Experimental Study On Failure Mode Of Shallow Accumulation Layer Reinforced By Micro Pile

Slope reinforced by micro pile is a kind of high efficient, economic and reasonable way, it has the advantages that construction speed is quick, small slope disturbance, but its small diameter, large slenderness ratio, prone to bending failure. Therefore, to explore the stress mechanism, arrangement form and failure mode of pile has important guiding significance for practical engineering. This paper briefly introduces the nature of the accumulation, landslide causes, arrangement form of pile and calculate theory of p-y curve method, Based on the physical model test, the stress mechanism and failure mode of the micro pile reinforced shallow layers with different soil along the top of the underlying bedrock under the landslide is studied.Arrangement form of three rows piles is rectangle and vertical, row spacing is 10 times the pile diameter and set longitudinal connecting beam for each pile, the anchoring depth is 2/5 times pile length, row spacing were taken to 8cm,12cm,16cm, the water content of slope respectively is 4.38%,7.09%,11.10%, the density of slope is 1.294 t/m3,1.458 t/m3 and 1.676 t/m3,18 pairs of trials are conducted in different water content, density and row spacing, setting transverse connecting beam in the last experiment. By analyzing the displacement of pile head, soil pressure in front of pile and bending moment of the pile, micro pile stress mechanism and failure mode is related to soil properties and row spacing.When the soil density is 1.458 t/m, moisture content is between 4.38% and 11.10%, increasing row spacing (about 13D) can reduce the displacement of each pile, when the water content between 4.38% and 11.10%, the greater water content, the greater displacement, whereas smaller. Therefore, when the water content is larger, the distance can be increased appropriately, when the water content is smaller, the distance can be reduced appropriately. Under the condition of the same moisture content, loose soil should be used with small spacing (about 8D), dense soil should be moderate(about 10D).With soil, row spacing or the time of action of landslide thrust is changed, the distribution of the soil pressure in front of the pile is also changed, and each pile for landslide thrust size has no fixed relationship, even when the soil, row spacing is certain, the different position of each row of piles from the top of the pile to bear the relationship of the size of the landslide thrust is also different.The maximum bending moment of pile near the surface under the action of landslide thrust, when the soil is loose, anti sliding section overall tilt almost didn’t bend, first row first failure and the lateral soil collapse the upper part of the pile will be exposed. When the soil is dense, the bending moment of the pile is positive below the surface and sliding surface, sliding moment is negative, the third row first failure and collapse of the lateral soil in whole or in part.Under the action of landslide thrust, the reinforced zone top surface will crack, it is recommended that the reinforced area of the top surface of the timely repair or directly to the top surface of continuous casting into a concrete board in order to prevent the cracks, and the retaining wall, anchor, soil nail and other reinforcement to prevent the collapse of the lateral soil, so also suggest that the mini pile and other reinforcement of the combined.