西南地区某边坡工程事故原因分析

Cause analysis of a certain slope accident in southwest of China

为查清西南地区某边坡工程抗滑桩倾倒的原因,在设计计算复核的基础上,现场重点对抗滑桩嵌固段的岩土工程性状进行核验,同时对边坡工程施工质量进行抽检。采用地质钻探和取样重构地层剖面、重型动力触探试验确定嵌固段土层的力学参数。采用低应变和钻芯法确定抗滑桩桩身完整性、桩长、桩身混凝土强度;使用探井法核验桩身是否被折断。对比分析原勘察报告和核验资料在嵌固段岩土工程性状上的差异,采用核验获得的岩土力学参数重新对设计计算进行复核并考虑相关施工质量缺陷。综合分析确定该边坡工程事故主要原因是勘察未对出现的玄武岩划分风化程度和层厚、未提供设计所需的比例系数等岩土力学参数和设计计算有误,设计采用了非勘察报告提供的岩土力学参数;次要原因是桩后填土填料及填筑质量不满足设计要求以及桩后地表未设置完整的截排水系统。

On the basis of design accounting,the geotechnical mechanics characters of the embedded pile are verified,and the construction quality of the slope is inspected in order to find out the cause of toppling down of the anti-slide pile slope accident in southwest of China. Drilling and sampling are used to reconstruct the stratigraphic profile,heavy dynamic penetration test are used to determine the geotechnical parameters of embedded soil. The integrity and length of the pile are determined by low strain method,the concrete strength of pile body are determined by core drilling,and whether the pile is broken is checked by exploration well method. The cause of the accident is analyzed by comparing the difference of the geotechnical parameters between old investigation report and new verified data,accounting design calculation with new verified parameters and considering quality defection. The comprehensive analysis shows that the main cause due to the investigation report which does not provide weathering degree and thickness of the basalt and enough geotechnical parameters for design. Also the wrong design calculation which does not use the parameters provided in investigation report is the main cause. The secondary cause is the filling soil and filling quality behind anti-slide pile cannot satisfy the design requirement,and drainage system is not complete. The results can provide a reference for further anti-slide pile engineering.