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| Model tests on multi-interface shear performance of jet grouting soil-cement-pile strengthened piles in homogeneous sand |
| REN Lianwei1，LV Chenchen1，WANG Xinyu1，DUN Zhilin1，WANG Junlin2 |
| (1. School of Civil Engineering，Henan Polytechnic University，Jiaozuo，Henan 454000，China；2. School of Water Conservancy and Environment，Zhengzhou University，Zhengzhou，Henan 450001，China) |
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Abstract Comparative model tests on the bearing capacity and the multi-interface performance of jet grouting soil-cement-pile strengthened piles(JPP) with four different combinations(upper，lower，segment-Ι and segment-II) under compressive and uplift loads were carried out based on large-scale pile foundation load test equipment system. Model piles were buried by sand pour method. Model test results show that：(1) The bearing capacity of JPP piles is affected greatly by combination forms. Particularly，the segment-II combination can achieve the maximum bearing capacity in compressive load test while the lower combination can achieve the maximum value in uplift load test，indicating that JPPs should be segmented and the soil-cement segment should be placed in the lower of JPP piles in the engineering design. (2) The uplift bearing capacity is about 10%–15% of the compressive bearing capacity，and the average side resistance under uplifting load is approximately 13%–20% that under compressive load. (3) The side resistance of JPPs under both compressive and uplift loads increases with increasing the relative displacement between pile and soil in a hyperbolic form. The relative displacements necessary for the side resistance of JPPs reaching the limit value are around 2 and 7 mm under compressive and uplift loads，respectively. (4) At the initial stage of loading，the interface friction increases rapidly with a small relative displacement between core pile and soil-cement，and the interface shear stiffness tends to infinity. With increasing the load，the interface shear stiffness decreases while the relative displacement increases，showing a flexible work stage. As the load increases further，the interface friction increases faster and soon reaches the shear failure. (5) The interface shear stiffness between core pile and soil-cement under compressive and uplift loads is about 400 and 200 times that between cement-soil and soil around JPP，respectively，which ensures that core pile and cement-soil can work together to enlarge the diameter and to increase the bearing capacity.
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2022, Vol. 41 
