| Due to the influence of topography and landform,special lithological combinations,and slope structure,the red layer in the east of Sichuan is a landslide-prone high-risk area.Local landslide hazards endanger people's lives and property safety.The Xinglangpo landslide in Xuanhan County of Sichuan Province is a red rocky landslide that occurred on September 5,2004 due to a heavy rain.The scale of the landslide is about 1.48 million m3.The systematic study of such a recent red-bed landslide is helpful to study the formation mechanism of red-bed landslides,which is of practical significance for understanding the formation conditions and mechanism of landslides in the red beds,and can provide technical support for disaster prevention and mitigation in the region.It is of great practical significance to safeguard people's lives and property,as well as to maintain public order.At the same time,a study on the stability evaluation of landslides is conducted to determine whether the landslide has hidden dangers and causes damage to the lower residents.Through systematic on-site engineering geological surveying,combined with basic geo-environmental conditions in the study area,drilling and other exploration methods,this paper mainly studied the lithological composition,morphological characteristics,material composition,and slope structure of the slope in detail.Based on the zoning characteristics of landslide deformation and failure,this paper analyzed the factors causing landslide,combining the nature evolution of sliding zone soils and mechanical models to analyze the formation mechanism of landslides.The numerical simulation software 3DEC was used to simulate and reconstruct the deformation and failure process of the landslide.Finally,the stability of the landslide at the present stage was evaluated by the limit equilibrium method.The main research contents and results are as follows:(1)The formation of the Xinglangpo landslide occurred in the bedding slopes of the inter-bedded sandstone and mudstone layer,which has a slightly steep upper half and slow bottom half.Affected by the syncline of Tingzipu,it was a slope that is steep in the upper and slow in the bottom.The slope gradually slowed down,the interface is 18-25°.And the sliding surface was the weak structural surface of the mudstone interface,and the rock formation is 128-140°with ?19-23°.The layer thickness is mainly concentrated in 15-35 cm,about 304 m in length,about 610 m in width,140 m in height difference.The average thickness is about 140 m in,and 1.48 million m3 in mass.Two early landslides accumulating in the lower part of the slope,and several geological deformations had occurred in history.(2)According to the differences in the characteristics of landslides and deformation and failure characteristics,landslides can be divided into slip zones,uplift-crack zones and skidding zones.The deformations are divided into tensile cracks and bulging cracks.The width of deformation crack is mostly between 10 and 25 cm.The length is generally 20~50m.In the middle,a curved uplift fracture zone with a length of about 412 m is developed.It is a shear outlet and the elevation height is 3~8m.From the perspective of mechanical mechanism,landslides are mainly divided into active force transmission areas and passive compression areas.From this,the landslide is a slip-curve type.(3)The landslide deformation characteristics,slope structure and morphological characteristics were analyzed.Combined with factors of the slope formation mechanism,the evolution process of the sliding belt soil was analyzed using microscopic structures and physical mechanics tests.Combined with the mechanical model,the critical length of landslides was verified,and the pre-slip stability of Xinglanpo landslide was judged.After the comprehensive analysis of landslide formation and evolution processes,the process was mainly divided into slight bending-bulging,strong bending-uplifting and bedding shearing.(4)To verify the formation mechanism of Xinglangpo landslide,numerical simulation software 3DEC was used to simulate the landslide under natural and heavy rain conditions,and this paper analyzed the changes in landslide under the two conditions.The deformation and failure process of the landslide under rain condition was analyzed,comparing with the actual situation.The entire landslide destruction process was divided into four stages: initial stress accumulation,slight bending-bulging,strong bending-uplifting,and bedding shearing.(5)Through qualitative analysis,the stability status of the Xinglangpo landslide at this stage was evaluated,and the landslide is currently in a stable state.Using the quantitative analysis of the limit equilibrium method,the main slip surface and the potential slip surface of the Xinglangpo landslide are in a stable or stable state under natural conditions.Under the heavy rainfall and earthquake conditions,both the main slip surface and the potential slip surface are in an under-stable state.The internal friction angle has a greater influence on the stability of the landslide than the cohesion. |
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