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边坡稳定性分析时通常将应力条件简化为平面应变状态,采用三轴试验强度计算出的边坡稳定性偏于保守。在充分考虑中主应力物理含义及力学机制的基础上,将Mises屈服准则与Mohr-Coulomb(简称M-C)内切圆屈服准则进行匹配,得到了平面应变条件下土体屈服破坏时中主应力的理论修正关系,进而也得到了该条件下最大主应力与最小主应力的比值关系,从理论上证明了该比值关系是与土体平面应变破坏时内摩擦角成一定关系的常数,也在平面应变试验中得到了验证,从侧面反映出中主应力理论修正关系的合理性。由上述两种关系建立了土体平面应变破坏条件下的应力路径,结合Lade-Duncan强度准则,建立了平面应变条件下强度参数与三轴试验试验条件下强度参数转换公式,由该转换公式得到的平面应变条件下的强度参数与平面应变试验实测值误差在2%左右,大幅缩小了三轴试验实测值与平面应变试验实测值的误差。在均质边坡稳定分析中分别采用常规三轴试验强度值与由公式转换得到的平面应变强度值进行计算。研究结果表明,三轴试验条件下内摩擦角为10°~20°之间时,基于两种强度参数得出的安全系数相差不大;当三轴试验条件下内摩擦角大于20°时,平面应变条件下安全系数较三轴试验条件下提高19%左右,但该成果只在文中计算案例有效,两者误差的准确关系还有待于进一步研究。值得关注的是,由于平面应变条件下土体强度变大,边坡的临界滑面深度变浅了,其形态相应变陡。
In slope stability analysis, the stress conditions are usually simplified to the plane strain state. The slope stability calculated by triaxial test strength is conservative. On the basis of fully considering the physical meaning and mechanical mechanism of the middle principal stress, the Mises yield criterion is matched with the inscribed circular yield criterion of Mohr-Coulomb (MC), and the principal principal stress The relationship between the maximum principal stress and the minimum principal stress under this condition is also obtained. It is theoretically proved that the ratio relationship is a constant that is related to the internal friction angle at the time of plane strain failure of soil and is also in the plane Strain test has been verified, from the side reflects the theory of the correction of the relationship between the rationale for the main stress. The stress path under the plane strain failure of soil is established by the above two relations. Based on the Lade-Duncan strength criterion, the formula of the intensity parameter under the condition of plane strain and the strength parameter under triaxial test are established, and the formula Of the plane strain of the intensity parameters and the measured value of the plane strain test error of about 2%, significantly reducing the measured value of the triaxial test and the measured value of the plane strain test error. In the stability analysis of homogeneous slopes, the values of conventional triaxial tests and the values of plane strain strengths obtained from the formulas were calculated respectively. The results show that when the internal friction angle is between 10 ° and 20 ° under the triaxial test conditions, the safety factor obtained based on the two kinds of strength parameters shows little difference. When the internal friction angle is greater than 20 ° under the triaxial test conditions, Under the condition of plane strain, the safety factor is about 19% higher than the triaxial test, but the result is only valid in the paper. The exact relationship between the two errors needs to be further studied. It is noteworthy that, due to the soil under the condition of plane strain, the critical slip surface becomes shallow and the shape of the slope becomes steeper accordingly.