强夯法处理黄土地基的效果评价及沉降分析

Evaluation and Settlement Analysis of Collapsible Loess Soils Improved by Dynamic Compaction

基于对宁夏东部地区某工程场地夯实处理后的地基进行详细的勘察与检测,分别采用室内土工试验、标准贯入试验、重型动力触探试验和堆载试验的方法,对黄土地基的夯实处理效果进行评价,对可能引起场区内地基沉降的因素进行分析,结果表明:(1)经过强夯处理的黄土地基密实度高,压缩性低,强夯面以下的表层黄土状粉土的湿陷性已基本消除,地基土承载力达到设计要求,强夯法对宁东地区黄土地基的适用性较高;(2)对于地基表层存在黄土状填土的地基,在基础施工期前应在地表设置一定厚度的灰土垫层,以消除不均匀浸水时产生轻微的沉降差,且宜选用底部碎石土层作为天然地基基础的持力层;(3)填土的固结沉降、湿陷以及遇水软化现象均会导致黄土地基的沉陷,其本质原因是黄土地基原有结构产生了破坏。研究成果对宁东地区黄土地基的设计处理具有一定的借鉴意义。

This paper presents the geotechnical engineering investigation and evaluation results of a collapsible loess project site in the east Ningxia before and after the soil improvement by the dynamic compaction.The investigation methods included laboratory soil tests,standard penetration tests,Becker penetration tests as well as in-situ plate loading tests before and after the soil improvement.The settlement of the site was also evaluated.The following results can be obtained：1）the unit weight of the loess soils was significantly increased.The compressibility of the loess soil was low and the collapsible potential of the surficial loess soils were reasonably eliminated.The bearing capacity of the improved loess soils reached the design requirements.The dynamic compaction was suitable for improving the east Ningxia loess soils.2）for sites that were backfilled with collapsible loess soils,a layer of cushion material is necessary at the bottom of the foundation so that the minor settlement induced by the surface water infiltration could be avoided.Gravel is the desired cushion material.3）The consolidation induced by the backfill material and soaking of the collapsible loess filling material could also induce settlement in loess soils.