Experimental Study On The Mechanical Behavior Of Double-Row Anti-Slide Piles Installed In Parallel

As a new type support system with combined,static and fixed structure,the double-row anti-slide pile has been widely used in large-scale landslide disaster control projects due to its advantages of large rigidity,small disturbance and good supporting effect.The double-row anti-slide pile support system is complex,and the proportion of the landslide thrust in the front and rear is not clear.In the actual double-row anti-slide pile design,the ratio of the front and rear piles is usually 1:1 or 1:2,which will cause material waste or safety hazards.And the current failure mode of double-row anti-slide piles is not clear.Therefore,the sharing ratio and failure mode of double-row anti-slide piles need to be further studied.On the basis of summarizing the theories of predecessors,this paper carries out a full-buried parallel-type double-row anti-slide pile model test of the joint beam,and studies the force characteristics under the ultimate load when the pile spacing is 5 times the pile diameter.According to the analysis of the test data,the landslide thrust sharing ratio and the bending moment distribution rule of the double-row anti-slide piles and the failure modes of the piles are obtained.Comparing it with the conclusions of the parallel arrangement of the double-row anti-slide piles without joint beams,people can select the optimal supporting type.Finally,the ABQUS numerical simulation software is used to calculate the model test to verify the rationality of the model test.The main results are listed in the following parts:(1)Under the action of ultimate load,the double-row pile retaining effect and the anti-confining strength of the parallel beam are better than the parallel arrangement of the double-row anti-slide pile without connecting beam.(2)The bending moment distribution of the double-row pile body is “S” shape,and the bending moment of the sliding surface position is almost zero.The bending moment ratios of the two groups before the experiment is 1:1.5 and 1:1.2 after the test.Except for the pile top,the thrust ratio of the rear pile and the front pile landslide is greater than 1,and the average value is 1.36;the soil resistance ratio is less than 1,and the average value is 0.57.(3)Under the ultimate load,the deformation of the double-row pile with coupling beam can be divided into three stages,which are: elastic deformation stage,plastic deformation stage and failure stage.However,the double-row pile without joint beam only has elastoplastic deformation stage and failure stage.(4)The failure modes of the piles in the two groups are similar,all of which are bending failure,showing “S” shape deformation.The degree of failure of the rear piles> the degree of failure of the front piles,and the damage of the piles in the joint beam test is more serious,and the damage points are more.The damage position is farther away from the sliding surface.Specifically,the pile body produces two plastic hinges,and the sliding surface and the lower sides are subjected to bending damage.Specifically,when the pile body is close to the sliding body side,crushing damage occurs above the sliding surface,and tensile failure occurs below the sliding surface.On the contrary,when the pile body is away from the sliding body side,tensile damage occurs above the sliding surface,and crushing damage occurs below the sliding surface.(5)In order to manage the large-scale landslide disaster more economically,reasonably and effectively,it is recommended to adopt the full-buried double-row anti-slide pile type with coupling beam.The proportion of the piles in the front and rear rows is recommended as 1:1.3~1.4,and people should strengthen the bending strength from h1(1/5 pile length)above the sliding surface to h2(1/6 pile length)below the sliding surface.