On Mechanism Of Pile-Soil Interaction And Technique Of Anti-Sliding

The geologic environment is friable in middle and west area of China. Some large-scale base establishment projects have influenced the geologic environment largely. The slope gravity hazards such as landslides, debris flow and collapse are retaining increased current. The destruction process of slope acted by gravitation is the self-organization process that rock and soil mass exert stabilization ability themselves to withstand the gravity action. In the process, the distortion behave as development from out-of-order to ordered. The anti-slide and reinforcement measure can change the the self-organization process and prevent the distortion of rock and soile mass developing from out-of-order to ordered. Based on self-organization theory, the strong outside disturbance can induce that the self-organization characteristic of system may disappear and behave as large-scale destruction abruptly, such as earthquake status, the slope may been destroyed abruptly. Aiming at upwards two typical destruct process of slope, different design idea should been adopted. For normal status, the main idea is to utilize the ability of rock and soil mass own stabilization adequately. For earthquake status, the main idea is to strengthen the aseismatic capability of the whole slope and reduce the coupling amplificatory effect of the outside disturbance, such as altering the dynamic characteristic of slope.As one kind of familiar and effective measures to deal with the slope gravity hazards, anti-slide piles are absence of theoretics guidance. Especially, in respect of confirming the reasonable pile space, engineering experience is main depended on. The mechanism of some familiar anti-slide and reinforce measures is studied rarely in seism condition. Based on geotechnical centrifuge model tests and shaking table model tests, combined with numerical simulation calculation, the pile-soil interaction mechanism and anti-slide reinforce technique in seism were studied. The main work and conclusion is as follow:(1) Geotechnical centrifuge model tests combined with numerical simulation calculation were adopted to reappear the soil-arching phenomena between piles. The critical net pile space is 5-6.25 multiple the pile width under experiment condition. The results of tests and calculation indicate that the form of soil-arching is same nearly, vector height increases with the pile space basically. Height-span ratio is 0.4～0.6 approximately. Force of pile and distributing of principal stress indicate that the foot of soil-arching is the dominate section. Thrust of foot is transferred to pile via soil at the back of pile mainly. The counter-force provided by the friction of pile flank and soil is 10% of the former. By sensitivity analysis, the sequence of factors that influence the critical pile space is: residual slip force of sliding mass, internal friction angle of soil mass, cohesion of soil mass, width of pile. Based on the research conclusion, the calculational model of critical net pile space is founded by multiple regression analysis, which can be used to estimate condition of forming the soil arching between piles and optimize the design of pile space.(2)Based on the pseudo-static method theory, the failure mechanism of slope accumulation reinforcement under earthquake was studied with centrifuge model tests and numerical simulation. In order to reinforce slope accumulation, anti-slide piles and anti-slide piles combined with anchor bolt frames were analyzed by means of contrast. Experimental results show that overtopping collapse possibly occur when anti-slide piles are used solely to reinforce the foot of slope accumulation. Anti-slide piles combined with anchor bolt frames can meliorate the distributing of stress and strain, and minish the deformation of slope and the force of anti-slide piles greatly. The determinant condition about failure mode of overtopping collapse is put forward, which can be used as guidance of prevention project design. It is suggested that the principle of "foot reinforcement and mountainside strengthening" should be emphasized for slope accumulation engineering design in high earthquake intensity regions. To carry out technique and economy optimum design, amount of piles project can be reduced when the anchor bolt frames are adopted.(3)Through Contrastive tests of no anchor bolt slope with anchor bolt reinforced slope by rockshaking table model tests, the phenomena is discovered that the acceleration amplificatory ratio of anchor bolt reinforced slope is less than no anchor bolt slope distinctly, which shows that anchor bolt reinforced slope has preferable effect, especially at the state of middle and high earthquake. The result of spectrum analysis shows that the natural frequency of anchor bolt reinforced slope is improved 20% than no anchor bolt slope before the earthquake forece is loaded, which does not reduce obviously after middle and high earthquake when the natural frequency of no anchor bolt slope redues 20%. This illuminates that anchor bolt can ameliorate the earthquake qualitative behavior of slope. Comparing pseudo-static with dynamical analysis about the same model, the shear stress of soil and force of pile of pseudo-static calculation are less than those of dynamical calculation when the earthquake comprehensive affecting coefficient is adopted from design criterion. Pseudo-static calculation is not safe at the situation of middle and high earthquake. Farther calculation indicates that the reasonable range of earthquake comprehensive affecting coefficient is in 0.45～0. 5.