无锡某地基埋藏型岩溶发育特征及充填物来源

Development characteristics of buried karst under a foundation in Wuxi and sources of karst fillings

研究埋藏型岩溶的发育特征和充填物来源对拟建超高层建筑的选址及持力层的选择具有重要意义。本文通过跨孔地震CT对溶洞和破碎带进行探测,并对部分代表性溶洞的充填物进行比重试验、颗粒分析和X射线衍射分析,结合现场工程地质情况,研究了距地表以下80余米处岩溶的规模、分布情况、岩溶发育特征及溶洞充填物来源。结果表明:溶洞发育规模较小,面积多在2m2以下,在垂直方向具有多层性;溶洞充填率达到92.7%,多为硬塑泥质全充填,承载力较大,可作为基础持力层;溶洞填充物的矿物成分基本相同,且与上覆基岩一致,充填物来源主要为上覆基岩的剥蚀;溶洞之间不存在大的连通通道,且地下水位已降至场地溶洞以下,故该处溶洞不会进一步发育,不会对上部地基稳定性造成威胁。

The development characteristics of burial karst and sources of the karst fillings are very important for choosing the location of super-high buildings and bearing strata.This study employed the cross-hole seismic CT method to detect the caves and fracture zones of a foundation in Wuxi,and made indoor tests on samples of the karst fillings from the typical karst caves.Combined with the in-situ geological conditions,this paper presents a qualitative analysis of the scale,distribution and development characteristics of the karst and the sources of fillings which are more than 80 meters below the foundation.The results show that the karst is of a small size,the area of most caves is less than 2m^2,and there are many layers in the vertical direction.The rate of cave filling reaches 92.7%,and the caves are mostly filled with hard plastic mud which has a large bearing capacity and can be used as the bearing layer of foundation.XRD analysis of mineral composition shows that the minerals of different cave fillings are generally the same,consistent with those of the overlying bedrock.Thus,the denudation of overlying bedrock is the main source of these fillings.There is no large connective channel between the caves,and the underground water level has dropped below the caves.It is therefore concluded that these caves will not further develop and pose no threat to the stability of the foundation.The results of this study will provide reference for the site selection,design and construction of super-high buildings,karst detection,stability analysis of foundations and the treatment of unfavorable geological bodies in the Suzhou-Wuxi-Changzhou areas,which are located on deep karst foundation.