Study On The Load Distribution Regularity Of Double-Row Drilled Anti-Slide Piles

Based on the method of numerical simulation and indoor model test, this passage analyzed the thickness of bearing platform, piles row distance, piles spacing, the landslide thrust, embedded depth, pile length and other factors of platform-type double-row drilled anti-slide piles in piles’ displacement and internal force of pile and soil resistance distribution and the load sharing law between double row piles. On the basis of comprehensive analysis, the optimization design was carried out, and put forward the double-row anti-slide piles’ sharing ratio in each factor changes, which provides the basis for improving the design and calculation of double row anti-slide piles. The main research results are as follows:(1) The maximum equivalent stress of the piles appears near the slip surface, the inner connection of piles and pile bearing platform is easy to appear the phenomenon of stress concentration, structural damage to these areas, attention should be paid to the encryption of reinforcement. With the bearing platform on the top of the piles’ internal force distribution of pile can coordinate and make the double row structure’s force more reasonable. The thickness of the platform is recommended for the diameter of the pile 1/2~3/4.(2) Earth pressure distribution for platform-type double row anti slide piles, rear row pile thrust a parabola distribution and resistance of rectangular distribution; former row pile thrust and resistance are distributed in a triangle. Earth pressure distribution for no platform-type double row anti slide piles, rear row pile thrust a parabola distribution, Force center offset and resistance of triangular distribution; The former row pile thrust force is rectangular and resistance are distributed in a trapezoidal. Due to slide surface’s friction, pressure of soil showed a decreasing trend in the near surface.(3) The reasonable value range of platform-type double-row anti-slide piles’ row distance and piles spacing is 3D~5D. Reasonable pile embedded depth of the pile length is 1/3. The longer the pile, the thickness of sliding body is bigger, the ratio of load to bear more of the rear row pile. When the former row pile’s section stiffness ratio K=0.8 to rear row pile, the maximum bending moment of pile body is 0.8 times, the pile diameter is 0.946 times of rear row pile, At this point the piles can play the effect of anti slide pile material best.(4) Analysis of influence factors on the design of double row anti slide piles load sharing, that when design measure by the shear load, rear row pile and former row pile’s sharing ratio is 6.0:4.0; when design measure by the moment, rear row pile and former row pile’s sharing ratio is 5.5:4.5.(5) The indoor model test results show that the pile row spacing is more big, the overall stability of pile-soil structure system is better, stronger ability to resist deformation. 3D pile row distance’s load ratio of rear row pile and the maximum bending moment of the former row pile is 1.43 on average, 5D pile row distance is 1.38, Their pile load sharing ratio is about 5.8:4.2. Model test results and existing engineering example to monitor the rear pile correspond to the former pile ratio 1.35,load sharing ratio is 5.7:4.3 similar, indicating that the test results is rationality, Evidence of the foregoing numerical simulation suggested sliding piles design load sharing ratio using 5.5: 4.5 is feasible, and proved that the former and rear row piles according to the load average allocation principle of design is not reasonable.(6) In the model test, when the load sharing ratio of the rear row piles to former row piles is measured by soil pressure(external force) is about 6.8:3.2, when by bending moment(internal force) is 5.8:4.2, Mainly because the former row piles not only bear landslide thrust, but also bear part of the rear piles’ landslide thrust which passed to the former piles by the platform, the presence of the pile platform makes the rear and former row piles internal force distribution coordination. The rear row piles mainly play a major role in the thrust of the landslide, and the former row piles play a role in enhancing the rear row piles.(7) The indoor model test shows that piles’ earth pressure distribution variation are basically consistent, landslide thrust behind the pile is a parabolic distribution and resistance in former of pile is rectangular distribution. With the depth increasing, the rear pile thrust on the sliding surface more than 1/2 reach maximum sliding body thickness and then gradually decrease, the former pile thrust on the sliding surface more than 1/3 of sliding body thickness after reaching a maximum and then gradually reduce. Due to slide surface’s friction, near the sliding surface of landslide thrust all showed a trend of decrease.