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以土体抗剪强度规律在破坏面上归结为库仑定律,并同种各向同性土的三轴试验有效应力强度指标唯一存在为立论基础展开分析,通过建立不排水条件的库仑强度定律与三轴固结不排水剪切(CU)试验破坏时超静孔压的联系,对CU试验总应力强度指标线性存在的数学基础和物理意义进行了解析。结果表明:由排水和不排水条件下库仑强度规律的线性特征,可证明破坏面上与法向应力相关的孔压系数Df为常数;而CU总应力强度包线之所以线性存在是由于斯开普敦孔压系数Af能与Df、黏聚力及破坏时的偏应力建立起特定的数量关系,并明确提出了该关系的数学表达式。同时利用CU试验所得参数,求解了CU总应力割线强度指标R,cR的值。割线强度指标的确定为已定滑动面的工程问题提供更为合理和可操作的强度计算方法,而若选用切线强度指标,强度值可能会有10%以上的高估,带来极大的安全隐患。
Coulomb’s law is attributed to the law of soil shear strength on the failure surface, and the only effective indicator of the effective stress intensity in the same type of isotropic soil is the foundation of the theory. Based on the Coulomb’s law of strength with undrained conditions, Axis Consolidation undrained shear (CU) test when the ultra-static pore pressure link, the CU test total stress intensity index linear existence of the mathematical basis and the physical significance were analyzed. The results show that the pore pressure coefficient Df related to the normal stress on the failure surface is a constant by the linear characteristics of Coulomb’s strength law under both drained and undrained conditions. The reason why the total stress intensity envelope of Cu linearly exists is that the open The Cape pore pressure coefficient Af can establish a specific quantitative relationship with Df, cohesion and the deviatoric stress during failure, and the mathematical expression of the relationship is clearly put forward. At the same time, the parameters of CU test were used to solve the values of secant strength index R and cR. The secant strength index provides a more reasonable and operable method of calculating the strength of a given sliding surface engineering problem. However, if the tangent strength index is chosen, the strength value may be over 10% overestimated, resulting in a very large Security risks.