堆载加芯搅拌桩复合地基荷载传递与变形特性

Load Transfer and Deformation Characteristics of Pile Cored Mixing Pile Composite Foundation

加芯水泥土搅拌桩常被用于软土路基加固,为研究堆载作用下加芯水泥土搅拌桩复合地基的荷载传递规律、变形特性以及芯长比对其影响,结合实际工程案例进行现场基底沉降、地基深层水平位移、分层沉降、内芯桩竖向应力监测,构建不同芯长比三维有限元复合地基数值模型进行验证、对比分析。研究结果表明:在堆载作用下,软土路基加固区存在中性点,在中性点上下,钢筋砼内芯桩与水泥土外壳桩荷载传递方式有所不同,钢筋砼内芯桩主要承担上部竖向应力,而水泥土外壳桩由传递剪切应力转换为承担上部竖向应力;增加芯长比可以增加桩体的有效桩长,增长水泥土外壳桩承担传递剪应力功能的长度,减少作用在桩土界面的负摩阻力大小,有利于控制沉降;增加芯长比能有效减少基底桩顶以及桩间土的沉降量,减少桩间土的竖向应力分担。

The core cement soil mixing pile is often used for the reinforcement of soft soil subgrade.In order to study the load transfer law,deformation characteristics and the influence of the core length ratio of the composite foundation with core load,the settlement of the foundation,the horizontal displacement of the deep layer,the settlement of the layered layer and the vertical stress monitoring of the inner core pile were carried out in combination with the actual engineering cases.The three-dimensional finite element composite with different core length ratio was constructed.The results show that:under the loading,there are neutral points in the reinforcement area of soft soil subgrade.The load transfer mode of reinforced concrete inner core pile and cement soil shell pile is different from that of cement soil shell pile.The reinforced concrete inner core pile mainly bears the upper vertical stress,while the cement soil shell pile is transformed from the transfer shear stress to the upper vertical stress.The results show that the increase of core length ratio can increase the effective pile length of pile,increase the length of cement soil shell pile to bear the function of transmitting shear stress,reduce the negative friction resistance on the pile soil interface,and it is conducive to control settlement.Increase the core length ratio can effectively reduce the settlement of the pile top and the soil between piles,and reduce the vertical stress sharing between piles.