Study On Arching Mechanism Of Mudstone Base In Deep Cutting Of High Speed Railway In Cheng-Yu Region

Because of the widespread use of ballastless tracks on the high-speed railway,there is a strict requirement to the control of deformation of arch on subgrade.In recent years,a number of high-speed railways in Cheng-Yu region of China have experienced serious arch deformation in the construction of deep cutting sections,affecting the normal operation of the railway.Therefore,it is of great significance for controlling and preventing the problem of swelling deformation of high-speed railways to study the mechanism of subgrade swelling and establish its numerical model.In this thesis,two swelling segments of Cheng-Yu passenger transport line are taken as the study area to conduct research on the mechanism of the subgrade swelling of high-speed railway deep excavation cutting and make analysis on the swelling deformation law,stress and strain variation characteristics of the cutting subgrade by adopting the research methods of field geological survey,laboratory test and numerical simulation.The major research work of this thesis is as follows:(1)By means of data collection and field investigation,the topography,lithology,geological structure and hydrogeological characteristics of the study area are identified,and the deformation characteristics of the subgrade arch and the causes of the basement arch in the study area are analyzed through the monitoring data of the subgrade arch and the measured ground stress data.(2)Through the uniaxial compressive strength experiment of rock,the failure characteristics of mudstone under natural moisture content and saturated moisture content are studied and the strength parameters are obtained;through the expansion test of mudstone,the expansion force,free expansion force and saturated water content of mudstone are measured,and the expansion deformation curve of mudstone is obtained to study the expansion deformation characteristics of mudstone.(3)Through the uniaxial unconfined creep test of mudstone under different water conditions,the deformation characteristics of mudstone under the combined action of expansion and creep are studied,and the constitutive model describing the expansion and creep deformation of mudstone is established.Based on the above tests,the expansion characteristics and creep characteristics of mudstone in the study area are summarized to provide the basis and parameters for establishing the numerical model.(4)The elastic-plastic and rheological simulation of the cutting in the study area was carried out by numerical simulation software FLAC3 D,and the stress and strain distribution characteristics of the cutting and the deformation characteristics of the upper arch were analyzed.Through the establishment of a simplified model,the influence of three factors,namely,the structural form of the cutting,the thickness ratio of the sand-mud rock layer and the stratum dip angle,on the arch amount on the subgrade is simulated.The above research provides the basis for the governance and maintenance of the subgrade arch of Cheng-Yu passenger dedicated line,and provides reference for the construction of high-speed railway in Cheng-Yu region.