兰新客运专线戈壁路基CFG桩加固试验研究

Experimental Study of Using CFG Columns Improving Subgrade of Lanxin Passenger Rail Line in Gobi Desert

为探讨CFG桩在戈壁铁路路基中的工程特性,分析其加固效果,进行了小应变、钻芯取样、单桩承载力试验检测成桩质量,采取复合地基承载力、沉降观测等试验研究加固效果,采取不同的桩间距研究间距对桩复合地基承载力的影响,该试验为指导后期建设和戈壁地区路基加固处理提供了经验。试验结果表明:①戈壁土地层对CFG桩施工质量无不良影响,被检测桩合格率为98.5%;②长螺旋泵送混凝土CFG桩工艺适用于戈壁土地层,桩身芯样强度完全满足设计要求;复合地基承载力能够满足设计要求,③CFG桩在戈壁路基中的合理桩间距为1.5m,当桩间间距超过1.5m时,其复合地基承载力与设计承载力相差较大。④工后的沉降量小,沉降稳定时间短。

To evaluate the effect of the proposed soil improvement, a series of tests has been performed on CementFly ash Gravel （CFG） columns in the Gobi Desert of a rail road subgrade improvement project. These tests are： small strain integrity tests; coring through the CFG columns axial loading tests on single column as well as column groups and settlement observa tions. The impact of the column spacing on the bearing capacity of the composite ground is studied. The objective of these tests and studies are for the later phase constructions and providing experience of subgrade improvement of railway in the Gobi Des ert. The test results show： 1） Gobi soils have no obvious adverse effect on the quality of the CFG columns. Based on the integ rity test results, a high acceptance ratio of 98.5% is observed. 2） Pumping concrete through a long distance using spiral pum ping method is an appropriate technique for the CFG column installation. This has been verified through the sample cores from the installed columns. 3） The optimum column spacing in the Gobi Desert is 1.5 meter. When the spacing exceeds 1.5 m, a larger variation of composite capacity between the design and tested values are observed. 4） The composite ground has a small post construction settlement and a short duration for settlement stabilization is necessary.