黏性土非线性弹性K-G模型的一种改进方法

A modified method of nonlinear elastic K-G model for clay soils

为解决《土工试验规程》建议的K-G模型未考虑土体剪缩性问题并保持其简单性,在其基础上增加了一个剪缩模量,建议了一个3模量7参数K-G-D模型,给出了用p和q与εv和εs表示的完整的增量应力应变关系式;通过正常固结黏土的各向等压固结试验和等平均正应力的三轴压缩排水试验标定了模型参数;进行了黏土的常规三轴压缩排水试验,利用模型参数预测了相应路径下土样的体积与轴向变形,经与实测值对比,预测结果较好。该模型可考虑土体压硬性、剪缩性、应变强化特性,能较完善地描述欠固结和正常固结土及松砂和中密砂在等p和增p路径下的变形特性;模型并未在规程模型的基础上增加试验工作,且概念清晰、形式简单、便于实际应用。

In order to solve the problem of reckoning without shear contraction in K-G model suggested by Specification of Soil Test and keep its simplicity, a shear contraction modulus is proposed and a three-modulus modified K-G-D model is suggested which has seven parameters; the integrated incremental stress-strain relations are expressed by mean normal stress, generalized shear stress, volumetric strain and generalized shear strain are given. Model calibration for normal consolidated clay soil is carried out by isotropic consolidation tests and drained triaxial compression tests that the mean normal stress remains constant, model verification is carried out by the drained conventional triaxial compression tests, the computation results by the model parameters coincide well with curves of the tests, which demonstrates that the modified method is rational and applicable. The modified model is capable of reflecting the characteristics of pressure sensitivity, shear contraction and strain hardening, and suitable to underconsolidated and normally consolidated clay soils, loose and medium sands under the stress paths of mean normal stress increasing or remaining constant. In addition, the model calibration does not need additional tests, the modified model is clear in concept, simple in form and convenient to use.