Study On The Design Of Retaining Structure With Double-row Piles Considering The Soil Arching Effect And Its Engineering Application

The double-row pile retaining system (DRPRS) is a new structure style forretaining the deep excavation applied firstly in eighty decade of twenty century. It is agate like spatial retaining system formulated by installing two rows of parallel pilesand combining the front and the back piles at the pile top using plates or beams.DRPRS can control the deflection of deep excavation effectively due to its excellentanti-moving stiffness. Comparing with traditional retaining structures such asanchored or single-row cantilever piles, it works well in terms of the pile internalforce and the displacement that is much smaller than that of others, and is capable ofadapting complex and varied loading conditions. Despite of these above merits, thereare some valuable issues about DRPRS demanding more investigation, especially theproblem relating to the earth pressure acting on the front and back piles, and thatinvolving the influence of pile-soil interaction on the stability of the retainingstructure. Excavation protecting engineering is usually temporary and need nopost-construction function. Hence, it has a great theoretical and practical significanceto investigate the development and distribution mechanism of the earth pressure, andconduct all possible optimal design considering varied influence factors given thesatisfaction of the safety and stability of the deep excavation, in the calculationprocess of designing DRPRS.This present work firstly summarized the available calculation theories andmethods of DRPRS that were usually used in the routine design, and discussed theirapplicability and deficiency respectively. Based on it, the arching mechanism of soilsbetween the piles and behind the piles in the excavation process and after theexcavation were investigated respectively, along with the mechanical characteristicanalysis for the arch of the deformed soils. Assuming that the wall surface wasvertical, smooth and parallel, the mechanical analytical model of soil arch wasestablished to analyze the generation of the middle and small principal stress arches,and to formulate the computing formulas of lateral earth pressure of DRPRS based onthe soil arching effect. The later earth pressure coefficients under both circumstancesof using soil arch of the circular shape and the catenary’s line, with the wall-soilfriction fully mobilized and partially mobilized, were calculated by Matlabprocedures. The comparative analysis between the distributions of earth pressure forthe two circumstances was conducted subsequently. Combining with a case history, the proposed calculation method for DRPRS herein was used to give its structuredesign and the stability check and its economy and engineering practical significancewas verified through the comparative analysis of the calculated results with the resultscomputed by LiZheng Deep Excavation6.0that is the most usually used designingcommercial software in routine design in China. Additionally, the comparativecalculation analysis with respect to the relevant designing parameters of DRPRS wereconducted and resulted in the influence variation of row space, the crossing sectiondimension, the stiffness of the linking beam and other parameters on the internalforces and displacement of DRPRS.