Application of high-density resistivity method and audio-frequency magnetotelluric method in the detection of landslide structure in Houchang town

LIU Yongliang; ZHANG Wei; LIU Zhenyu; YI Lianxing; WU Qiuju; LIANG Nan; GAN Fuping; WU Jianqiang; HAN Kai

doi:10.11932/karst20240208

Abstract：The frequent occurrence of landslides in China has done great harm to people's lives and property.In the stability analysis of landslides and the design of treatment scheme,the application of geophysical technologies has become a frontier research field in engineering and environment in terms of interdisciplinary development and application.The Houchang landslide in Weining county,Bijie City,Guizhou Province is a typical karst landslide.The landslide area is dominated by karst peak-cluster depressions or gullies,in which limestone strata are widely distributed,and karst is strongly developed.Since the collapse and landslide in 2006,the scale of tensile cracks in rock mass has gradually increased.In order to explore the causes of collapse,scholars have deduced the collapse process,established the conceptual model of landslide and studied the karst hydrogeological conditions.However,due to the lack of detection data,the structural characteristics of landslides have not been fully understood. In this study,the high-density resistivity method and audio-frequency magnetotelluric method were used to detect the landslide area,and the structural characteristics of landslides were revealed from the development of shallow karst and cracks,and the bottom interface of karst landslide.The stratigraphic structure of landslide area was divided by audio-frequency magnetotelluric method,and the lithologic interface between Qixia-Maokou Formation and Liangshan Formation was defined according to the electrical characteristics of different lithologic strata.Furthermore,the clastic rocks of Liangshan Formation in some areas were divided into shale,carbonaceous shale and coal seam. It is found that there are two layers of karst development:one is the karst fracture zone in the shallow part of the karst mountain,which is filled with mud and other low-resistivity substances,and the development depth of the karst layer gradually increases from northeast to southwest;the other is the deep karst fracture zone at the bottom interface of limestone in Qixia-Maokou Formation,which is mainly developed in the southern part of the landslide mountain,showing low-resistance characteristics.These two layers of karst structures provide a weak layer for landslide regeneration.Cracks and karst development areas have been detected by high-density resistivity method.There are three mountain cracks in the landslide mountain,including one with a large front edge and two secondary cracks at the rear edge.The cracks show the characteristics of"local high-resistance zone in the low-resistance layer on the surface and vertical low-resistance zone in the underground high-resistance rock mass".In addition,some shallow vertical karst fracture zones were detected,which destroyed the integrity of karst mountain.With the development of karst,karst mountain deteriorated into scattered fragments,which may gradually collapse or landslide under some extreme conditions.It is considered that the development of karst,especially the deep karst at the interface between limestone and shale,is one of the key factors leading to landslides.Together with the goaf formed by coal seam mining,karst development is the background condition that may trigger landslides,which in turn can deteriorate karst mountains into scattered blocks and gradually into collapses and landslides.The combination of audio-frequency magnetotelluric method and high-density electrical method can effectively detect the structural characteristics of karst landslides,and can comprehensively obtain the characteristics of karst spatial development,crack location and distribution of landslide bottom interface,which can provide an important basis for in-depth and comprehensive analysis of landslide stability.