According to the interaction of three shallow tunnels with large section, the analytical solution to rock pressure has been derived and discussed. The load model is given when the bilateral tunnels are excavated. Acco...According to the interaction of three shallow tunnels with large section, the analytical solution to rock pressure has been derived and discussed. The load model is given when the bilateral tunnels are excavated. According to the model, the stresses of three tunnels and single tunnel are calculated and compared to analyze the distribution characteristics, where the stresses are influenced by controlling factors of clear distance, covering depth and inclination angle of ground surface. The results show that, in general, the bias distribution is more serious. Therefore, it is significant to settle down the load model of three shallow tunnels so as to determine the measure of reinforcement and design the structure of support. The model and results can be used as a theoretical basis in designation and further research of the three shallow tunnels.展开更多
Using an MTS816.03 test system and self-designed seepage apparatus, seepage tests of saturated broken rocks were conducted, and the influence of lithology, axial stress, grain size distribution and loading rate on see...Using an MTS816.03 test system and self-designed seepage apparatus, seepage tests of saturated broken rocks were conducted, and the influence of lithology, axial stress, grain size distribution and loading rate on seepage characteristics was analyzed. The results show that： （1） Under the same axial stress （12 MPa）, the permeability of different lithologic samples increases in the order： gangue 〈 mudstone 〈 sandstone 〈 limestone. The permeability of gangue is 3 magnitudes lower than that of limestone. The absolute value of the non-Darcy coefficient β increases in the order： limestone 〈 sandstone 〈 mudstone 〈 gangue. The non-Darcy coefficient β of limestone, which is positive, is 5 magnitudes lower than that of gangue. （2） With increasing axial stress, the permeability of saturated broken sandstone decreases, and the absolute value of the non-Darcy coefficient β increases. After the axial stress exceeds 12 MPa, the curves of permeability and non-Darcy coefficient β all tend to be stable. （3） With increasing Talbol power exponent, the permeability increases, and the absolute value of the non-Darcy coefficient β decreases. （4） With increasing loading, the permeability increases, and the absolute value of the non-Darcy coefficient β decreases. When the loading rate is 0.5 kN/s, the non-Darcy coefficient β is positive.展开更多
Three Dimensional Finite Element Method(3D-FEM)has been used to model the deviatoric stress field in a forsterite aggregate with a sandwich geometry:two forsterite cubes aligned in the same crystallographic orientatio...Three Dimensional Finite Element Method(3D-FEM)has been used to model the deviatoric stress field in a forsterite aggregate with a sandwich geometry:two forsterite cubes aligned in the same crystallographic orientation(the"breads")sandwich a third forsterite cube(the"filling"),which might have an identical or different crystallographic orientation.The results show that there is no von Mises stress in the forsterite sandwich if the sandwiching and sandwiched forsterite cubes are aligned in the same crystallographic orientation.If the crystallographic orientations are different,however,von Mises stress and heterogeneous stress distribution occur both along the boundary and in the forsterite cubes.For the investigated P-T conditions(up to 6.4GPa and 500°C),the resulted deviatoric stress is much lower than the yield strength of forsterite,so that higher P,higher T,or other means to create higher deviatoric stress is necessary,in order to constrain the yielding behavior of forsterite.展开更多
基金Projects(2013CB036004, 2011CB013800) supported by the National Basic Research Program of ChinaProject(51178468, 50908234) supported by the National Natural Science Foundation of ChinaProject(2011G103-B) supported by the Science and Technology Development of Railway in China
文摘According to the interaction of three shallow tunnels with large section, the analytical solution to rock pressure has been derived and discussed. The load model is given when the bilateral tunnels are excavated. According to the model, the stresses of three tunnels and single tunnel are calculated and compared to analyze the distribution characteristics, where the stresses are influenced by controlling factors of clear distance, covering depth and inclination angle of ground surface. The results show that, in general, the bias distribution is more serious. Therefore, it is significant to settle down the load model of three shallow tunnels so as to determine the measure of reinforcement and design the structure of support. The model and results can be used as a theoretical basis in designation and further research of the three shallow tunnels.
基金provided by the National Basic Research Program of China (No.2013CB227900)the Ordinary University Graduate Student Research Innovation Project in Jiangsu Province for 2014 (No.KYLX_1370)the National Natural Science Foundation of China (Nos.11502229 and 51404266)
文摘Using an MTS816.03 test system and self-designed seepage apparatus, seepage tests of saturated broken rocks were conducted, and the influence of lithology, axial stress, grain size distribution and loading rate on seepage characteristics was analyzed. The results show that： （1） Under the same axial stress （12 MPa）, the permeability of different lithologic samples increases in the order： gangue 〈 mudstone 〈 sandstone 〈 limestone. The permeability of gangue is 3 magnitudes lower than that of limestone. The absolute value of the non-Darcy coefficient β increases in the order： limestone 〈 sandstone 〈 mudstone 〈 gangue. The non-Darcy coefficient β of limestone, which is positive, is 5 magnitudes lower than that of gangue. （2） With increasing axial stress, the permeability of saturated broken sandstone decreases, and the absolute value of the non-Darcy coefficient β increases. After the axial stress exceeds 12 MPa, the curves of permeability and non-Darcy coefficient β all tend to be stable. （3） With increasing Talbol power exponent, the permeability increases, and the absolute value of the non-Darcy coefficient β decreases. （4） With increasing loading, the permeability increases, and the absolute value of the non-Darcy coefficient β decreases. When the loading rate is 0.5 kN/s, the non-Darcy coefficient β is positive.
基金supported by National Natural Science Foundation of China(Grant No.41090371)
文摘Three Dimensional Finite Element Method(3D-FEM)has been used to model the deviatoric stress field in a forsterite aggregate with a sandwich geometry:two forsterite cubes aligned in the same crystallographic orientation(the"breads")sandwich a third forsterite cube(the"filling"),which might have an identical or different crystallographic orientation.The results show that there is no von Mises stress in the forsterite sandwich if the sandwiching and sandwiched forsterite cubes are aligned in the same crystallographic orientation.If the crystallographic orientations are different,however,von Mises stress and heterogeneous stress distribution occur both along the boundary and in the forsterite cubes.For the investigated P-T conditions(up to 6.4GPa and 500°C),the resulted deviatoric stress is much lower than the yield strength of forsterite,so that higher P,higher T,or other means to create higher deviatoric stress is necessary,in order to constrain the yielding behavior of forsterite.
