高能级强夯加固粗颗粒碎石回填地基现场试验

Field Test Evaluation of High Energy Dynamic Compaction on Coarse-grained Gravel Fills

利用能级为15 000kN.m的高能级强夯加固粗颗粒碎石回填地基,测试夯击过程中夯坑及其周边土体的沉降变形,并对强夯后的地基加固效果进行检测与评价.可发现,第1、2和3遍夯击时的平均夯坑深度分别达到4.38,3.71和1.93m,夯击过程中地表土体都发生沉降变形,并未发生隆起;利用多道瞬态面波法评价该场地强夯加固深度至少达到16.5m,并且在整个加固深度范围内,未出现软弱层,夯后地基承载力远高于设计要求值.最后,提出了利用Menard公式评价高能级强夯处理粗颗粒碎石回填地基有效加固深度时n值的范围,为同类场地条件下高能级强夯工程的设计、施工与检测提供了参考.

A field test study was carried out by using high energy dynamic compaction （HEDC） with 15 000 kN · m energy on coarse-grained gravel fill materials. In tile course of tamping, the settlement of the crater per drop was monitored for all impact points at the first three passes, and the ground surface deformations around three impact points were also measured. It can be seen that the average crater depths reach 4.38 m, 3.71 rn and 1.93 m for the first, second and third passes, respectively. Also, no ground heave was observed during construction. After HEDC, the spectral analysis of surface wave （SASW） test was undertaken before and after HEDC in order to determine the depth of improvement. The SASW measurements indicated the depth of improvement following HEDC was not less than 16.5 m and there were no obvious weak layer. Based on three plate-load tests, the allowable bearing capacities of the site after HEDC also met the design requirements. Finally, the n values in Menard formula was determined to calculate the improvement depth for HEDC of coarse-grained gravels. This provides the references for the design, construction, and detection of HEDC at similar sites.