Mixed-face ground encountered in Tunnel Boring Machine(TBM) tunneling presents great challenges and may trigger potential hazards without warning. A detailed understanding of such unfavorable conditions is therefore c...Mixed-face ground encountered in Tunnel Boring Machine(TBM) tunneling presents great challenges and may trigger potential hazards without warning. A detailed understanding of such unfavorable conditions is therefore critical to a successful bored tunnel. In this paper, we firstly present a brief review of the definition, classification and the factors related to mixed-face conditions. Secondly, for a better understanding of this topic, we investigate the main difficulties and problems involved in TBM tunnelling under mixed-face ground with detailed cases. Thirdly, from the viewpoint of rock-machine interaction, we give some suggestions on the corresponding mitigation measurements from three categories:(i) selection of TBM type and modification of TBM,(ii) condition of ground and(iii) optimization of TBM operation.展开更多
Using a finite element method （FEM） program, a Portland cement concrete slab trackbed （So）, and a sub- track asphalt roadbed （RAC-S） were modeled under high- speed train loads to analyze their responses to groun...Using a finite element method （FEM） program, a Portland cement concrete slab trackbed （So）, and a sub- track asphalt roadbed （RAC-S） were modeled under high- speed train loads to analyze their responses to ground vibration attenuation, by considering 10, 15, 20, 25, and 30 thick sub-track asphalt layer replaced on the top of the upper subgrade. FEM results show that the vibration amplitude of RAC-S is at least three times lower than the vibration for So. The maximum vibration amplitude of RAC-S is linearly increased with train speed. The vertical acceleration is found to be reduced by more than 10 % when the asphalt layer thickness is increased from 10 to 20 cm. However, the reduction in vertical acceleration is only about 1% when the thickness of the asphalt layer changes from 20 to 30 cm. The vibration level is slightly lower if the asphalt layer has higher resilient modulus in the seasons of autumn or winter. This theoretical analysis indicates that a railway substructure that consists of a 10-20 cm thick high modulus asphalt layer located at the top of trackbed shows a good performance in ground vibration control for high-speed rails.展开更多
A considerable amount of tunnelling has been going on in India for various projects such as hydroelectric power, irrigation, roads and railways. Most of these projects are located in Himalayas, far away from the urban...A considerable amount of tunnelling has been going on in India for various projects such as hydroelectric power, irrigation, roads and railways. Most of these projects are located in Himalayas, far away from the urban areas. Tunnelling through weak and jointed rock masses such as the one in the Himalayas is a challenging task for the planners, designers, engineers and geologists because of high overburden, thickly vegetated surface, weak, poor and fragile rocks and highly varying geology with the presence of numerous small and big shear zones, faults, etc. Due to these reasons, various tunnelling problems have been faced in the past and are still being encountered. Failures and the problems may be regarded as challenges and opportunities for generating new knowledge base and thereby increasing self-reliance in tunnelling. The experiences of Himalayan tunnelling through weak and fragile rocks covering varying and mixed geology, understanding on tunnelling in squeezing ground conditions and applicability of TBM in Himalayas are presented. It has also been highlighted that the probe holes planning, drilling and monitoring shall be followed seriously to reduce the geological surprises.展开更多
Rock-soil interface mixed ground(RSI)is often encountered in tunnel construction.The excavation loads of tunnel boring machines(TBMs)are controlled by the interaction characteristics between TBM and rock/soil layers.T...Rock-soil interface mixed ground(RSI)is often encountered in tunnel construction.The excavation loads of tunnel boring machines(TBMs)are controlled by the interaction characteristics between TBM and rock/soil layers.The different properties of rock and soil cause the varying interaction range and stress distribution.Currently,there have been several studies available to estimate excavation loads under RSI,and the conclusion is that the total loads increase with increasing the rock layer proportion in the excavation face.However,the previous studies cannot take the difference of rock/soil properties into account,except for the calculation of cutters loads.Therefore,the interaction characteristics between RSI and TBM is unclear.This paper analyzes the interaction characteristics between TBM’s main components and complex geological conditions(e.g.,layered soil,layered rock,and RSI condition).A model is proposed to calculate the total thrust and total torque assuming quasi-static equilibrium of the tunneling equipment.The rationality and applicability of the model are discussed and verified by two typical projects.Furthermore,the geological adaptability is discussed in terms of the excavation difficulty and the matching relationship between total torque and total thrust.The results indicate that when the rock layer proportion in the excavation face increases,the reduction of overall extrusion and friction loads is 1.5 times higher than the increase of disc cutters breaking load.The total loads and the ratio of the total torque to total thrust decrease approximately linearly.There is a power function relationship between the excavation difficulty index and the penetration depth.The results of this study provide an important reference for the total loads design of equipment propulsion systems and the parameter adjustment during tunnel construction.展开更多
基金Financial supports from the National Natural Science Foundation of China(No.51308196)
文摘Mixed-face ground encountered in Tunnel Boring Machine(TBM) tunneling presents great challenges and may trigger potential hazards without warning. A detailed understanding of such unfavorable conditions is therefore critical to a successful bored tunnel. In this paper, we firstly present a brief review of the definition, classification and the factors related to mixed-face conditions. Secondly, for a better understanding of this topic, we investigate the main difficulties and problems involved in TBM tunnelling under mixed-face ground with detailed cases. Thirdly, from the viewpoint of rock-machine interaction, we give some suggestions on the corresponding mitigation measurements from three categories:(i) selection of TBM type and modification of TBM,(ii) condition of ground and(iii) optimization of TBM operation.
基金supported by National Natural Science Foundation of China(No.51308429)the Fundamental Research Funds for the Central University(WUT:2013-IV-067)Opening Funds for Highway Engineering Key Laboratory of Sichuan Province(No.LHTE004201304)
文摘Using a finite element method （FEM） program, a Portland cement concrete slab trackbed （So）, and a sub- track asphalt roadbed （RAC-S） were modeled under high- speed train loads to analyze their responses to ground vibration attenuation, by considering 10, 15, 20, 25, and 30 thick sub-track asphalt layer replaced on the top of the upper subgrade. FEM results show that the vibration amplitude of RAC-S is at least three times lower than the vibration for So. The maximum vibration amplitude of RAC-S is linearly increased with train speed. The vertical acceleration is found to be reduced by more than 10 % when the asphalt layer thickness is increased from 10 to 20 cm. However, the reduction in vertical acceleration is only about 1% when the thickness of the asphalt layer changes from 20 to 30 cm. The vibration level is slightly lower if the asphalt layer has higher resilient modulus in the seasons of autumn or winter. This theoretical analysis indicates that a railway substructure that consists of a 10-20 cm thick high modulus asphalt layer located at the top of trackbed shows a good performance in ground vibration control for high-speed rails.
文摘A considerable amount of tunnelling has been going on in India for various projects such as hydroelectric power, irrigation, roads and railways. Most of these projects are located in Himalayas, far away from the urban areas. Tunnelling through weak and jointed rock masses such as the one in the Himalayas is a challenging task for the planners, designers, engineers and geologists because of high overburden, thickly vegetated surface, weak, poor and fragile rocks and highly varying geology with the presence of numerous small and big shear zones, faults, etc. Due to these reasons, various tunnelling problems have been faced in the past and are still being encountered. Failures and the problems may be regarded as challenges and opportunities for generating new knowledge base and thereby increasing self-reliance in tunnelling. The experiences of Himalayan tunnelling through weak and fragile rocks covering varying and mixed geology, understanding on tunnelling in squeezing ground conditions and applicability of TBM in Himalayas are presented. It has also been highlighted that the probe holes planning, drilling and monitoring shall be followed seriously to reduce the geological surprises.
基金funded by National Key R&D Program of China[No.2018YFB1702505]National Natural Science Foundation of China[Grant Nos.12022205 and 11872269].
文摘Rock-soil interface mixed ground(RSI)is often encountered in tunnel construction.The excavation loads of tunnel boring machines(TBMs)are controlled by the interaction characteristics between TBM and rock/soil layers.The different properties of rock and soil cause the varying interaction range and stress distribution.Currently,there have been several studies available to estimate excavation loads under RSI,and the conclusion is that the total loads increase with increasing the rock layer proportion in the excavation face.However,the previous studies cannot take the difference of rock/soil properties into account,except for the calculation of cutters loads.Therefore,the interaction characteristics between RSI and TBM is unclear.This paper analyzes the interaction characteristics between TBM’s main components and complex geological conditions(e.g.,layered soil,layered rock,and RSI condition).A model is proposed to calculate the total thrust and total torque assuming quasi-static equilibrium of the tunneling equipment.The rationality and applicability of the model are discussed and verified by two typical projects.Furthermore,the geological adaptability is discussed in terms of the excavation difficulty and the matching relationship between total torque and total thrust.The results indicate that when the rock layer proportion in the excavation face increases,the reduction of overall extrusion and friction loads is 1.5 times higher than the increase of disc cutters breaking load.The total loads and the ratio of the total torque to total thrust decrease approximately linearly.There is a power function relationship between the excavation difficulty index and the penetration depth.The results of this study provide an important reference for the total loads design of equipment propulsion systems and the parameter adjustment during tunnel construction.
