微生物加固钙质砂强度演化过程的环剪试验研究

Ring shear test study on strength evolution process of microbial reinforced calcareous sand

为获得钙质砂试样在微生物加固过程中的强度特性,对环剪仪的剪切盒进行改造,实现在环剪仪上直接完成钙质砂试样的微生物固化过程。通过环剪试验研究加固时间对固化效果的影响,考虑环剪试验过程中竖向应力的影响并与未加固钙质砂试样进行对比分析。结果表明:在改造后的环剪仪上直接完成固化可以获得加固时间较短、强度相对较低的试样。随着加固时间的增加,试样的抗剪强度不断增大并逐渐达到稳定值,加固48 h后,试样的抗剪强度及残余强度分别达到未加固试样的1.8倍及1.6倍。与未加固试样相比,固化试样表现出明显的应变软化现象,这可能与碳酸钙胶结结构发生破坏有关。在较高竖向应力(75~125 kPa)条件下,固化试样与未加固试样均会表现出较明显的应变软化现象,但两者出现软化现象的原因不同。

The reinforcement process was directly completed on the ring shear apparatus by remolding the shear box to reveal the strength characteristics of calcareous sandy samples during microbial treatment.The influence of treatment time on the curing effect was studied using ring shear tests.The effect of vertical stress was investigated.The results of treated samples were compared with those without treatment of calcareous sandy samples.The results showed that the treated samples with shorter treated time and relatively lower strength can be obtained utilizing completing the curing process on the modified ring shear apparatus directly.The shear strength of the treated samples increased and reached a constant with increase of treatment time.The shear strength and residual strength of the sample treated 48 hours could reach 1.8 times and 1.6 times of the values for untreated samples,respectively.Compared with the untreated sample,the treated sample shows obvious strain-softening behavior,which may be related to the destruction of the cemented structure of calcium carbonate.Under the condition of high vertical stress(75~125 kPa),both the treated and the untreated samples show an obvious strain-softening phenomenon,but the reasons behind this phenomenon are different.