河床覆盖层是一种厚度大、组成结构复杂的不良粗粒土地基,在覆盖层上修建工程需要对其进行加固处理。强夯法是一种快速有效的地基加固技术,目前采用强夯法加固河床覆盖层时,尚缺乏合理的强夯加固效果评价方法,也难以准确获取强夯后覆盖层的工程力学特性指标。依托某具体工程覆盖层强夯加固项目,基于旁压模量当量密度法思路,综合采用原位密度试验、现场旁压试验、室内模型旁压试验、室内单元体力学试验等手段,提出了一种砂砾石覆盖层强夯处理效果综合评价方法,并获取了强夯后覆盖层力学特性指标。试验结果表明,强夯后覆盖层试验Ⅰ区和试验Ⅱ区浅部原位干密度分别较强夯前提升7.8%和5.3%。强夯后,6 m深度以上范围覆盖层的原位密度和旁压模量均有所提高,6 m深度以下范围覆盖层的旁压模量与强夯前接近,强夯主要对覆盖层浅部有加固效果,对于覆盖层深部的加固效果不明显。研究成果可为类似强夯加固工程提供借鉴。

[Objective] Riverbed overburden, which is characterized by significant thickness and complex composition, constitutes a poor coarse-grained soil foundation. Works built upon such overburden require reinforcement treatment. Dynamic compaction is a rapid and effective ground improvement technique. However, when applying dynamic compaction to riverbed overburden, there is currently a lack of reasonable methods for evaluating its reinforcement effectiveness, and it is difficult to accurately obtain the engineering mechanical properties after compaction. [Method] Based on a dynamic compaction project for overburden reinforcement and drawing on the concept of the pressuremeter modulus equivalent density method, this study employed a combination of in-situ density tests, field pressuremeter tests, laboratory model pressuremeter tests, and laboratory unit mechanical tests. A comprehensive evaluation method for the effectiveness of dynamic compaction treatment on overburden was proposed by comparing and analyzing the in-situ density and pressuremeter modulus of the overburden before and after dynamic compaction to evaluate the reinforcement effect. The mechanical property indicators of the overburden after compaction were obtained. [Results] (1) The in-situ dry density in the shallow layers of Test Zone Ⅰ and Test Zone Ⅱ increased by 7.8% and 5.3%, respectively, after compaction, indicating that dynamic compaction significantly improved the in-situ density of the shallow overburden. (2) Within the upper 6 m, both the in-situ density and pressuremeter modulus of the overburden showed improvement. Below 6 m, the pressuremeter modulus remained close to pre-compaction levels. This demonstrated that dynamic compaction primarily enhanced the shallow layers of the overburden, with negligible reinforcement effects observed in deeper layers. [Conclusion] The proposed comprehensive evaluation method combines qualitative and quantitative assessment by comparing the pressuremeter modulus and in-situ density before and after dynamic compaction; together with laboratory unit mechanical tests, it can accurately obtain the mechanical parameters after compaction and provides an economical and efficient approach for assessing overburden treatment effects and engineering characteristics.