Stability And Controlling Measures Of Fan Shen Hao Zi Landslide Under Excavation Condition

The landforms are mountains and hills in the central,western and southeast of China.At present,these regions are building infrastructure projects,including highways,railways and other linear engineer ing.Due to the special terrain and geological conditions of these areas,many linear projects need to be excavated.The stress state of the original slope will change dramatically due to the strong human engineering excavation.Thus,the local geological body can be separated from the parent body,and occur the obvious deformation and failure phenomenon.So,the original stable slope can transform into lands lide,or the original old landslide become resurrection.This will result in devastating damage to the existing line construction or existing structures,and may cause great casualties and loss of property.There are too many this types of landslides.So,study on the deformation and failure characteristics,stability and controlling measures of the slope under the engineering excavation,which has important engineering value to protect the safety of highway engineer ing.It is also an important scientif ic issue in the field of geological engineering and geotechnical engineering.This paper takes the Fan Shen Hao Zi landslide in the G7 highway Jining to Hohhot section as the object of study.By means of field investigation,laboratory test,field monitor ing,theoretical analysis and numerical simulation,the stability,controlling measures and its effect are discussed deeply.In the course of the study,the engineering geological model of the landslide is proposed based on the geological characteristics and the deformation and failure of the slope.The transfer coefficient method and discrete element simulation are used to reveal the stability of the landslide and the deformation-failure process.Finally,the application of engineering structure design principle is proposed to put forward the landslide control scheme.Through repeated selection,the economic and effective controlling measures are determined,and the stability of the landslide is tested by the discrete element simulation.Through the study of this paper,the main conclusions are as follows:(1)Fan Shen Hao Zi landslide is a medium and middle landslide.The mudstone in the landslide slip zone is the worst,and it is easy to soften in water,which can easily lead to sliding of the sliding body.After the excavation,the cracks in the front and back of the landslides expand rapidly.So,the excavation is the main factor that leading to the lands lide.Based on the classification principle of landslide,the material composition and structure,dynamic origin,deformation and movement characteristics,development stage are analyzed.It is defined as newborn-incubation period-progressive push type-artificial excavation-rocky bedding landslides.On this basis,the landslide engineer ing geological model is established through the cross-section form.(2)Using normal distribution to fit the strength parameters of mudstone in the slip zone of Fan Shen Hao Zi lands lide,the expected value of cohesion is 52.912 kPa,the variance is 38.594,and the expected value of internal friction angle is 18.85°,the variance is 8.3908.Then,through the linear fitting of the mudstone strength parameters of different drilling depth,it is found that the relation between the cohesion and internal friction angle and the depth is not obvious.Together the test method,engineering geological analogy method and inverse algorithm,it is determined that the cohesion is 18 kPa and the internal friction angle is 14° of the strength parameters of the sliding zone.Based on this,the transfer coefficient method is used to analyze the stability,and the stability coefficient is 1.03 under the natural condition,and the stability coefficient is about 0.64 in the rainstorm,and the stability coefficient is about 0.77 under the earthquake conditions.(3)Based on the 3DEC discrete element program,the deformation and failure process of Fan Shen Hao Zi landslide is obtained.It can be divided into 3 stages,namely,the front unloading rebound,the rear failure slide,the front and back unified slide.The essential reason for the formation of the landslide is the geological structure conditions,especially the mudstone as the easy-slip stratum.The main external trigger factor is the engineering excavation,and the secondary triggering factor is rainfall.The mechanism of landslide is that the secondary stress field of landslide is easy to form a new fracture,and the cracks are easily formed and connected at the existing fractures.(4)According to the situation of Fan Shen Hao Zi landslides,take the emergency measures of cutting top and pressing foot,and filling and tamping the cracks.Based on the pier displacement monitoring results of Fan Shen Hao Zi bridge,the emergency measures is proved to be effective,and the landslide is prevented to continue to slide in the short term.Two long-term control schemes are proposed,and the optimal scheme is determined by comprehensive comparison.The rationality and effectiveness of the control scheme are confirmed by field macro observation,and the expected control effect is achieved.(5)The rationality and effectiveness of the control scheme are confirmed by field macro observation,and the expected control effect is achieved.Based on the 3DEC discrete element program,the solid element is used to simulate the anti-slide pile and the Cable element simulating anchor cable.Based on the analysis of landslide displacement,plastic zone and anti-slide pile and anchor cable,it can be seen that the stability of the landslide is high and the safety of the structure is good.Based on the strength reduction method,it is found that when the reduction coefficient is 1.95,the anchor cable and anti-slide pile will be broken.So,1.95 is the critical reduction factor,and the stability coefficient of the reinforced landslide is 1.95.