高速铁路泥岩地基原位浸水响应特征试验研究

Experimental Study on In-situ Flooding Response Characteristics of Mudstone Foundation for High-speed Railway

随着我国高速铁路飞速发展,将涌现出大量以弱膨胀性泥岩为地基的高速铁路工程。由于高速铁路无砟轨道对路基变形要求极为严格,而弱膨胀性泥岩地基引起的高速铁路路基上拱研究鲜有报道,通过人工浸水方式在兰新高速铁路的路基上拱地段开展不同上覆荷载下弱膨胀性地基泥岩现场原位浸水试验,分别研究0、15、30、45 kPa 4种上覆荷载下泥岩横向渗透速率及竖向膨胀量。试验研究结果表明:泥岩浸水时横向体积含水率表现为稳定、骤增、减速增长和渗流稳定四个阶段;同一横向位置处,下部土体渗透稳定含水率大于上部土体;膨胀量随浸水量呈“S”型变化,且上覆荷载较大时会出现下沉现象;横向渗透速率随上覆荷载增加而减小,且横向渗透速率与横向渗透距离为非线性关系;提出以横向相对渗透衰减率100%作为控制标准确定高速铁路路基上拱临界荷载的设计思路。

A large number of high-speed railway projects with weak expansive mudstone foundation will emerge with the rapid development of China’s high-speed railway.The ballastless track of high-speed railway has strict requirements for subgrade deformation.The arching of high-speed railway subgrade caused by weakly expansive mudstone foundation is hardly reported.The in-situ soaking test of the mudstone in the weakly expansive foundation under different overlying loads was carried out in the upper arch section of Lanxin High-speed Railway by artificial flooding.The lateral permeability and vertical expansion of mudstone under four overlying loads of 0,15,30,and 45 kPa were studied.The results of the tests show that the lateral volumetric water content of mudstone immersion shows four stages of stability,sudden increase,deceleration growth and seepage stability.The permeability and stable water content of the lower soil is greater than that of the upper soil mass at the same lateral position.The amount of expansion changes with the amount of water immersion in the“S”shape,and the subsidence occurs at large overburden load.The transverse permeation rate decreases with the increase of overburden load,with the transverse permeation rate being nonlinear with the lateral permeation distance.The design idea of determining the critical load of the arch on the high-speed railway subgrade with the horizontal relative permeability attenuation rate of 100%as the control standard is proposed.