水泥土芯样强度变形特性及本构关系试验研究

An experimental study of strength and deformation properties of cemented soil core sample and its constitutive relation

为了研究现场施工工艺下水泥土的强度及变形特性,对水泥搅拌桩钻孔芯样进行了无侧限抗压强度试验与三轴试验,分析了水泥掺量与围压对水泥土芯样强度、变形特性的影响规律。结果表明:随着水泥掺量的提高,水泥土芯样的强度明显增强,变形模量显著增大,但其破坏应变变小,脆性增大;水泥掺量超过18%的水泥土芯样其应力-应变关系表现为软化型,随着围压的提高,其强度增强,破坏应变增大,脆性降低,且应力-应变关系曲线有可能发生转型;不同围压下的水泥土芯样三轴试验先为体缩,后变化为体胀,发生剪胀的应变较破坏应变略小,是由剪切面上颗粒错动引起的,在颗粒错动达到一定程度后抗剪强度才发挥到峰值;水泥土的结构屈服应力比较大,在围压的作用下其胶结结构未发生破损,强度包线满足摩尔-库仑线性强度规律;根据水泥土的强度变形特征,应力-应变全曲线分弹性、塑性、软化3个阶段,可采用Popovics模型对其进行模拟,与试验结果较为吻合。

Consolidation drained triaxial compressive tests and unconfined compression strength tests were carried out on cement-mixed pile core samples to study the strength and deformation properties of the cemented soil on-site construction process. The effects of confining pressure and cement content on strength and properties of cement-mixed pile core samples are investigated. It is observed that with increasing the cement content, the strength, deformation modulus and the fragility of the cemented soil core samples obviously increase, but the failure strain decreases; when the cement ratio is more than 18%,the stress-strain relationships of the samples show softening; and with increasing cell pressure, the strength and destruction strain increase, the friability decreases, and the stress-strain curves may transform in the form. The behaviors of the samples all firstly exhibit a volumetric shrinkage and then a dilatancy under different confining pressures. in the consolidation drained triaxial compressive tests. And the dilatation-induced strain is slightly smaller than the failure strain. The dilatancy is caused by moving of particles. Only the particles moving reach a certain extent,the shear strength can develop up to a peak. Because the cemented soil has larger structural yielding stress, its cementation structure is not damaged under confining pressures, and its strength envelope meets Mohr-Coulomb linear rule. According to the strength and deformation properties of cemented soil, its complete stress-strain curve can be divided into three stages of elastic, plastic, softening. Popovics model is used to simulate the stress-strain relationship of cemented soil core sample, which shows that the calculated results agree well with the experimental results.