CAJ | 학술논문

深厚软黏土的大变形特性以及土中渗流存在的起始水力坡降已分别为人们所认识，但能考虑起始水力坡降的深厚软土大变形固结理论报道甚少。假定土的体积压缩系数保持不变，渗透系数与孔隙比为平方关系，在拉格朗日坐标系中建立以超静孔隙水压力为变量考虑起始水力坡降的软土大变形固结问题的控制方程及求解条件。利用有限差分法解决了由起始水力坡降所引起的动边界问题，将很小起始水力坡降下(10－5)的差分解与达西渗流定律下解析解对比，验证了差分数值计算结果的可靠性，从而为解决移动边界问题提供了一种有效方法。最后着重分析了量纲一变量R对固结性状的影响及在大、小应变不同几何假定下固结性状的区别，结果表明：R值的大小会影响渗流前锋的最终位置及移动速度、超静孔压的消散速率。R值越大，渗流前锋的移动速度越慢，土中超静孔压消散越慢，残留于土中而不能消散的超静孔压越大，进而导致土体发生的最终沉降量就越小。大变形几何假定下土中超静孔压的消散速率要比小变形几何假定下快，且固结完成时残留于土中不能消散的超静孔压值要比小变形几何假定下小，故计算得到的地基最终沉降量要比小变形几何假定下的计算值大。
심후연점토적대변형특성이급토중삼류존재적기시수력파강이분별위인문소인식，단능고필기시수력파강적심후연토대변형고결이론보도심소。가정토적체적압축계수보지불변，삼투계수여공극비위평방관계，재랍격랑일좌표계중건립이초정공극수압력위변량고필기시수력파강적연토대변형고결문제적공제방정급구해조건。이용유한차분법해결료유기시수력파강소인기적동변계문제，장흔소기시수력파강하(10－5)적차분해여체서삼류정률하해석해대비，험증료차분수치계산결과적가고성，종이위해결이동변계문제제공료일충유효방법。최후착중분석료량강일변량R대고결성상적영향급재대、소응변불동궤하가정하고결성상적구별，결과표명：R치적대소회영향삼류전봉적최종위치급이동속도、초정공압적소산속솔。R치월대，삼류전봉적이동속도월만，토중초정공압소산월만，잔류우토중이불능소산적초정공압월대，진이도치토체발생적최종침강량취월소。대변형궤하가정하토중초정공압적소산속솔요비소변형궤하가정하쾌，차고결완성시잔류우토중불능소산적초정공압치요비소변형궤하가정하소，고계산득도적지기최종침강량요비소변형궤하가정하적계산치대。
Threshold gradients and large deformation of thick soft soil may have been realized by researchers. However,the theory of large strain consolidation of soft clay with threshold gradient has rarely been reported. Supposing the constant coefficient of volume compressibility and the square relationship between coefficient of permeability and void ratio,the governing equation and solution conditions of large strain consolidation of soft clay with threshold gradient are developed in Lagrangian coordinates,in which excess pore water pressure serves as a variable. Finite difference method is adopted to obtain the solution for the problem of moving boundary which is induced by threshold gradients,and the reliability of numerical results is verified by comparing the numerical solutions under tiny threshold gradient(10-5) with analytical solutions in case of Darcy′s flow law. Thus,an effective method is provided to solve the problem of moving boundary. Finally,the influence of dimensionless variableR on consolidation behavior and the difference of consolidation behavior between large-strain and small-strain assumptions are analyzed,and the results show that the value of dimensionless variableR influences the final flow front location,the moving rate of flow front location and the dissipation rate of excess pore water pressure. The larger the value ofR is,the slower the moving rate of flow front location is,and the slower the dissipation rate of excess pore water pressure is. The larger the value ofR is,the larger the residual excess pore water pressure is, and the less the final settlement of soil layer is. The dissipation rate of excess pore water pressure with large-strain assumption is faster than that with small-strain assumption;furthermore,the residual excess pore water pressure with large-strain assumption is less than that with small-strain assumption. This consolidation behavior results in that the final settlement of foundation with large-strain assumption is larger than that with small-strain assumption.