结构性软土的黏滞系数

Viscosity coefficient of structural soft clay

黏滞系数是表征土的蠕变和流动特性的重要指标。对黄石、漳州、青岛地区结构性软土进行电子显微镜扫描、颗粒分析、X衍射试验和化学分析试验,测试结果表明,软土的粒度成分、矿物成分、物理化学性质、结构类型对黏滞系数影响较大。软土蠕变过程中,结构单元体发生定向排列或产生滑动,其相对运动使结合水的黏滞性反映出来,进而引起黏滞系数的变化。进行直接剪切蠕变试验,并通过陈氏法处理蠕变试验数据。试验结果表明,黏滞系数随剪应力的增加达到峰值,固结压力越大,峰值体现越明显,峰值对应的剪应力也越大,这主要是微观结构随剪应力增大逐渐破损所引起的。固结压力增大,结合水膜厚度变薄,土颗粒间连接力增强,黏滞系数也随之增大。用不同固结压力下黏滞系数峰值对应的剪应力代替临界抗剪强度,提出了一个新的求取长期强度的方法,并通过试验数据验证了方法的正确性。该研究有助于进一步认清蠕变机制,对修正或建立较为符合实际的本构模型有一定意义。

The viscosity coefficient is a key parameter which expresses the soil creep and flow characteristics.Electron microscope scanning,particle size analysis,X-ray diffraction and chemical analysis test of Huangshi,Zhangzhou and Qingdao areas soft clays are performed.The test results show that soft clay’s granulometric composition,mineral component,physicochemical properties and structure type influence the viscosity coefficient remarkably.In the soft clay creep process,the structure haploid had the directional arrangement or had the glide,its relative motion caused the bound water viscosity to reflect that then caused the viscosity coefficient change.The direct shear creep test is carried out and using Chen method to process creep test data.The test results show that because the microscopic structure increases along with the shearing stress damages gradually;the viscosity coefficient increased along with the shearing stress achieved the peak value,a consolidation pressure bigger peak value manifests is more obvious;the peak value correspondence＇s shearing stress is also bigger.A new seeking long-term strength method which the viscosity coefficient peak value correspondence＇s shearing stress replaced the critical shearing strength with the different consolidation pressure is proposed,and confirmed the accuracy of this method through the tentative data.The test results make contribution to understanding the creep mechanism and that the constitutive model can be set up according to the actual engineering.