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Ai H.-J.,Central South University | Peng L.-M.,Central South University | Peng L.-M.,National Engineering Laboratory of High Speed Railway Construction | Shi C.-H.,Central South University | Shi C.-H.,National Engineering Laboratory of High Speed Railway Construction
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2013

Based on the nonlinear contact theory and considering the discontinuity of shield tunnel structure, a three-dimensional discontinuous contact model for track bed-segment-surrounding rocks is established by simulating the segment joints and the interaction between the segment and the surrounding rocks as well as the track bed. The mechanical and deformation properties of the segment joints under the pressure of the surrounding rocks and the action of the subway train dynamic load are analyzed in depth based on this model. The results of numerical simulations show that under the pressure of the surrounding rocks, some longitudinal joints in arch crown area and arch bottom open inwards; some joints in haunch of shield tunnel open outwards; and the dislocations between the completed blocks and the adjacent blocks in arch crown area are comparatively large. The joints in haunch are compressed obviously and those in arch crown have the minimum pressure under the pressure of the surrounding rocks. The axial forces of joint bolts in vault area are relatively the greatest, those in arch bottom come second, and those in haunch are the smallest. The shearing forces of joint bolts in the top of arch foots are also the greatest when segment ring rotates to an angle so as to complete assembly. The opens and dislocations of the segment joints, concrete stress and internal forces of joint bolts all increase rapidly at the beginning of the dynamic load, then significantly decrease, and finally are fluctuant under the action of dynamic load of subway trains. The dynamic response of joints in arch crown is more obvious than that in arch bottom for shallow buried metro tunnels. The shearing forces of joint bolts increase more than the axial forces under the action of dynamic load of subway trains. Source


Lei M.,Central South University | Peng L.,Central South University | Peng L.,National Engineering Laboratory of High Speed Railway Construction | Shi C.,Central South University | And 3 more authors.
Zhongnan Daxue Xuebao (Ziran Kexue Ban)/Journal of Central South University (Science and Technology) | Year: 2014

Using the dynamic finite difference method, the dynamic response of double arch tunnel in Kast region of Baiyunshan tunnel on Yichang-Wanzhou railway was analyzed. The calculating method of the cumulative deformation of Kast foundation under long-term train loading was discussed further based on Dingqing Li plastic strain model. The results show that the vibration of typical positions of Baiyunshan double arch tunnel in Kast region is small, and both the tensile and compressive peak value and the displacement are less than the design values; Under the long-term train loading (i. e. 100 a), the cumulative plastic deformation of Kast foundation is less than 20 mm, which can satisfy the smooth requirement of line to high speed train. Source


Ding Z.-D.,Central South University | Peng L.-M.,Central South University | Peng L.-M.,National Engineering Laboratory of High Speed Railway Construction | Shi C.-H.,Central South University | And 3 more authors.
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2012

Through the dynamic triaxial tests on water-rich sandy mudstone, the dynamic strain analysis is made on the water-rich sandy mudstone under cyclic loading, and the influences of dynamic stress, static deviator stress and vibration frequency are analyzed emphatically. The results show that there are two types of cumulative irreversible deformation of water-rich sandy mudstone under cyclic loading, i.e. stable type and destructive type. The development of deformation can be divided into the initial and the stable stages for the stable development curve, and the cumulative deformation during initial stage is of the total deformation of 40% to 50%, but the proportion decreases with the increase of stress level. For the destructive development curve, there are three stages: the initial deformation stage, the constant deformation stage and the accelerative deformation stage. The cumulative plastic deformation of the sandy mudstone grows with the increase of the dynamic stress and static deviator stress and reduces with the increase of the vibration frequency, especially at a higher dynamic stress, higher static deviator stress or less frequency. There is a critical dynamic stress under cyclic loading, which depends on rock property, stress level and vibration frequency. Source


Shi C.-H.,Central South University | Shi C.-H.,National Engineering Laboratory of High Speed Railway Construction | Lei M.-F.,Central South University | Peng L.-M.,Central South University | And 3 more authors.
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2012

By means of the in-situ monitoring method, the deformation of bottom structure of tunnel and the stress of concrete and rebars in its inverted arch are tested and analyzed. Under the action of unloading of surrounding rock, the loads of tunnel linings, and the upper surrounding rock auxiliary facilities and train load, the bottom structure of the tunnel witnesses a repeated process of uplift-subsidence-uplift-subsidence during the whole course of tunnel construction, and the concrete and rebars in the inverted arch have a process of tension-compression-tension-compression as well. The better the condition of the surrounding rock, the smaller the values of the deformation and stress and their change ranges. During the whole course of tunnel construction, the maximum subsidence of the bottom structure of the tunnel is less than 5.0 mm, and the maximum tensile and compression stresses are both less than 2.0 MPa, thus high-speed trains can run safely. The inverted arch of the tunnel is in the worst conditions before the tunnel linings are constructed. So the tunnel linings must be constructed in time to make sure that the inverted arch is under better conditions. The redistribution time of the stress on the surrounding rock after tunnel excavation is generally more than two years. Source


Shi C.-H.,Central South University | Shi C.-H.,National Engineering Laboratory of High Speed Railway Construction | Ding Z.-D.,Central South University | Lei M.-F.,Central South University | And 2 more authors.
Rock Mechanics and Rock Engineering | Year: 2014

An experimental study on the dynamic deformation behaviors of water-rich mudstone under cyclic loading was conducted. The rock samples used in the experiment were collected from a tunnel located at 1030 m under the ground. The increase in the accumulation of irreversible plastic strain for water-rich mudstones under cyclic loadings leads to two different results, stabilization under low dynamic stress amplitude and failure under high dynamic stress amplitude. The results suggest that the critical stress limit for the tested water-rich mudstone is between 180 and 300 kPa. The vibration frequency affects the deformation characteristic and critical stress of water-rich mudstone. With other variables kept constant, lower frequencies result in higher deformation of the rock samples. Groundwater significantly affects the cyclic behaviors of rocks in general. However, the water pressure has a negligible effect. Source

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