SMW工法桩在硬土地区复杂环境基坑中的应用

Application of SMW piles in a foundation pit project in the complex surrounding environment and the hard soil area

SMW工法桩具有施工工艺简单、经济可靠、适用性强、对环境污染小等优势。自从国外引进以来,在我国沿海软土地区运用广泛,但是在内陆硬土地区运用尚少,且规范标准、技术规程并不完善,一些要求存在争议。本文通过对鲁西南周边环境复杂的某基坑项目中SMW工法桩运用和改良的介绍,总结了在设计、施工过程中可能遇到的一些问题,并提出了相应的解决方法:在周边环境复杂、可放坡空间受限、环保要求高的中型基坑支护项目中采用该工法桩,较为经济可靠;不同软件的计算结果有所偏差,在设计阶段应选择当地认可的软件,选择合适的模型和参数进行计算,并根据经验优化计算结果;搅拌桩施工中的水泥掺量和水灰比直接影响到灰土混合物的强度、均匀性和流塑性,进而影响到型钢施工难度和质量,以及水泥土帷幕墙的止水效果,但目前硬土地区尚未形成统一的规范标准,需要根据现场实际情况试验获得最佳配比。

The SMW construction method has the advantages of simple construction process,economic reliability,high applicability and less environmental pollution.Since it was introduced from abroad,it has been widely used in the coastal soft soil areas of our country,but it is rarely used in the inland hard soil areas,and the standards and specifications are not well developed with some requirements remained controversial.This paper introduces the application and improvement of SMW piles in a foundation pit project in the complex surrounding environment in southwest Shandong,summarizes some problems that may be encountered in the process of design and construction,and puts forward corresponding solutions.It is more economical and reliable to use the method in the medium⁃sized foundation pit project where the surrounding environment is complex,the space for sloping is limited,and environmental protection requirements is strict.Since different software may lead to different calculation results in some degree,locally recognized software should be selected for the design stage with the appropriate model and parameters for calculation,and the calculation results are then optimized according to experience.The cement content and the water cement ratio for SMW piles directly affect the strength,uniformity and flow plasticity of cement⁃soil mixture,hence the difficulty and quality of steel construction,as well as the water sealing effect of the cement⁃soil curtain wall.But there is no unified standard for the hard soil area;thus,testing is necessary to obtain the optimum mixing ratio according to the actual site conditions.