堆载和固结对高饱和度废弃黏土抗剪强度影响

Effect of dumping protocol and consolidation on shear strength of highly saturated abandoned-clay

以杭州某基坑开挖渣土为研究对象,开展了24组大尺寸固结-直剪试验,研究了瞬时、阶梯型和斜坡型3种加载方式下高饱和度黏土固结过程抗剪强度的变化规律.结果表明,在上覆荷载作用下,土体产生瞬时压缩,压缩量随荷载的增大而增加;在3种加载方式下,当最终荷载相同时,最终沉降量较为接近;剪切曲线为应变硬化型,初始切线模量和最终剪应力均随固结度或上覆荷载的增大而提高;加载方式对初始切线模量有一定影响,对最终剪应力影响较小;抗剪强度随固结度的增长呈线性增大趋势,增大幅度随荷载的增大而显著;在3种加载方式下,当上覆荷载和固结度相同时,抗剪强度基本接近.基于试验结果,建立了高饱和度黏土固结过程抗剪强度预测模型,并利用本文试验数据和文献数据验证了其可靠性.模型分析结果表明:随着固结度的增长,抗剪强度包络线截距呈线性增大,而弯曲程度呈线性减小.在高饱和度废弃黏土堆填工程中,可采用本文建立的模型来预测不同堆填方式下土体固结过程的抗剪强度.

In this paper,24 sets of large-scale combined tests of consolidation and direct shear were conducted on the representative abandoned-soil samples that obtained from a foundation engineering site in Hangzhou.They were performed to investigate the shear strength behavior of highly saturated clay during consolidation under three loading protocols of instantaneous,stepped and linear stress.The results show that:the highly saturated clay had immediate compression after the application of overburden stress and the compression increased with an increase in the stress;when the final stresses of three loading protocols were the same,the final settlement was relatively close;the shear curves were strain hardening,and the initial tangent modulus and final shear stress both increased with the increase of consolidation degree or overburden stress;the loading protocol had a certain effect on the initial tangent modulus,but had a smaller effect on the final shear stress;the shear strength increased linearly with the growth of consolidation degree,and the magnitude of increase was significant with increasing stress;when the overburden stress and consolidation degree were consistent,the shear strength was essentially similar under three loading protocols.Based on the above findings,a shear strength prediction model of highly saturated clay considering consolidation was established and its reliability was verified using the data from this study and relevant literature.The model analysis results show that:with the growth of consolidation degree,the shear strength envelope intercept increased linearly,while the bending degree decreased linearly.In the highly saturated abandoned-clay dumping projects,the model established in this paper can be used to predict the shear strength of the soil under consolidation process of different dumping protocols.