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基于圆孔扩孔理论,考虑挤密砂桩挤密过程中砂桩本身的挤密体积变化,建立了砂桩桩身压缩模量的计算方法。采用Mohr-Coulomb屈服准则计算桩周土屈服区范围,同时结合桩间土的e-p曲线压缩理论,提出了基于扩孔理论的桩周土平均压缩模量计算公式,从而提出了考虑埋深影响的分层桩土应力比计算方法。结合越南河内-海防高速公路实际工程进行了计算分析,随着套管直径增大(0.5~0.6 m),挤密砂桩和桩周土的压缩模量都变小,但平均桩土应力比增大,从2.56增大至2.72,这符合《复合地基技术规范》中对于无实测资料时,桩间土强度低时桩土应力比取大值,桩间土强度高时取小值的规定。桩土应力比理论计算结果处于规范建议取值2~3之间。说明理论方法合理可靠,从而提高了挤密砂桩设计的科学性。
Based on the theory of hole enlargement and hole enlargement, the calculation method of compressive modulus of sand pile is established considering the change of the compacted volume of sand pile itself during the process of compacted sand pile compaction. Based on Mohr-Coulomb yield criterion, the range of yield zone of soil around piles was calculated. Based on the theory of ep curve compression of soil between piles, the calculation formula of average compressive modulus of soil around piles based on hole expansion theory was put forward. Stratified pile - soil stress ratio calculation method. Computation and analysis of the actual project of Hanoi-Haiphong Expressway in Vietnam showed that with the increase of casing diameter (0.5 ~ 0.6 m), the compressive modulus of compacted sand pile and surrounding soil became smaller, but the average pile-soil stress ratio Increased from 2.56 to 2.72, which is in line with the “composite foundation technical specifications” for the absence of measured data, the pile soil strength between the piles when the soil stress ratio to take large value, soil strength between the piles to take a small value . The theoretical calculation result of pile-soil stress ratio is in the range of 2 ~ 3. This shows that the theoretical method is reasonable and reliable, which improves the scientific design of the compacted sand pile.