摘要
岩溶区桩基施工时,钻孔常钻穿溶洞顶板导致泥浆面突然下降而引起地面塌陷,但其机制尚不十分清楚。将PIV技术与模型试验相结合,安装百分表测试地面沉降,在模型箱正面安装高清数码摄像机采集影像,利用GeoPIV程序处理照片,得到应变云图、位移矢量图,揭示溶洞上覆土层特征、钻孔直径对地面沉陷的影响规律,为岩溶区桩基施工方案决策提供依据。结果表明:(1)溶洞顶板钻穿后,地面最终沉降、沉陷规模和深部土体破坏程度随溶洞顶板上部砂土层厚度的增大而增大,随黏土层厚度的增大而减小;地面沉降的响应时间随黏土层厚度的增大而延迟,随砂土层厚度或钻孔直径的增大而缩短。(2)地面最终沉降、土体下沉范围随钻孔直径增大而增加,沉陷历时随钻孔直径增加而减小。(3)溶洞顶板钻穿后,上覆土层约60 s内受诱发而移动,地面沉陷具有突发性;地面沉降发展经历响应累积、快速下沉、缓慢下沉、稳定4个阶段。(4)上部黏土层、下部砂土层的地质条件下,溶洞顶板钻穿后土体渐进破坏过程为,泥浆顶面下沉到砂土层一定深度以后,砂土向溶洞内滑移下陷;当砂土顶面倾角接近砂土内摩擦角时,砂土停止滑动;黏土土拱形成以后,地面恢复稳定。(5)工程中,如果溶洞顶板上覆土层主要为无黏性土,或者下层无黏性土与上层黏性土厚度比超过1.35,建议采用注浆法加固无黏性土层,预防地面塌陷。
In the construction of pile foundation in karst area,drilling through the cavity roof often leads to the ground collapse induced by the downward movement of mud,but the mechanism is not well understood.In this paper,the PIV technology was combined with the indoor model test,the dialgauge was installed to test ground settlement,the high-definition digital camera was installed on the front of the model box to capture images,the GeoPIV program was used to process the photos and obtain strain cloud maps and displacement vector maps,the influence law of the characteristic of overlying soil layer of cavity and the diameter of drilled hole on the ground collapse deformation of drilled hole was revealed,which provides the decision basis for the construction plan of pile foundation in karst area.The results show that:①After drilling through the cavern roof,the final ground settlement,collapse scale and deep soil damage degree increase with the increase of the thickness of sandy soil layer and decrease with the increase of the thickness of clay layer on the cavern roof.The response time of ground settlement is delayed with the increase of clay layer thickness,and shortened with the increase of sand layer thickness or borehole diameter.②The final settlement of the ground and the sinking range of the soil increase with the increase of the diameter,of drilled hole and the collapse time decreases with the increase of the diameter-length ratio.③After drilling through the top plate of the cavity,the overlying soil layer is induced to move within 60 seconds,the ground collapse is sudden.The development of ground subsidence goes through 4 stages,such as response accumulation,rapid sinking,slow sinking and stabilization.④Under the geological conditions of upper clay and lower sandy soil,the process of progressive damage of the soil after the uncovering of the cave roof is as follows:after the top surface of the mud sinks to a certain depth of the sandy soil layer the sandy soil undergoes self-weight stress to slip and sink into the cave.When the dip angle of the top surface of the sand is about equal to the internal friction angle of the sand,the sliding stops.After the formation of the clay soil arch,the ground restores stability.⑤In the project,if the overlying soil layer of the cavern ceiling is mainly non-cohesive soil layer,or the thickness ratio of the lower non-cohesive soil layer to the upper cohesive layer exceeds 1.35,it is recommended to reinforce the upper part by grouting to prevent the ground from collapsing.
作者
周德泉
谢瑞庭
曹勇
高祁
刘海龙
刘宏利
ZHOU De-quan;XIE Rui-ting;CAO Yong;GAO Qi;LIU Hai-long;LIU Hong-li(School of Civil and Environmental Engineering,Changsha University of Science&Technology,Changsha 410114,Hunan,China;The 6th Engineering Company of CCCC Fourth Harbor Engineering Co.Ltd.,Zhuhai 519000,Guangdong,China;China Road&Bridge Corporation,Beijing 100011,China)
出处
《中国公路学报》
北大核心
2026年第1期200-211,共12页
China Journal of Highway and Transport
基金
国家自然科学基金项目(52278329)
湖南省交通运输厅科技项目(202019,202247)
湖南省研究生科研创新项目(CX20210765,CX20210774)。
关键词
路基工程
岩溶塌陷
模型试验
PIV
渐进破坏
subgrade engineering
karst collapse
model test
PIV
progressive damage
