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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。
Aiming at the problems of dewatering and supporting of deep foundation pit engineering in soft soil area, a new type of supporting structure of self-drilling string-in-line anchor with drainage board and composite frame is proposed. Its structure and working mechanism are discussed in detail. Based on the expansion theory of column hole, the bearing capacity formula of drill string anchor under the influence of pore pressure was deduced. The numerical simulation software ADINA was used to calculate the bearing capacity of the drainage plate and its bearing capacity The influence law is analyzed, and finally the simulation value of bearing capacity is compared with the theoretical value. The results show that: (1) The drainage board has a good effect of precipitation, which can quickly and effectively dissipate the pore water pressure of the aquifer soil. (2) By comparing with the condition of non-draining board, it can be concluded that the draining board drainage measures can effectively reduce the axial force and the horizontal displacement of frame column. (3) The drainage board can dissipate the excess pore water pressure caused by the expansion of the carcass in time. With the dissipation of pore pressure, the displacement and strain of the soil in the axial direction of the anchor rod decrease, and the pullout bearing capacity of the anchor rod is improved. (4) The calculated value of the theoretical formula of anti-pulling capacity is in good agreement with the simulation value, which verifies the correctness of the formula of bearing capacity.