模量对搅拌桩复合地基承载性能影响的数值研究

Numerical study of the effect of material modulus upon cement-soil pile composite foundation

在现场试验的基础上,利用FLAC3D建立数值模拟模型,分别改变复合地基的褥垫层、持力层和桩体材料的模量,计算采用不同模量时复合地基的沉降以及桩土的应力,分析模量变化对复合地基承载力和沉降的影响规律。结果表明,褥垫层的材料和模量影响到桩间土承载力的发挥,褥垫层宜采用级配砂石,模量取值范围为20～50MPa。持力层模量增大可以提高复合地基承载力减小沉降,因此水泥土搅拌桩的桩端要进入到具有一定硬度的土层中,除软弱土外,其他土层做持力层其强度对复合地基承载力和沉降的影响不大。在一定范围内增大桩模量可以有效提高复合地基承载力减小沉降,采用水泥土搅拌桩加固软土地基时,桩的模量不要过大,建议取值范围为200～400MPa。

Numerical simulation model was established with FLAC3D to calculate the stress of pile and soil and the settlement of composite foundation with different modulus of cushion,bearing stratum and pile.The rules of the effect of material modulus upon cement-soil pile composite foundation have been obtained.The results show that the bearing capacity of soil between piles is affected by the material and modulus of cushion,so graded joint sand is appropriate for cushion,and the range of cushion modulus is from 20MPa to 50 MPa.The bearing capacity of composite foundation can be increased and the settlement of the composite foundation can be reduced if the modulus of bearing stratum is increased,so the bottom of pile should be located in the stratum with higher modulus.The strength of bearing stratum has no notable effect on the bearing capacity and the settlement of composite foundation except soft soil.The bearing capacity of composite foundation can be increased and the settlement of the composite foundation can be reduced effectively if the modulus of pile is increased with a certain range.Quite high modulus of pile is not used in cement-soil pile composite foundation,and the reasonable range of it is from 200MPa to 400 MPa.