Research On The Settlement Control Technology Of A High Speed Railway Subgrade In Loess Area

Yin(Chuan)Xi(An)high~speed raiyway Yin(Chuan)Wu(Zhong)section(for short YinWu highspeed railway)is a ballast high-speed railway in counstrction.Infulenced by the construction period and bridge construction,subgrade stack preloading measures can not be taken.IN order to control the settlement,we need to strengthen the roadbed.Based on the construction reality? investigation and researching,the options about the reinforcement measures of the yin wu high-speed raiyway are given.Through the numerical analysis,the settlement characters and stress characters of YinWu high-speed railway are analyzed.Through the field test field monitoring,the foundation trement mesures bearing and foundation settlement rules are analyzed.The main research contents and conclusions are as follows.(1)By investigating the landform,engineering geology,climate and rainfall along the raiyway.it shows yinwu railway is desigended in the yellow river alluvial plain area or the yellow river terraces trailing edge piedmont.the silt sand and soft soil is spread on the surface of the yellow river alluvial plain,which the thick round is under them.The yinwu railway constructed area's rainfall are smalle,but rain will concentrate in summer and autumn.Rain will seep into and softening the subgrade soil,cause roadbed subsidence and other rodbead disease.(2)As to impaction and grind method in origin design,based on the counstraction reality and engineering geology,the dynamic compaction measures are adopted.Paving the geocell under the YinWu raiyway's bed bott will be adopted,the following Settings in the surface layer of subgrade bed two cloth a membrane.(3)A numerical model analysis is performed on the typical cross section of subgrade.In subgrade settlement,the subsidence at the center of the subgrade is larger and the subsidence at the foot of the subgrade is smaller,forming a subsidence basin;the pile-soil stress ratio decreases from the center of the subgrade to the foot of the slope;Room reinforcement measures can reduce the vertical settlement of the foundation.According to different factors,it can be seen that,with different cushion reinforcement methods,the geotechnical cells have the smallest amount of reinforced settlement and the maximum pile-soil stress ratio;for different filling heights,the higher the filling height is,the larger the settlement is,but for piles and soils.The stress ratio has no effect;for different pile spacings,the smaller the pile spacing,the smaller the vertical settlement of the foundation and the smaller the pile-soil stress ratio.(4)The half screw pile construction technology and construction methods are put forward.excavation test shows that half screw piles are of good quality.(5)The bearing capacity of the composite foundation obtained from the static load test agrees well with the calculation result.The characteristic value of the bearing capacity of the single pile is greater than 620 kN.For the foundation treatment of the foundation treatment of dynamic compaction,the development of the subsidence settlement is slow;the subgrade settlement of the subgrade in the foundation treatment of the screw pile is mainly developed during the period of filling and transporting the beam,and the development is slow in the later period;the settlement of the foudation has been effectively controlled.