CFG桩桩土应力比及褥垫层厚度研究

通过CFG桩单桩及三桩复合地基原位试验 ,对CFG桩桩土应力比及褥垫层厚度进行研究。三桩试验的褥垫层厚度为 2 0cm ,试验加载为设计荷载的 2倍 ,加载至设计荷载时 ,桩间土压力为 2 30kPa ,大于原状土承载力 16 0kPa ,桩土应力比为 14 3,远远小于设计值 ,说明 2 0cm厚的褥垫层使桩间土的承载力发挥过大。CFG桩的反向刺入使天然土的承载力得以发挥 ,合理厚度的褥垫层应使桩土应力比接近计算值。试验研究表明 :褥垫层 5cm厚时的变形明显小于 2 0cm厚时 ,加载至 1 5倍设计荷载时桩头均未破坏 ,桩体的反向刺入均大于 1 5cm ,说明 5cm厚的褥垫层已足以使桩间土发挥作用 ,且有利于控制沉降

RESEARCH ON THICKNESS OF CUSHION AND PILE-SOIL STRESS RATIO OF CFG PILE

The relative between stress ratio of pile-soil and the thickness of cushion is researched by experimental and theoretical analyses.7 experiments were conducted,including tests on 3 piles and single-pile composite-foundations.The distribution of stress and deformation in the composite-foundation were measured.The thickness of the cushion for test of 3 piles was 20cm and the test loading was 2 times of the designed one.When loading toe the designed load the pressure between the piles was 230kPa which is 160kPa higher than the bearing capacity of the original soil.The stress ratio of pile-soil was 14.3,much less than the assumed stress ratio.When the thickness of cushion was suitable,the stress ratio is near to the assumed ratio.According to these measurements,when the thickness of cushion was 5cm,the deformation was less than the one of 20cm.Which was favorable for controlling settlement.