胶结砂土的静力触探模型试验及离散元模拟

    THE MODEL EXPERIMENT TEST AND DISCRETE ELEMENT SIMULATION OF CONE PENETRATION TSET IN CEMENTED SAND

    • 摘要: 在砂土中掺入水泥制备人工胶结砂土,通过自行研制的静力触探模型试验装置,研究了砂土颗粒间的胶结对静力触探结果的影响。试验结果表明:锥尖阻力qc随着水泥掺量的增加而增大,qc值的增加主要是由于胶结砂土的黏聚力增加引起的;根据qc值估算胶结砂土的强度参数时,如果不考虑结构性的影响,将会高估胶结砂土的内摩擦角;初始剪切模量与锥尖阻力的比值Gmax/qc随着水泥掺量的增加而增大,因此可以根据Gmax/qc的大小定性评价砂土的结构性强弱。通过离散元模拟分析了颗粒间的胶结强度对qc的影响机理。模拟结果表明:贯入会导致探杆附近颗粒间的胶结发生破坏,颗粒间的胶结强度越大,颗粒发生移动所需要的力越大,锥尖周围颗粒的接触力越大,因此qc值随着胶结强度的增加而增大。研究结果可以为胶结砂土中静力触探测试数据的分析和应用提供理论指导。

       

      Abstract: Artificial cemented sands were prepared by adding cement into the sand,and the effect of cementation between sand particles on cone penetration test results was investigated by self-developed model experiment equipment of cone penetration test. The test results show that the cone resistance qc increased with the increase of cement content. The increase in qc value was mainly caused by the increase of cohesion of cemented sand. When estimating the mechanical parameters of cemented sand according to the qc value,if the influence of structure is not considered,the internal friction angle of cemented sand will be overestimated. The ratio of initial shear modulus to cone resistance Gmax/qc increased with the increase of cement content,so the structural strength of sand can be qualitatively evaluated according to the value of Gmax/qc. The influence mechanism of bond strength among particles on qc was analyzed by discrete element simulation. The simulation results show that the penetration caused the breakage of bonds among particles near the probe rod. The greater the bond strength among particles was,the greater the force required for particles to arise movement,the greater the contact force of particles around the cone tip,therefore,the qc value increased with the increase of bond strength. The research results can provide theoretical guidance for the analysis and application of cone penetration test data in cemented sand.

       

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