冲击碾压加固砂土模型试验研究

冲击碾压技术(IR)已在国内外公路、机场等工程的地基处理中得到大量应用，处理的深度明显大于传统静碾和振动压实技术，具有施工快速、节省工期和施工成本等优点，逐渐受到工程界和学术界的重视。关于冲击碾压技术的理论研究明显落后于工程实践，为进一步促进冲击碾压技术在工程中的合理应用，采用自行研制的冲击碾压模拟试验设备进行了模型试验研究，探讨冲击轮质量和牵引速度对冲碾加固效果的影响以及冲碾过程滚动冲击产生的冲击荷载形式和冲击能量在砂土中传递与衰减的过程。研究结果表明，冲击轮的质量和牵引速度对冲击碾压加固效果有明显影响，通过增加冲击轮质量可以明显增大土中浅层深度范围内的冲碾加固效果，牵引速度在冲碾过程中存在最佳值，接近最佳牵引速度时的冲碾加固效果最好；三边形冲击轮滚动冲击产生的冲击荷载为瞬变单脉冲形式，且在冲击接触面上不均匀分布，表现为接触面中心处冲击荷载较大而两侧明显较小；冲碾过程中冲击能量主要以瞬变非周期性脉冲形式在土体中传播，沿竖直方向传递，其衰减过程以负幂函数形式进行。

Model test of impact roller compaction for dry sand

Impact roller(IR) compaction has been widely used for ground improvement in highway, airport engineering at home and abroad. The IR applies high energy to the ground and densifies deeper than conventional static and vibrating rollers and has the virtues of saving construction period and cost. As a result, attentions from academic circles and engineering circles have been drawn gradually. However, the theoretical research of IR compaction technique is inadequate and far behind its engineering practice. To promote reasonable application of IR compaction technique, a laboratory study based on self-devised impact roller simulation device was carried out to investigate effects of mass of impact wheel and towing speed on the effectiveness of IR compaction. The impact load form and the transmission and attenuation of impact energy in dry sand during IR compaction were also investigated. The results of laboratory cone penetration tests show that both mass of wheel and towing speed have significant influence on the IR compaction effectiveness. The effectiveness of IR compaction is better when heavier wheel is used and can be increased significantly by increasing the mass of impact wheel. There is an optimum towing speed to achieve the best effectiveness of IR compaction. The results of stress measurement in tests show that the impact load is a transient single pulse and the load distribution is not uniform with higher values in the centre of impact contact area. It also can be found that the impact energy mainly transfers in vertical direction in form of transient single pulse and attenuates quickly in form of negative power function.