不同土质条件下高能级强夯加固效果测试与对比分析

为了探讨山谷型与滨海型两种不同土质条件下碎石回填地基的强夯加固效果,开展了8000kN·m能级的现场强夯对比试验;同时考虑滨海大型工程建设地基处理施工的需要,在沿海地区实施了10000,15000kN·m高能级强夯的现场试验。通过对各场地不同能级试夯前后地基动力触探与静力载荷试验结果的分析与对比研究,得出如下结论:①采用8000kN·m夯击能处理山谷型厚层碎石回填地基,其有效加固深度可达10.0～11.5m;处理滨海型下卧软弱夹层且存在地下水的碎石回填地基,其有效加固深度为8.5～9.0m;②采用10000kN·m夯击能处理滨海山前厚层碎石回填地基,其有效加固深度为12～12.5m;③采用15000kN·m夯击能处理滨海型下卧软弱夹层且存在地下水的碎石回填地基,其有效加固深度为11.5m;④若采用梅纳公式的修正形式预估强夯的有效加固深度,其修正系数取值范围建议为0.29～0.40;对于软弱下卧层浅、高地下水等不利情况应取低值,对于回填碎石层厚、且级配较好时可取高值。

Improvement effect of high energy dynamic compaction under complicated geological conditions

A series of experiments of high energy dynamic compaction(HEDC) with 8000,10000,15000 kN·m are conducted on rubble fill sites underlain by thin soft clay layers in coastal areas and in mountain valleys,respectively.The results of cone dynamic penetration test(DPT) and plate loading test(PLT) for several sites are systematically analyzed and compared with those before HEDC.Some conclusions concerning the effective depth of improvement(EDI) on the rubble fill sites in mountain valleys or those underlain by thin soft layers in coastal areas under various HEDC are drawn.It is recommended that the EDI should be pre-estimated by the revised Menard Formulation,with the revised coefficient within 0.29～0.40.Especially,the low value should be used under the condition of the thin soft strata and shallow groundwater levels.