MORPHOLOGICAL STRUCTURE AND FAILURE MECHANISM OF SHIDAGUAN TOPPLING BODY IN MAOXIAN BASED ON MULTI-SOURCE DATE

Data of surface morphology and underground structure(morphological structure) in the course of slope disaster are necessary in slope stability evaluation and disaster prevention. The "space-ground-interior" multi-source date joint analysis is an effective method for morphological structure research based on aerial telemetry,ground survey,internal real exploration and inversion. Morphological and structural investigation of the Shidaguan oversize toppling body(1388×10⁴m³),located on the anti-inclined slope of metamorphic rocks on the right bank of Minjiang River,was carried out by unmanned aerial vehicle(UAV)aerial survey,artificial ground survey,surface displacement monitoring(GNSS),drilling,exploration well and electrical resistivity tomography(ERT). The results show that the upper reaches(north side) of the Shidaguan toppling body are characterized by the collapse of debris and soil at the leading edge,multi-stage tension cracking at the middle and rear ends,and lateral margin en echelon shear,but the swelling and lateral cracking of completely weathered phyllite at the lower reaches(south side),with the maximum displacement of the upper reaches up to 24 times that of the lower reaches. The toppling fracture zone is step-shaped in the toppling direction,with a thickness of 0.8~10.3m and a buried depth of 35~75m,increasing from upstream to downstream. Further investigation of macroscopic and microscopic material structure shows that the shear slip in the upstream fracture zone is mainly marked by the secondary shear zone and the scratches,and the insitu weathering of the rock and reverse bend in the downstream fracture zone is the main characteristic. It is further found that the upper reaches of the Shidaguan toppling body belong to the traditional mode of "rock toppling→rear pull crack→base break→integral slip". The toppling of the downstream is inhibited by the blocking of mountain in the leading edge,the compressive stress of the front part is concentrated,and the basal body breaks and slippage occur after the shear failure of the extrusion part. Hence a new model of "rock toppling→rear pull crack and pressure stress concentration at the front→base fracture→front bulge,lateral crack,and back warping shear→integral slip" is proposed. The methods and results of the morphological structure survey are helpful to the analysis of catastrophic processes of similar slopes.