土钉墙-桩锚-内撑复合支护体系监测与分析

对郑州市某深基坑工程的施工全过程进行现场监测，通过分析坡顶水平位移、冠梁水平位移和支护桩深层水平位移等监测数据，研究土钉墙-桩锚-内撑复合支护体系的变形规律；结合工程实例建立了有限元模型，将实测数据和数值分析结果进行对比，验证模型及参数适用性，进而总结了内支撑位置、锚索锁定值对支护结构变形的影响。结果表明:土钉墙-桩锚-内撑复合支护体系中坡顶水平位移主要由上部土钉墙控制；该体系支护桩深层水平位移曲线大体呈P形，最大位移出现在内支撑附近，产生于钢筋混凝土内支撑形成强度之前；随内支撑标高上移，桩身最大位移点向基坑底面方向移动，在复合支护体系中内支撑标高的确定应以基坑外被保护对象的位置为依据；桩身最大水平位移所在位置随锚索锁定值的增大而下移，且最大水平位移值减小；当场地的工程地质条件较好时，可以通过适度增大锚索锁定值来控制支护结构水平位移。

Monitoring and Analysis on Composite Support System with Soil-Nailing Wall-pile Anchor-inner Bracing

The field measurement of the whole construction process of a deep foundation pit engineering in Zhengzhou city was carried out. Through analysis of monitoring data such as the horizontal displacement of slope top and top beam, deep horizontal displacement of support pile, the horizontal displacement law of composite support system with soil nailing wall pile anchor-inner bracing was studied. Combined with the engineering example, the finite element model was established, the measured data and numerical analysis results were compared to verify the applicability of model parameters, and then the influences of inner bracing position, anchor lock value on the deformation of support structure were summarized. The results show that the horizontal displacement of slope top is mainly controlled by the upper soil nailing wall in the composite support system with soil nailing wall-pile anchor-inner bracing. The deep horizontal displacement curve of the support pile in this system is generally “P” shape, and the maximum displacement occurs near the inner bracing, which is produced before forming strength of reinforced concrete inner bracing. As the elevation of inner bracing moves upward, the maximum displacement of pile moves towards the bottom of foundation pit. In the composite support system, the determination of the elevation of inner bracing should be based on the location of protected objects outside the foundation pit. With the increase of anchor lock value, the maximum horizontal displacement position of pile body moves down and the maximum horizontal displacement decreases. When the engineering geological condition of the site is better, the horizontal displacement of support structure can be controlled by increasing the anchor lock value appropriately.