Experimental Study On The Processing Technology Of Soil Compaction Pile In Collapsible Loess Foundation In High Speed Railway Station

High-speed railway buil non-ballasted track construction, which requires strictly to subgrade stability and residual control settlement. To meet the strict requirements of the high-speed rail in the loess region train, which at load uneven settlement, cumulative settlement and line the overall stability. The foundation or subgrade treatment, the treatment process also has more stringent requirements.Collapsible loess is a kind of unsaturated undervoltage consolidated soil which has large pore and vertical joints. Under the natural moisture, it has low compressibility, high strength, but under certain pressure of flooding, its structure is destroyd rapidly, and generates significant additional deformation, all of these are great harm to the engineering. Therefore, the construction in collapsible loess region should be based on the characteristics of collapsible loess and engineering requirements to deal with the foundation, in order to make the soil within the scope to increase dry density, improve the bearing capacity, lower permeability, eliminate wet sex, improve soil physical and mechanical properties. Commonly used processing methods mainly include:cushion method, compaction method, compaction method, the reinforcement method and chemical immersion method.This article is based on principle of composite foundation of cement-soil compaction pile method, mechanism and effect of reinforcement. Reinforcement mechanism is based on the lateral compaction of soil between piles and pile body displacement function. The foundation soil pipe weeks get greatly horizontal compression when the pile driver throws the casing into the formation, to make the surrounding soils compacted; then good mixing cement-soil is layered to backfill to compaction pile hole and uses the rammer ramming the stratification to make certain strength of pile body and the compaction of soil between piles. This method of foundation reinforcement treatment has good effect, fast construction, low engineering cost, so it is widely used in collapsible loess foundation treatment of the passenger railway station floor. Under certain conditions this method has the good economic efficiency and broad prospects for development.This article is based on a culvert of collapsible loess foundation for project which located in the new treasure special passenger hub in Lanzhou west railway station, the range of layer is mainly of Quaternary Holocene alluvial sandy loess, the thickness is from10meters to20meters, the collapse type field is self-respect, wet rating is class Ⅱ, wet soil thickness is about8meters. Paper adopts the method of combining experimental research and theoretical calculation to study collapsible loess foundation treatment technology of the high speed railway station.First of all, through indoor and field test of natural loess foundation physical and mechanical properties test, we know the physical and mechanical properties and engineering use characteristics of the collapsible loess in test site; Second, based on the summarize of the current level and practical application of the cement soil compaction pile, analyze which aspects of the reinforcement,design and construction technology of mechanis need to be improved and perfect; Then, based on actual loess foundation treatment in the experimental site, test the foundation treatment effect; Finally, through the field of composite foundation of small load immersion test, determine the treatment effect according to the design parameters of the composite foundation, evaluate the collapsible loess foundation treatment parameters in the high-speed railway station to guide the similar engineering practice.Indoor test results show that:modulus,degree of compaction and permeability of soil between piles are better than that of the undisturbed soil; The degree of compaction of cement-soil pile is far greater than that of the undisturbed soil, the unconfined compressive strength increases with the growth of the age.Field test results show that:single pile bearing capacity characteristic value of cement-soil compaction piles (450kpa to600kpa) and composite foundation bearing capacity characteristic value (300kpa) have greatly improved compared with that of natural foundation bearing capacity (150kpa); Additional subsidence caused by flooding pressure of200kpa is9millimetres and collapsibility is basically eliminated, infiltration only happen in the surface of pile, soil between piles is given priority to vertical infiltration, vertical infiltration depth can be up to4meters,and that of horizontal infiltration ranges within2meters.