排水板复合框架自钻胎串式锚杆支护结构的工作机制分析

Mechanism of composite grillage support with self-drilling anchors of tire tandems and vertical sheet drains

针对软土地区的深基坑工程降水与支护问题,提出排水板复合框架自钻胎串式锚杆新型支护结构,对其结构构成和工作机制进行详细探讨。基于柱孔扩张理论,推导出自钻胎串式锚杆在孔压影响下的承载力计算公式,采用数值软件ADINA对排水板的降水效果及其对自钻胎串式锚杆抗拔承载力的影响规律进行分析,最后将承载力模拟值与理论值进行对比。结果表明:(1)排水板具有良好的降水效果,能够快速有效地消散掉含水层土体的孔隙水压力。(2)通过与无排水板的工况进行对比,得出排水板降水措施能够有效减小锚杆轴力和框架柱的水平位移。(3)排水板能够及时消散胎体膨胀引起的超孔隙水压力,随着孔压消散,土体沿锚杆轴向产生的位移和应变降低,锚杆的抗拔承载力得到提高。(4)抗拔承载力理论公式计算值与模拟值基本吻合,验证了承载力计算公式的正确性。

In order to solve the problems of draining and supporting for deep foundation pit in soft soil area,a new type of supporting structure with vertical sheet drains and self-drilling tire tandem anchors was put forward,and the working mechanism was studied in detail. The bearing capacity of the self-drilling tire tandem anchor under pore ware pressure was derived based on the cylindrical cavity expansion theory. The effect of prefabricated vertical sheet drain were analyzed and its influence on the uplift capacity of self-drilling tire tandem anchor was discussed with the finite element software ADINA. The bearing capacity value from simulation was compared with the theoretical one. The results show that the vertical sheet drains have a good dewatering effect,which can dissipate the pore pressure in the soil quickly and effectively. The axial force of anchors and the horizontal displacement of frame columns are significantly reduced with the prefabricated vertical sheet drains. The excessive pore water pressure caused by tire expansion can be dissipated immediately with the prefabricated vertical sheet drains. Furthermore,with the dissipation of pore water pressure,the displacement and strain of the soil along the axial direction are reduced,and the uplift capacity of anchors are improved. The theoretical uplift capacity is basically accordance with that from simulation,which proves the correctness of bearing capacity formula.