水泥搅拌桩施工引起深层土体水平位移分析

王志丰+王亚琼+谢永利

摘要：针对水泥搅拌桩施工时水泥浆的注入对周围地层造成扰动，从而引起土体发生水平位移的问题，介绍了以柱形圆孔扩张理论为基础的Chai方法及其计算步骤，应用Chai方法分析了试桩C1，C2的现场试验数据。结果表明：当C1完工时，实测水平位移随深度的改变而变化，水平位移最大值达到34 mm，桩底以下土体也会产生一定的水平位移；当C2完工时，实测水平位移随深度的变化趋势与单桩（C1）施工情况的变化趋势基本一致，水平位移最大值达到72 mm；Chai方法可以用于计算单根水泥搅拌桩施工的情况，而对于多桩施工情况，无法考虑施工顺序和桩身强度的影响，产生较大的计算误差；以土体水平位移不超过10 mm作为施工的安全控制值时，单根水泥搅拌桩施工对周围环境的影响范围大约为9 m。

关键词：地基处理；水泥搅拌桩；现场试验；水平位移；圆孔扩张理论；影响范围

中图分类号：TU472.5文献标志码：A

Abstract： During the installation process of soilcement columns， the surroundings of ground would be disturbed due to injection of grout， which could cause significant lateral displacements of subsoils. Chais method and its calculation procedure， which was developed based on the theory of cylindrical cavity expansion， were introduced. Chais method was adopted to analyze the field test results of installing two soilcement columns （C1 and C2）. The results shows： after the construction of C1， the measured lateral displacements change with the variation of construction depth， and the maximum value can reach to 34 mm， and there are some lateral displacements under the bottom of column； when the installation of C2 is completed， the variation of measured displacements with depth is identical with the trend after the installation of C1， and the maximum value can reach to 72 mm. Chais method can be used to predict the lateral displacements caused by installing a single column， however there will be some discrepancy for the case constructing several columns due to that the effects of construction sequence and the column strength cannot be considered in Chais method. If the lateral displacement to be less than 10 mm is taken as safety control value， the influence range caused by the installation of single soilcement column is about 9 m away from the column center.

Key words： ground improvement； soilcement column； field test； lateral displacement； theory of cavity expansion； influence range

0引言

随着中国基础设施的不断完善，水泥搅拌桩技术已经在中国土木工程领域得到了广泛的应用，如高速公路建设中软土路基的处理等[14]。水泥搅拌桩技术最早起源于日本，与其他混凝土桩不同[59]，其基本原理是将搅拌机械插入土层中，并注入水泥浆与土体搅拌混合，最终形成具有较高强度的水泥土桩[10]。水泥搅拌桩技术主要分为湿喷法和干喷法2种[11]，湿喷法施工时喷入的是液体状水泥浆，而干喷法施工时喷入的是水泥粉。经过多年的发展，各国学者在水泥搅拌桩复合地基承载性状、沉降性状等方面都取得了较多的研究成果。……