| Anti slide pile is the most commonly used means of slope instability, micro steel pipe anti slide pile as anti slide pile is a new type of form, with small construction machinery, pile layout are flexible, fast construction speed, small vibration, the adaptability to the construction site of the strong, on the environmental impact and many other advantages, which attracts more and more engineers of all ages. Earthquakes often cause micro steel pipe anti slide pile structure instability, causing huge economic losses, the micro steel pipe anti sliding pile aseismic performance so as to provide guidance for the design and construction of the structure has important practical significance. In this paper, considering the joint action of anti slide piles(Group) and soil mass, the structure is considered as the composite structure of piles.First on the composite structure considering soil arching effect of theoretical analysis, calculation of micro steel pipe pile reasonable pile spacing and the structure internal force combination calculation; then according to the similarity theory, the selection of similar material, the similitude design of model, the model of low cyclic loading, pile of pile and soil in composite structure, soil response for both materials, the strength of the pile- soil composite structure, failure morphology and dynamic properties. The main results of the research are as follows:(1) calculation of reasonable pile spacing considering the effect of soil arch. Hypothesis of landslide thrust uniform role on soil arch between piles, reasonable arch axis is a parabola, arch on any section of the pressure only and no bending moment and tensile force, selected soil arch calculation model, given a reasonable arch axis equation, arch height, the formulae for calculating the derived reasonable pile spacing.(2) the internal force calculation of the composite structure. Using the cantilever pile method, the frame structure of three micro piles is taken as an example, and the internal force of combined piles is calculated by plane problem.. For the calculation of the basic ideas, for safety, according to the most unfavorable situation, take no account of the role of soil between piles, broken out by the displacement method of structural mechanics, only calculating the bending moment of the piles and pile caps the landslide thrust, by the bending moment of pile caps for axial force of pile.(3) the low cycle reciprocating test equipment for the structural model test of the straight shear type anti slide pile is developed independently.. From Thompson’s research ideas developed a direct shear type anti slide structure model test equipment. The equipment is mainly composed of a shear system and the loading system of two parts, including four main parts, the upper shear box, a lower shearing box, anti power wall and a loading device.(4) the distribution of the soil pressure after the pile is tested. Bring forward more active earth pressure is roughly triangular distribution, landslide sliding pile body tilt, the whole pile model presented in sliding zone at the point of small angle rotation along the pile to soil pressure box with the pile body cooperative motion more, leading to soil and pile squeezing smaller; sliding belt, pile embedded in rock, not enough with the soil sliding soil pressure box attached to the pile body is kept fixed, so affected by pile soil depth of extrusion, resulting in soil pressure box measurement to the earth pressure surge pile head cap plate soil pressure is zero, the sliding zone soil pressure value is larger, the pile head to slide, earth pressure is more and more big, and the larger the speed more and more quickly.(5) the distribution of the soil resistance force before the pile is tested. In front of the pile soil pressure for passive earth pressure, the soil pressure distribution about trapezoidal shape. Pile body tilted forward, in front of the pile soil by squeezing pile, pile head part by squeezing more, sliding zone squeezed less generally show a a pile head of the earth pressure is zero inverted triangular distribution; and weight of soil pressure is almost a triangular distribution regular and superimposed on such up is trapezoidal distribution.(6) the bending moment of the pile is circular arc.. The moment of the whole pile changes with the load, and the moment of the whole pile changes with the load.. Anti corners sometimes float up and down, sometimes fixed at the same point, always finding a moment to keep the moment almost constant..(7) the axial force from the head of the pile head is increasing with the axial force. As the displacement of the actuator is increasing, the trend of this increase is becoming more and more obvious.. With sliding and pile by soil sloping trend more and more obvious, the lateral earth pressure along the pile is a component, the component near the sliding zone at the pile head high, leading to pile head of axial force ratio in the slide zone axis force is small.(8) the displacement of the pile cap is larger. From the point of view of macro soil pile composite structure as a whole, the cap plate hanging to pick at the pile head and the movement of the sliding mass when subjected to sliding body is larger, the composite structure as a cantilever beam as pile head displacement is larger.(9) the existence of the cap plate plays an important role in the bending moment redistribution of the piles.. The cap plate is locked together with the head plate, and becomes a rigid body. The locked pile is no longer a cantilever structure, the bending moment distribution is more uniform, and the pile body is safer..(10) the form of failure of the composite structure. Cap plate near the soil has a lot of obvious cracks, bulge phenomenon, crushing failure phenomenon is obvious; sliding zone soil subjected to shear failure, a part of sliding zone soils exposed, sliding zone slide show broken pieces; airport surface shape of the concave cavity formed between the pile and soil, the phenomenon of direct proof of the soil arching effect.(11) composite structure of hysteresis loop is full, stiffness degradation degree is small, bearing capacity is slightly higher, pile soil structure plastic deformation with excellent performance, good energy dissipation characteristics. |
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