土钉支护的离心模型试验研究

土钉由于其施工简便、经济高效,已做为原位土体加固和支护技术被广泛应用。但是对于土钉加固机理的了解还有待于深入研究。中国建筑科学研究院地基所和清华大学共同完成了土钉支护机理的离心模型试验研究。采用清华大学中型土工离心机进行了8组土钉支护基坑的离心模型试验。离心模型试验研究表明,土钉能够显著提高基坑土体的稳定性。土钉长度和密度对支护基坑土体的稳定性影响非常显著。在本文所研究的土性和基坑条件下,当土钉最大长度和基坑高度之比(L/H)为0.48和0.8时,基坑土体基本不会发生整体剪切破坏。土钉支护土体发生外部整体剪切破坏的条件是高密度布置短钉情况,土钉支护土体发生内部钉筋拔出破坏的条件是稀疏布置长钉情况。

Centrifuge modeling of soil nail reinforcements

Soil nailing has been widely used as an in situ reinforcement technique as it is easy to implement and cost effective. However, the reinforcement mechanism is still poorly understood. A centrifuge study of soil nail reinforced cuttings was carried out jointly by the China Academy of Building Research and Tsinghua University. Results of eight tests performed on the centrifuge at Tsinghua University show that soil nailing can greatly increase the stability of the cuttings. The length and density of soil nails have significant effects on the behavior of the nailed structure. When the ratio between the maximum nail length to the excavation depth (L/H) was 0.32 or 0.34, the model slope was unstable. However, when the L/H ratio was 0.48 or 0.8, the models were substantially stable against global failure. External failure mode occurred in nailed structures with densely reinforced shorter nails, whereas internal failure or pullout of nails occurred in nailed structures with sparsely reinforced longer nails.