Study On Stability Of Karst Subgrade Of High-speed Railway And Application Of Grouting Treatment

In recent years,the construction of high-speed railway has gradually become difficult to meet people’s travel needs,so it is necessary to speed up the construction of high-speed railway.However,in real life,it is almost impossible to avoid the unfavorable geological areas,including karst geological areas.For the high-speed trains,the high smoothness and stability are important,at the same time,it is also important to maintain high speed.Therefore,it is significant to study the causes,damage mechanism,treatments and effect detection techniques of the diseases in karst areas.This thesis mainly studies the following aspects:(1)On the one hand,this paper analyzes and studies the karst diseases,collapse reasons and stability failure of foundation.On the other hand,the model simulation and analysis of subgrade karst disease in the DK59+989-DK60+943 section of Weilai High-speed Railway Passenger Dedicated Line shows that grouting can effectively promote the stability of foundation,and various effect detection technologies can analyze the geological conditions before and after grouting in detail,which provides a theoretical basis for practical application.(2)According to the analysis of the stability of subgrade under the train load through the ANSYS two-dimensional numerical model,it shows that with the deepening of karst cave,the vertical settlement displacement caused by train operation gradually decreases displaces from33.7mm to 31.6mm,and the slowing trend is gradually stable.It shows that the karst cave is more closer to the subgrade,the influence of karst cave gap is more greater on subgrade deformation and the subgrade is more unstable.With the increase of karst cave diameter,the vertical settlement displacement caused by train running gradually increases from 12.295 mm to 37.7 mm.And the stability of roadbed becomes worse with the increase of karst cave diameter,which shows that the absolute size of karst cave diameter affects the stability of foundation.(3)Through model simulation,it is found that the maximum vertical settlement displacement of karst cave after grouting treatment is 11.998 mm in S10,which meets the settlement requirement of high-speed railway of no more than 15 mm.The area above the karst cave is easy to collapse,and the settlement deformation in this area is also slowed down,which enhances the stability of the subgrade superstructure.(4)Grouting makes the gap of karst cave be fully filled,and makes the karst cave and foundation become an entirety.In this research,the karst grouting design,the optimization of grouting reinforcement scope,grouting hole layout,grouting equipment and grouting pressure of the section DK59+989-DK60+943 in Weilai High-speed Railway Passenger Dedicated Line are analyzed.And based on the field investigation and analysis of research sites,the construction technology of field test section is introduced in detail,including drilling,hole cleaning,grouting,hole sealing and so on.The key points of quality control and some special treatment in grouting process are put forward.In addition,four detection methods,namely transient surface wave method,high-density resistivity sounding method,drilling coring method and water pressure test method,are used to compare and analyze karst foundation before and after grouting,which can make the detection results better and more accurate.