deflection angle in a transition curved section reaches the deflection angle of a deviation correction dedicated segment ring group 2021 Vol. 58 (4): 224-228 [Abstract] ( 528 ) [HTML 1KB] [ PDF 829KB] ( 981 ) 229 Analysis on Reinforcement Effect of Surface Grouting in Shallow-Buried Tunnels with Asymmetrical Loading and Abundant Underground Water YE Xinxin1 MIAO Miao2 ZHONG Yujian2 XU Shuoshuo2 DU Ke2 In order to study the reinforcement effect of surface pre-grouting in fractured soft rock tunnels with shal? low depth and asymmetrical loading, this paper establishes a 3D finite element model based on the Hongshihe tunnel project which adopts sleeve valve pipe grouting for reinforcement, and conducts a comparative analysis on the grouting reinforcement effect through field tests, monitoring and measurement. Comprehensive analysis shows that after the surface grouting, the strength and integrity of the surrounding rocks are significantly improved, the water permeability of the rock mass is reduced, the arching capacity of the ground is enhanced, and the overall stress characteristics of the tunnel support structure are greatly improved. The maximum axial compressive force of the initial support is reduced by nearly 20%, while the maximum axial tensile force is 43% of the original value; the maximum positive bending moment of the initial support is reduced by 58% while the maximum negative bending moment is reduced by 29%; the changing trends of tunnel vault settlement and surrounding rock convergence are basically the same, with about 70% of the total deformation completed in the first 10-15 days, and the whole deformation basically completed in 20-25 days. And the numerical calculation is consistent with the field measurement results, with a very significant grouting effect. 2021 Vol. 58 (4): 229-236 [Abstract] ( 831 ) [HTML 1KB] [ PDF 5090KB] ( 857 ) 237 Research on the Detection and Treatment Technology for Highway Tunnel Defects YANG Chunping HU Qiang The problem of highway tunnel defects has become an unavoidable factor that affects traffic safety. Based on the context of Jizhao tunnel on Xiamen-Chengdu expressway, this paper conducts tests on the lining concrete strength, tunnel inner contour condition in terms of various tunnel defects, such as lining cracking, cable groove sinking and sidewall seepage, analyzes the causes of tunnel defects based on the testing results, and proposes reasonable treatment options: (1) using the foot-locking and grouting perforated steel pipes, and installing additional plain concrete inverted arch or reinforced concrete invert arch to effectively improve the stability of the tunnel structure; (2) setting up transverse drainage pipes in the additional inverted arch section in combination with longitudinal drainage pipes to ensure smooth drainage; (3) re-pouring the secondary lining sidewalls with severe deformation,cracking and spalling, in combination with installation of low pre-stressed anchor bolts and steel strips to anchor the secondary lining and the surrounding rock as a whole. These methods can provide certain references for treating the defects of existing tunnels. 2021 Vol. 58 (4): 237-245 [Abstract] ( 594 ) [HTML 1KB] [ PDF 6449KB] ( 1302 )

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