松散回填土场地柔性墩强夯置换法地基处理

Dynamic Compaction Replacement with Flexible Earth Column for Soil Treatment in Loose Backfill Ground

我国南方沿海地区大面积高填方多采用砂砾质残积黏性土作为回填材料,辅助强夯进行地基处理。天然残积黏性土本身具有孔隙比大、压缩性低、遇水软化和易崩解的特点,而经搬运后用作大面积回填时,其孔隙比更大,压缩性增大,虽经分层碾压,但土层颗粒仍为松散状态。由于南方地区多为晴热干旱和多雨的气候条件,土的饱和度变化较大,造成强夯法地基施工时,极易形成或塌孔或吸锤等施工问题的不断转换,严重影响地基加固效果。为此,在普通强夯法施工工艺加固地基的基础上,提出了在强夯夯坑内回填同类残积土,经二次复夯形成柔性置换夯墩的地基处理方法,并采用多遍点夯之间回填、休止、复夯逐步递进的特定施工工艺流程,解决了此类场地强夯施工困难、处理效果差的问题。工程实践表明,采用该方法进行地基处理,施工方便,消除了塌孔、吸锤等现象;处理后的地基场地均匀,承载力大幅提高,变形小,能有效满足工程设计要求。

Residual sandy clay soil is normally used for large area leveling backfill material with dynamic compaction in coastal region in south of China. Natural residual clay soil have characteristics of big pore ratio, low compressive, soften and disintegration encountering water. When used for large area backfilling after transportation, its pore ratio become bigger, and its compressibility increased. Despite of be rolled, soil grain is still very loose. Due to the alternative hot dry and raining weather condition, saturation degree of change bigger, and easily to cause alternative happening for soil collapse and hammer absorption during construction. The effect of soil treatment is seriously decreased. Whereas based on the construction processing of commonly used dynamic compaction methods to consolidate subgrade, the method of dynamic compaction treat subgrade with flexible earth column have been put forward, which make backfill in tramping excavation with same backfill materials and to be compacted in double times, meanwhile the special processing procedure have been adopted in cyclic backfill, rest, re-tramp step by step forward between multi-times tramping. Thereby the problems of construction difficulties and low efficient of treatment have been solved. The engineering practice indicated this method is easily to construct, and avoid soil collapse and hammer absorption during construction. The subgrade after treated is uniform, and bearing capacity increasing, deformation reducing, the parameter can satisfy the requirements of engineering design effectively.