CFG桩基坑内施工对基坑周围环境稳定性的影响

发布时间：2019-05-26 23:05

【摘要】：在地下工程中,由于天然地基承载力不足,带有地下室的主体结构采用CFG桩复合地基。因为CFG桩长螺旋钻施工设备限制,地下室底板下的CFG桩必须在深基坑开挖一部分后进行施工。在某深基坑工程中,随着CFG桩的施工,基坑周围地表出现明显开裂现象。为探究其原因,结合该基坑工程实例,利用FLAC3D软件,通过数值模拟分析考虑渗流作用下CFG桩基坑内施工对基坑周围地表变形的影响规律,并把计算结果同实际监测数据进行对比分析。研究结果表明:CFG桩在部分开挖基坑内施工的快速取土作用对基坑内被动土压力区产生扰动,削弱原有的被动土压力,导致基坑周围土体变形。基坑周围地表变形的影响范围超出2倍基坑深度的监测范围,因此,部分开挖基坑内施工CFG桩的基坑工程周围环境的监测范围应在满足国家规范要求的基础上适当增大。根据计算结果建议类似基坑工程监测范围距基坑边缘的距离采用基坑开挖深度与基坑底面以下CFG桩长之和。类似基坑工程设计应加大支护结构和止水帷幕深度,施工时从基坑内部向外部隔桩跳打,并适当增加工期,将有利于降低由于CFG桩基坑内施工对基坑周围土体的影响。
[Abstract]:In underground engineering, due to the lack of bearing capacity of natural foundation, CFG pile composite foundation is used in the main structure with basement. Because of the limitation of CFG pile length spiral drilling construction equipment, CFG pile under basement floor must be constructed after deep foundation pit excavation. In a deep foundation pit project, with the construction of CFG pile, the surface around the foundation pit appears obvious cracking phenomenon. In order to explore the reason, combined with the foundation pit engineering example, using FLAC3D software, the influence of CFG pile foundation pit construction on the surface deformation around the foundation pit under seepage action is considered by numerical simulation and analysis. The calculated results are compared with the actual monitoring data. The results show that the rapid soil extraction effect of CFG pile in part of the excavation foundation pit interferes with the passive earth pressure area in the foundation pit, weakens the original passive earth pressure, and leads to the deformation of the soil around the foundation pit. The influence range of surface deformation around foundation pit is more than 2 times the depth of foundation pit. Therefore, the monitoring range of surrounding environment of foundation pit construction with CFG pile in part of excavation foundation pit should be properly increased on the basis of meeting the requirements of national code. According to the calculation results, it is suggested that the distance between the monitoring range of similar foundation pit engineering and the edge of foundation pit should be the sum of the depth of foundation pit excavation and the length of CFG pile below the bottom of foundation pit. The design of similar foundation pit should increase the supporting structure and the depth of water stop curtain, jump from the inside of the foundation pit to the outside of the foundation pit, and increase the construction period appropriately, which will be beneficial to reduce the influence of the construction of CFG pile on the soil around the foundation pit.
【作者单位】：河北工业大学土木工程学院;河北省土木工程技术研究中心;河北省建筑科学研究院;
【基金】：河北省建设科学技术研究计划(2012-156)
【分类号】：TU753

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