悬臂预应力SMW工法新型挡墙结构是在水泥土挡墙中插入型钢,于挡墙后侧布设垂直预应力锚索,型钢与锚索之间设置刚性的钢筋混凝土盖板梁组成的一种新型的基坑支护。为明确该新型结构的受力特性,对其受力过程进行了分析,探索合理的变形计算模型,并采取控制变形措施。具体方法是将型钢—水泥土复合体视为一个整体构件,建立变形微分方程和边界条件,采用两种算法开展变形计算:算法一是在先张预应力作用下计算其变形;算法二是在型钢顶部受附加弯矩计算其变形。以某深基坑施工全过程为例,对挡墙进行了实测统计分析,结果发现:理论计算变形值与监测值基本一致,而按现行规范忽略水泥土力学贡献及预应力的作用计算方法,所得到的变形值远大于监测值;在相同地质和基坑深度条件下,该新型挡墙结构通过后侧布设垂直预应力锚索可有效增加挡墙刚度,展现良好的抵抗变形能力和工程性价比;算法一、二的受力分析方法、计算模型、计算式能较好模拟这新型挡墙结构实际受力变形特征,为该新型挡墙应用于实际工程提供了理论支持。
The new retaining wall structure of cantilever prestressed SMW construction method is a new type of foundation pit support composed of inserting profile steel in the front of the cement soil retaining wall, setting vertical prestressed anchor cable in the back, and setting rigid reinforced concrete cover beam between the two. To clarify the mechanical behavior of this new type of structure, the stress process is analyzed, the reasonable deformation calculation model is explored, and the deformation control measures are taken. The concrete method is to regard the steel-cement soil composite as a whole component, establish the deformation differential equation and boundary conditions, and the deformation calculations are performed using two algorithms: In algorithm 1, its deformation under the action of pretension prestress is calculated; In algorithm 2, the deformation of the section steel top is calculated by the additional bending moment. Taking the whole construction process of a deep foundation pit as an example, the measured statistical analysis results of the retaining wall show that the theoretical deformation values are basically consistent with the monitoring values, while the deformation values calculated by ignoring the mechanical contribution of cement soil and the effect of prestress according to the current specification is far greater than the monitoring values. Under the same geological and foundation pit depth conditions, the vertical prestressed anchor cable at the back of the new retaining wall structure can effectively increase the stiffness of the retaining wall, exhibiting good deformation resistance and engineering cost performance; The stress analysis method, calculation model and calculation formula of algorithms 1 and 2 can better simulate the actual mechanical deformation of the new retaining wall structure, and provide theoretical support for the application of the new retaining wall in practical engineering.
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