高铁站场PHC桩和CFG桩复合地基工程力学特性分析

Analysis for Engineering Mechanical Characteristics of Composite Foundations for PHC and CFG Piles of High-speed Rail Stations

对高铁站场咽喉区深厚软土大面积堆载预压下复合地基的工程力学与变形特性开展现场试验研究,分析不同位置和深度的超孔隙水压力、沉降变形以及桩土应力等参数随时间和填土高度的变化规律。研究结果表明:1)高铁站场咽喉区复合地基内的超孔隙水压力随着荷载增加而增大,达到峰值后,随时间延长而逐渐消散,其变化略滞后于荷载的变化;超孔隙水压力的最大值出现在下卧层上部,此处附加应力也较大;在下卧层中,随着深度增加,超孔隙水压力逐渐减小。2)高铁站场咽喉区复合地基由路堤中心向外,桩应力、桩间土应力及桩土应力比总体呈减小趋势。在路堤填筑和预压中,站场咽喉区复合地基桩间土应力向桩传递,桩间土应力逐渐减少,桩顶应力逐渐增大,并逐渐趋于稳定。

This paper develops on-site experimental research on engineering mechanical and deformation characteristics of composite foundations under large-area preloading of deep and thick soft soil in throat area of high-speed railway stations, and analyzes change rules of parameters such as excess pore water pressure, sedimentation deformation and pile-soil stress, etc. with time and depth of fill so as to provide a scientific basis for design and construction of similar projects. The results of research show that：1 ） The excess pore water pressure in composite foundations in throat area of high-speed railway stations increases with load, and dissipates gradually with prolonged time, and its change slightly lags behind change of load;the maximum value of excess pore water pressure appears on the top of underlying stratum where additional stress is also large; in underlying stratum excess pore water pressure decreases gradually with increase of depth. 2 ） In composite foundations in throat area of high-speed railway stations, from the center of embankment to outside pile stress, soil stress between piles and pile-soil stress ratio shows a tendency of decrease in general. In fill and preloading of embankment, the soil stress between piles in composite foundations in throat area of stations transfers to piles and decreases gradually, and the stress on the top of piles increases and tends towards stability gradually.