| Based on the prototype of single-line unballasted track railway embankment, shaking table model tests of 4 types of compaction embankments and 2 patterns of reinforced embankments were designed and carried out. Numerical models of embankments were established and the main shaking table test conditions were simulated. A series of laboratory tests on mechanical properties and seismic behaviors of new patterns of reinforced earth structures including reinforced gabion retaining wall, green reinforced gabion retaining wall, and geogrid reinforced earth retaining wall of flexible wall face were widely carried out. Horizontal slices analysis method was adopted to deduce seismic earth pressure formulas to compensate the shortcomings of Mononobe-Okabe formula which was widely used in current seismic codes. The main researches can be concluded as follows:(1) Shaking table model tests of embankments with compactions of 95%,93%,90% and 87%, and reinforced embankments with 2-layer or 4-layer reinforcements were designed. According to similarity theory, the similarity relations of main physical quantities for shaking table model tests were deduced, and simulation materials were selected. Large-scale triaxial tests and other routine soil tests were carried out and the main physical and mechanical properties of filler were obtained.(2) Taking the shaking table test results of embankment with compaction of 95% as example, dynamic characteristics of embankment and their influencing factors were analyzed. The behaviors of horizontal acceleration response, vertical acceleration response, seismic earth pressure response, and dynamic displacement response under different intense excitations of different seismic waves were studied. The factors which influenced horizontal and vertical acceleration magnification were analyzed including the types of seismic waves, the intensity of excitation, multi-directional input, time compression ratio, etc. Combined with the dynamic characteristics of embankment, seismic wave propagation characteristics were studied by time domain analysis and frequency domain analysis. Seismic settlement and lateral residual deformation of embankment were measured, and the distributions of residual deformation were obtained. Numerical model was established by FLAC3D based on shaking table test model, and the major loading conditions of shaking table test were simulated. Numerical simulation results could be taken as a supplement or verification for shaking table test.(3) Shaking table model tests of embankments with compactions of 95%,93%,90% and 87%, and reinforced embankments with 2-layer or 4-layer reinforcements were carried out. Dynamic parameters of different types of compaction embankments and different patterns of reinforced embankments were obtained, and the dynamic characteristics and their influencing factors were analyzed and compared. The differences of horizontal and vertical acceleration magnification distribution among different types of compaction embankments and different patterns of reinforced embankments were analyzed. The behaviors of the dynamic earth pressure response, dynamic displacement response, seismic settlement and lateral residual deformation of different types of compaction embankments and different patterns of reinforced embankments were compared. And the influencing factors such as the compaction of filler, the reinforced forms of embankments were analyzed. Meanwhile, numerical models were established by FLAC3D based on shaking table test models of different types compaction embankments and different patterns of reinforced embankments, and the major loading conditions of shaking table test were simulated. Numerical simulation results were compared with shaking table model test results.(4) Tensile mechanical properties of different reinforcements were studied and compared according to the tensile tests. With red sandstone as filler, pull out tests of gabion meshes and geogrid were carried out. By applying cyclic loading and unloading of different magnitudes at the top of retaining wall, bearing capacity behaviors of reinforced gabion retaining wall, green reinforced gabion retaining wall and geogrid reinforced earth retaining wall of flexible wall face were studied. By applying dynamic load of different amplitudes and frequencies, dynamic deformation behaviors of these three new patterns of reinforced earth structures were studied. By applying different intense horizontal excitations of different seismic waves, the seismic behaviors of new patterns of reinforced earth structures were studied. Test results showed that the new patterns of reinforced earth structures, as flexible structures with excellent structural measures, could consume lots of seismic energy and presented good deformation behaviors even under strong seismic excitations.(5) Based on planar rupture surface assumption of Mononobe-Okabe theory, horizontal slices analysis method was adopted to deduce analytical formulas of resultant force of active and passive earth pressure, application position of resultant force and distribution of seismic earth pressure. The explicit solutions of critical rupture angles both for active and passive earth pressure were obtained by graphic method. And iterative method for crack depth calculation of active earth pressure was proposed. The influencing factors were considered in formulas such as horizontal and vertical seismic acceleration, batter angle of wall back, cohesion and internal friction of filler, cohesive force and external friction angle between filler and the back of retaining wall, equispaced overloading, etc. And parameters analysis was made on these factors. It was shown that the formulas were the same as the existing active and passive earth pressure formulas under corresponding simplified assumptions. The formulas were also proved reliable and valid by examples.(6) According to the active and passive earth pressure formulas under seismic condition deduced by horizontal sliced analysis method, calculation program was designed by Visual Basic 6.0. |
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