Due to space constraints in urban areas,metro tunnels are typically constructed in pairs,with a small clearance.The interaction between twin tunnels leads to a significantly more complex ground deformation and stress ...Due to space constraints in urban areas,metro tunnels are typically constructed in pairs,with a small clearance.The interaction between twin tunnels leads to a significantly more complex ground deformation and stress distribution than that observed in a single tunnel scenario,particularly if the tunnels are excavated in sequence.A series of physical model tests were conducted to investigate soil deformation and stress disturbances caused by the excavation of twin tunnels.The test results indicate that the interaction between the twin tunnels was observed.Due to the soil arching effect,the excavation of Tunnel 2 increases the soil stress acting on Tunnel 1.An analytical method was proposed to determine soil stress considering the soil arching effect and the interaction between twin tunnels.The method categorized the relative locations between twin tunnels into non-influenced,partially influenced,and fully influenced scenarios.For non-influenced and fully influenced scenarios,the soil stresses above twin tunnels were calculated based on a symmetric major principal stress trace.For the partially influenced scenario,however,the soil arch above Tunnel 2 was asymmetric due to the interaction,and the stress distribution was obtained based on a new asymmetric major principal stress trace.The soil stress on Tunnel 1 was influenced by the load transferred from Tunnel 2 and calculated based on the force equilibrium.A comparison of the analytical and test results indicates that the proposed method effectively predicts the soil stress in the cover layer above twin tunnels excavated sequentially,considering the interaction and soil arching effects.展开更多
To discuss the soil arching effect on the load transferring model and sharing ratios by the piles and inter-pile subsoil in the bidirectionally reinforced composite ground, the forming mechanism, mechanical behavior a...To discuss the soil arching effect on the load transferring model and sharing ratios by the piles and inter-pile subsoil in the bidirectionally reinforced composite ground, the forming mechanism, mechanical behavior and its effect factors were discussed in detail. Then, the unified strength theory was introduced to set up the elastoplastic equilibrium differential equation of the subsoil under the limit equilibrium state. And from the equation, the solutions were derived with the corresponding formulas presented to calculate the earth pressure over and beneath the horizontal reinforced cushion or pillow, the stress of inter-pile subsoil and the pile-soil stress ratio. Based on the obtained solutions and measured data from an engineering project, the influence rules by the soil property parameters (i.e., the cohesion c and internal friction angle φ) and pile spacing on the pile-soil stress ratio n were discussed respectively. The results show that to improve the load sharing ratio by the piles, the more effective means for filling materials with a larger value of φ is to increase the ratio of pile cap size to spacing, while to reduce the pile spacing properly and increase the value of cohesion c is advisable for those filling materials with a smaller value of φ.展开更多
Combined with practical engineering, based on the introduction of soil arching theory, we explore the impact of barrier piles in blind sheet-pile bank connecting structure. Besides, we build a plane strain model by AB...Combined with practical engineering, based on the introduction of soil arching theory, we explore the impact of barrier piles in blind sheet-pile bank connecting structure. Besides, we build a plane strain model by ABAQUS sot＇cware to study the impact of cross section type, the pile spacing and soil properties on soil arching effect. We find that cross section type of the pile has a certain influence on soil stress distribution in front of the barrier piles by comparing circular cross section and rectangular cross section. We also find that clear distance between the barrier piles and cohesive force of the soil have a great influence on that impact. We can increase clear distance between the barrier piles appropriately to improve the efficiency of construction and reduce the proiect cost.展开更多
To determine the distribution of active earth pressure on retaining walls, a series of model tests with the horizontally translating rigid walls are designed. Particle image velocimetry is used to study the movement a...To determine the distribution of active earth pressure on retaining walls, a series of model tests with the horizontally translating rigid walls are designed. Particle image velocimetry is used to study the movement and shear strain during the active failure of soil with height H and friction angle φ. The test results show that there are 3 stages of soil deformation under retaining wall translation: the initial stage, the expansion stage and the stability stage. The stable sliding surface in the model tests can be considered to be composed of two parts. Within the height range of 0.82 H-1.0 H, it is a plane at an angle of π/4+φ/2 to the horizontal plane. In the height range of 0-0.82 H, it is a curve between a logarithmic spiral and a plane at an angle of π/4+φ/2 to the horizontal. A new method applicable to any sliding surface is proposed for active earth pressure with the consideration of arching effect. The active earth pressure is computed with the actual shape of the slip surface and compared with model test data and with predictions obtained by existing methods. The comparison shows that predictions from the newly proposed method are more consistent with the measured data than the predictions from the other methods.展开更多
The soil arching effect induced by deep-buried shield tunneling strongly influenced the ground stress and displacement.Therefore,revealing the evolution mechanism of the soil arching effect is a prerequisite for accur...The soil arching effect induced by deep-buried shield tunneling strongly influenced the ground stress and displacement.Therefore,revealing the evolution mechanism of the soil arching effect is a prerequisite for accurately predicting the tunnel load,which has not been understood in deep-buried conditions.Three model tests and eight numerical simulations were carried out to enhance the understanding of the soil arching evolution,in which the stress field,displacement field,and strain field were analysed.The experimental and numerical results indicated that the ground reaction curve presented a two-stage development process of an initially linear decrease followed by a gradual decrease.Compared with the theoretical tunnel loads,the measured and numerical values are relatively larger due to the loosening earth pressure theory ignoring the evolution process of the soil arching effect.The soil arching height decreases with the increase in stress level,measuring 1.75D(the initial diameter of the model tunnel),1.65D,and 1.61D,respectively,which results from the lagging evolution of the soil arching effect under high-stress conditions.The formation of the shear band was affected by the stress-dependent dilatancy of the soil.At low stress levels,the shear band develops vertically upward.In contrast,at higher stress levels,the shear bands tilt towards the lateral side.展开更多
The computation of the design load on culverts in the current Chinese General Code for Design of Highway Bridges and Culverts （CGCDHBC）is primarily based on the linear earth pressure theory, which cannot accurately ...The computation of the design load on culverts in the current Chinese General Code for Design of Highway Bridges and Culverts （CGCDHBC）is primarily based on the linear earth pressure theory, which cannot accurately reflect the changes in vertical loads on trench installation culverts. So the changes in vertical earth pressure and soil arching effect in the backfill for an unsymmetrical trench installation culvert are studied based on a full scale experiment and finite element （FE） simulation. The variation laws of foundation pressure and settlement are also analyzed. Meanwhile, the influence of eccentric load induced by an unsymmetrical trench installation on the interaction of a soil- structure system is discussed. Results show that soil arch is formed when the backfill on the culvert reaches a certain height. It can relieve the earth pressure concentration on the crest of the culvert, but it is instable. The earth pressures obtained by full scale experiment and numerical simulation are greater than those calculated by the current CGCDHBC method. The eccentric load effect on the culvert has a significant influence on the stress states and deformation of the soil-structure system.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.52308463)the Shanghai Rising-Star Program(Grant No.23YF1449100)the Fundamental Research Funds for the Central Universities(Grant No.2023-2-ZD08).
文摘Due to space constraints in urban areas,metro tunnels are typically constructed in pairs,with a small clearance.The interaction between twin tunnels leads to a significantly more complex ground deformation and stress distribution than that observed in a single tunnel scenario,particularly if the tunnels are excavated in sequence.A series of physical model tests were conducted to investigate soil deformation and stress disturbances caused by the excavation of twin tunnels.The test results indicate that the interaction between the twin tunnels was observed.Due to the soil arching effect,the excavation of Tunnel 2 increases the soil stress acting on Tunnel 1.An analytical method was proposed to determine soil stress considering the soil arching effect and the interaction between twin tunnels.The method categorized the relative locations between twin tunnels into non-influenced,partially influenced,and fully influenced scenarios.For non-influenced and fully influenced scenarios,the soil stresses above twin tunnels were calculated based on a symmetric major principal stress trace.For the partially influenced scenario,however,the soil arch above Tunnel 2 was asymmetric due to the interaction,and the stress distribution was obtained based on a new asymmetric major principal stress trace.The soil stress on Tunnel 1 was influenced by the load transferred from Tunnel 2 and calculated based on the force equilibrium.A comparison of the analytical and test results indicates that the proposed method effectively predicts the soil stress in the cover layer above twin tunnels excavated sequentially,considering the interaction and soil arching effects.
基金Project (07JJ4015) supported by the Natural Science Foundation of Hunan Province, China
文摘To discuss the soil arching effect on the load transferring model and sharing ratios by the piles and inter-pile subsoil in the bidirectionally reinforced composite ground, the forming mechanism, mechanical behavior and its effect factors were discussed in detail. Then, the unified strength theory was introduced to set up the elastoplastic equilibrium differential equation of the subsoil under the limit equilibrium state. And from the equation, the solutions were derived with the corresponding formulas presented to calculate the earth pressure over and beneath the horizontal reinforced cushion or pillow, the stress of inter-pile subsoil and the pile-soil stress ratio. Based on the obtained solutions and measured data from an engineering project, the influence rules by the soil property parameters (i.e., the cohesion c and internal friction angle φ) and pile spacing on the pile-soil stress ratio n were discussed respectively. The results show that to improve the load sharing ratio by the piles, the more effective means for filling materials with a larger value of φ is to increase the ratio of pile cap size to spacing, while to reduce the pile spacing properly and increase the value of cohesion c is advisable for those filling materials with a smaller value of φ.
文摘Combined with practical engineering, based on the introduction of soil arching theory, we explore the impact of barrier piles in blind sheet-pile bank connecting structure. Besides, we build a plane strain model by ABAQUS sot＇cware to study the impact of cross section type, the pile spacing and soil properties on soil arching effect. We find that cross section type of the pile has a certain influence on soil stress distribution in front of the barrier piles by comparing circular cross section and rectangular cross section. We also find that clear distance between the barrier piles and cohesive force of the soil have a great influence on that impact. We can increase clear distance between the barrier piles appropriately to improve the efficiency of construction and reduce the proiect cost.
基金Projects(51978084, 51678073) supported by the National Natural Science Foundation of ChinaProject(2020JJ4605) supported by the Natural Science Foundation of Hunan Province, ChinaProject(2019IC13) supported by the International Cooperation and Development Project of Double First-Class Scientific Research in Changsha University of Science & Technology, China。
文摘To determine the distribution of active earth pressure on retaining walls, a series of model tests with the horizontally translating rigid walls are designed. Particle image velocimetry is used to study the movement and shear strain during the active failure of soil with height H and friction angle φ. The test results show that there are 3 stages of soil deformation under retaining wall translation: the initial stage, the expansion stage and the stability stage. The stable sliding surface in the model tests can be considered to be composed of two parts. Within the height range of 0.82 H-1.0 H, it is a plane at an angle of π/4+φ/2 to the horizontal plane. In the height range of 0-0.82 H, it is a curve between a logarithmic spiral and a plane at an angle of π/4+φ/2 to the horizontal. A new method applicable to any sliding surface is proposed for active earth pressure with the consideration of arching effect. The active earth pressure is computed with the actual shape of the slip surface and compared with model test data and with predictions obtained by existing methods. The comparison shows that predictions from the newly proposed method are more consistent with the measured data than the predictions from the other methods.
基金supported by the National Natural Science Foundation of China(Grant Nos.52090082 and 51938005).
文摘The soil arching effect induced by deep-buried shield tunneling strongly influenced the ground stress and displacement.Therefore,revealing the evolution mechanism of the soil arching effect is a prerequisite for accurately predicting the tunnel load,which has not been understood in deep-buried conditions.Three model tests and eight numerical simulations were carried out to enhance the understanding of the soil arching evolution,in which the stress field,displacement field,and strain field were analysed.The experimental and numerical results indicated that the ground reaction curve presented a two-stage development process of an initially linear decrease followed by a gradual decrease.Compared with the theoretical tunnel loads,the measured and numerical values are relatively larger due to the loosening earth pressure theory ignoring the evolution process of the soil arching effect.The soil arching height decreases with the increase in stress level,measuring 1.75D(the initial diameter of the model tunnel),1.65D,and 1.61D,respectively,which results from the lagging evolution of the soil arching effect under high-stress conditions.The formation of the shear band was affected by the stress-dependent dilatancy of the soil.At low stress levels,the shear band develops vertically upward.In contrast,at higher stress levels,the shear bands tilt towards the lateral side.
基金Key Plan of Science and Technology of Hubei Provincial Communication Department(No.2005-361)
文摘The computation of the design load on culverts in the current Chinese General Code for Design of Highway Bridges and Culverts （CGCDHBC）is primarily based on the linear earth pressure theory, which cannot accurately reflect the changes in vertical loads on trench installation culverts. So the changes in vertical earth pressure and soil arching effect in the backfill for an unsymmetrical trench installation culvert are studied based on a full scale experiment and finite element （FE） simulation. The variation laws of foundation pressure and settlement are also analyzed. Meanwhile, the influence of eccentric load induced by an unsymmetrical trench installation on the interaction of a soil- structure system is discussed. Results show that soil arch is formed when the backfill on the culvert reaches a certain height. It can relieve the earth pressure concentration on the crest of the culvert, but it is instable. The earth pressures obtained by full scale experiment and numerical simulation are greater than those calculated by the current CGCDHBC method. The eccentric load effect on the culvert has a significant influence on the stress states and deformation of the soil-structure system.
