Settlement Regularity And Control Technology Research Of Ultra Thick Backfill Subgrade In High Speed Railway Tunnel Under The Condition Of Giant Karst

The high-speed railway tunnel through karst giant,the scheme of subgrade filling treatment is reasonable,and the construction technology is simple and cost-effective,but the ultra thick backfill settlement problem is the key problem of restricting the implementation of the plan.If the subgrade settlement is too large after the completion of construction,it will appear uneven pavement and influence the speed of the train,which will endanger the safety of the train.Based on the research of predecessors see,relying on the new-bulit Qian Zhang Chang high speed railway of the Gaoshan Tunnel through the giant karst cave across segment super thick backfill subgrade project,to the settlement regularity and control technology,by means of geological survey,theoretical analysis,numerical simulation and remote online monitoring combination,carried out the following aspects of the research work:The three aspects of stability monitoring of karst caves,such as UAV detection,3D laser scanning technology and blasting vibration,has been carried out in tunnel blasting and ultra thick backfill construction.The research shows that: There are many dangerous rock masses around the cave,which are complex in shape and poor in overall stability.The safety allowable value of the blasting vibration velocity of the rock mass on the surface of the karst cave is 1cm/s,and the falling stone will occur if it is beyond during the blasting excavation of the main tunnel.The monitoring results will provide substantial guidance for tunnel excavation and cave filling construction.In accordance with the settlement monitoring requirements in the technical regulations of the high speed railway subgrade engineering(Q/CR9602-2015),the settlement of super thick backfill in the mega karst cave Subgrade in high mountain tunnel is monitored by remote on-line monitoring.The monitoring items including surface subsidence,stratified settlement,horizontal displacement of Subgrade and the bottom of the base plate,it obtains the relationship of the change of settlement and the related original data,and analyzes the road.The settlement regularity of super thick backfill body provides a basis for further establishment of settlement prediction model.The curve regression method is used to analyze and predict the settlement curve of the super thick backfill in the tunnel of high mountain tunnel,and the reasonable settlement deformation trend is determined,and the prediction reliability is analyzed.The finite element numerical simulation program is used to simulate the construction settlement of the main line Subgrade of the tunnel.The simulation shows that:the settlement difference of the super thick Subgrade along the longitudinal section is obvious,the whole settlement appears in the middle and the small ends,at the same time there is a local trend of the large mileage end settlement greater than the small mileage end,which is consistent with the conclusion obtained from the actual monitoring;the numerical simulation of the structure load of the tunnel is applied,and the calculated results of the monitoring point two are compared with the fitting values of the exponential curve model,and the simulation values are in agreement with the fitting values,and the correctness of the model is proved at the same time.The feasibility of exponential curve for settlement prediction under this geological condition is explained.In view of the settlement overrun problem that in the super thick backfill Subgrade often occurs after construction.Based on overrun control the grouting technology and structural system of self-adjustment technology are put forward under the premise of ensuring the 50 cm clearance of tunnel lining.This technical measure is of great reference value for similar super thick backfilling subgrade engineering.The new-built Qian Zhang Chang railway of Gaoshan tunnel is the first tunnel crossing 100 meters of karst cave in China.The thickness of the backfill is more than 50 m.Therefore,the research of the roadbed settlement regularity and settlement control technology is of great significance,and is of great reference significance to other similar giant karst treatment.