Research On Seismic Strengthening Mechanism And Its Pattern Of Faults Slope In Strong Earthquake Zone

Affected by the "5.12" Wenchuan earthquake, has occurred a lot of slope geological disasters in mountainous area of southwest of China. So, the stability of the slope is particularly important to highway construction In the meizoseismal area. As one particular case of all different kinds of slope instability, slope instability during the earthquake in fault zone has its own characteristics. Refer to relevant academic researches, reinforce slope of the fault zone with anti-slide pile only a few tilt deformation under the action of earthquake, most of the pile has not destructed, and the reinforcement of the slope is stable. Based on the above facts, selecting slope of fault zone along the Guanggan highway as the research object in this paper, using the method of numerical simulation to study those commonly reinforcement mode used in the design of highway slope, consisting of the without platform, platform with different dynamic response rules of high slope and slope anti-slide pile reinforcement mechanism and strengthening mode, basing on the study, to analysis the dynamic stability of the anti-slide pile of slope of fault zone along Guanggan highway. Through the study summarized main results as follows:(1) Under the earthquake, the higher the slope the horizontal displacement of slope body as a linear growth, and the horizontal displacement value of head and surface of slope is bigger, while the horizontal displacement value of the toe of slope smaller. Maximum principal stress centralized in the head and surface of slope and, when the height of slope is enough, slope formed relatively obvious stress concentration areas, and the toe of slope produce more obvious stress concentration area. Contrast analysis, the height of fault slope is higher, its stability worse under dynamic action. Recording horizontal displacement value of the slope with different time points under seismic action, It is found that horizontal displacement value increasing, slope deformation accumulation under the sustain action of seismic wave.(2) Dynamic deformation analysis of slope of fault zone show, due to the rock mass on fault zone loose and crushing, during seismic wave propagation in geotechnical slope body, the transverse wave and longitudinal wave made slope body interactions occurring at different positions of the slope rock mass, creating the tensile or shear deformation and even lead to slope rock mass failure. At the same time, seismic wave will occur reflection and superposition when encountered the transmission interface during the process propagation, different seismic wave will also synergy that induced the tensile deformation and shear deformation of rock and soil mass.(3) The FLAC3D software simulation the slope dynamic response characteristics before and after anti-slide pile support. The pile can significantly reducing the displacement values on top slope, constrainting the slope deformation and destruction on surface of slope. The anti-slide pile can reducing the distribution of plastic zone of slope, redistribution the slope stress, improving the stability of the slope.(4) Under the earthquake, recording the force distribution between the piles and soil and internal pile. The deformation of the top of pile is bigger than central, and easy to tilt and destroy. Shear has been formed at the beginning of earthquake, the next seismic action will only cause small changes in the shear, pile bending moment value is not big at the beginning of earthquake, and fluctuations near zero, it is increased to the maximum quickly with continuous effect of seismic waves. Pile bending moment variation as increased first then decreased along top to bottom of the pile, the maximum value in the near the middle position of pile body. It should add steel bar near the maximum internal force during the anti-slide pile design.(5) Comparison and analysis the presence of anti-slide pile dynamic supporting effect when there sliding surface or not. The displacement of soil between piles is gradually reduce from airport to the internal of slope body when no sliding surface, plastic deformation area focused on the surface of slope, top of slope with small deformation, the internal force of pile smaller; displacement of soil between piles is bigger first, then decreases when have a sliding surface, the deformation of the soil layer is large, the presence of large amounts of plastic deformation zone in top of slope, the soil is easier to move along the sliding surface in the direction of airport surface, anti-slide pile internal force value is bigger and prone to damage. It is important to note that the sliding surface of slope can significantly affect the displacement of soil between pile and pile, the displacement near sliding surface is largest.(6) This paper has summarized the reinforcement mechanism of anti-slide pile of fault zone of meizoseismal area. Under the seismic action of earthquake, creating seismic oscillation effect on slope, the fault fracture zone of rock mass occurring relaxation and deforming toward sliding surface during repeated oscillation. When seismic waves spread from slope to the anti-slide pile e, part of the force directly effect on pile body, another part of the force transmission to soil arch between piles, arch transfer pressure to the anti-slide pile by pressure, and the pile will transmission pressure to anchorage section of bedrock, achieve a best resistance. Meanwhile, a maximum shear of pile body generally located in the more easily slide area where intersect pile body, the shear force of middle pile reverse to two endpoints; Pile bending moment in the anchoring the following about2m to3m is largest and symmetrical distribution. Shear force and bending moment are increases first and then to decrease and total increases to the maximum with the seismic effect.(7) Contrast analysis of the different pile arrangement position, anchorage length and pile spacing, pile anchorage as8m,10m and12m in length, pile spacing5-10m the slope dynamic changes during the30m high model slope (the slope divided3excavations, excavations high10m),when slope ratio is1:1, anti-slide pile has the following rules:①The cantilever pile can reduce overall slope deformation value, all buried pile body internal force is small, and the excavated volume is small, convenient to construction;②The anti-slide pile anchorage long as10m and12m reinforcement effect is good than anchorage long as8m;③The pile spacing9m and10m slope has produced a large deformation, slope damage has occurred, the two kinds of pile spacing on the slope reinforcement effect is not good.