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861.
To simultaneously take into account the Biot-flow mechanism, the squirt-flow mechanism, and the frame-viscoelasticity mechanism, a generalized viscoelastic BISQ (Biot/squirt) model is developed for wave propagation in clay-bearing sandstones based on Dvorkin's elastic BISQ model. The present model is extended to a wide range of permeabilities (k 〉 0.05 mD) by introducing a dimensionless correction factor for viscoelastic parameters, defined as a function of the permeability and the clay content. We describe the frame's stress-strain relationship of the clay-bearing sandstones by the differential constitutive equations of generalized viscoelasticity and then derive the viscoelastic-wave dynamic equations. With the assumption of a plane-wave solution, we finally yield the phase velocities and the attenuation coefficients by solving the dynamic wave equations in the frequency and wave number domain. The comparison of numerical results and experimental data shows that the generalized viscoelastic BISQ model is applicable for modeling the wave propagation in most of the sandstones mainly bearing kaolinite clay. 相似文献
862.
863.
桩-土相互作用影响的模型试验研究 总被引:5,自引:2,他引:3
通过将模型试验、现场实测的结果与弹性理论解进行对比,指出弹性理论解夸大了桩-桩、桩-土、土-土相互作用影响,造成沉降计算值偏大和过高估计桩顶反力的不均匀性(或筏底地基土反力的不均匀性),并提出对弹性理论解进行修正的途径和方法。 相似文献
864.
865.
超长灌注桩桩身压缩综合系数反分析 总被引:5,自引:1,他引:4
基于超长桩现场试验和数值模拟资料,通过反分析得出了桩身压缩的综合系数,进而对综合系数与其他参数的关系曲线特点、综合系数的影响因素、综合系数的回归预测等进行了研究。结果表明:(1)极限状态下超长灌注桩的综合系数的变化范围为0.278 5~0.988,规范法中取定值0.5或1.0的做法是不合理的。(2)综合系数总体上随桩顶荷载、桩身压缩、桩身总位移、桩身刚体位移的增大而增大,但关系曲线型式存在多样化。(3)超长桩综合系数与长径比的相关关系不明显,但总体来说,综合系数随长径比的增加而降低。对超长嵌岩桩,不同场地桩的综合系数与长径比相关关系较好;对超长非嵌岩,不同场地桩的综合系数与长径比相关关系不明显,但对某场地5根桩,综合系数与长径比的指数相关关系达到0.990 1。(4)总的来说,持力层与上覆土层弹性模量比小的桩的综合系数-桩顶荷载曲线在弹性模量比大的上方。(5)建立的6个场地多根桩的综合系数与桩顶荷载关系的回归曲线的相关系数平均为0.977 6,可为该场地及类似场地桩的桩身压缩综合系数的预测和计算提供参考。 相似文献
866.
867.
A number of slope failures during the 2004 Niigataken Chuetsu earthquake were investigated, revealing that the travel distance becomes longer as the slope gets gentler and the failed soil mass gets larger. An energy-based approach, proposed in previous research to evaluate the travel distance of failed slopes, is modified by adding the model test results and introducing a simple evaluation method. The energy approach is then applied to a number of slopes failed during the earthquake to back-calculate mobilized friction coefficients, revealing their strong dependency on initial slope inclinations. The friction coefficient was found to be smaller than the initial slope inclination for gentler slopes, indicating that the failed soil mass tends to accelerate. In contrast, that for steeper slopes was higher than initial slope inclination. The friction coefficient was found to decrease with increasing volume of failed slope, which is quite consistent with previous case studies including large non-seismic landslides. 相似文献
868.
869.
开发导致的时移地震差异代表了油藏的岩石物理性质变化,本文从差异波形角度出发,明确了声波阻抗界面的反射系数与油层声波阻抗变化之间的函数关系,进而分析薄油层时移地震差异波形特征.通过分析得出,开发前后油层阻抗变化越大,时移地震的差异振幅幅度越大;薄油层的差异波形特征仅与油层的声波阻抗变化有关,油层声波阻抗增大导致与地震子波微分形式相同的差异波形,油层声波阻抗减小产生的差异波形与180°相位的地震子波微分形式相同;油层声波阻抗变化方向导致差异波形振幅幅度变化的快慢. 相似文献
870.
David Ching-Fang Shih Yue-Gau Chen Gwo-Fong Lin Yih-Min Wu 《Stochastic Environmental Research and Risk Assessment (SERRA)》2009,23(5):613-620
It is evident that the hydrodynamic dispersion coefficient and linear flow velocity dominate solute transport in aquifers.
Both of them play important roles characterizing contaminant transport. However, by definition, the parameter of contaminant
transport cannot be measured directly. For most problems of contaminant transport, a conceptual model for solute transport
generally is established to fit the breakthrough curve obtained from field testing, and then suitable curve matching or the
inverse solution of a theoretical model is used to determine the parameter. This study presents a one-dimensional solute transport
problem for slug injection. Differential analysis is used to analyze uncertainty propagation, which is described by the variance
and mean. The uncertainties of linear velocity and hydrodynamic dispersion coefficient are, respectively, characterized by
the second-power and fourth-power of the length scale multiplied by a lumped relationship of variance and covariance of system
parameters, i.e. the Peclet number and arrival time of maximum concentration. To validate the applicability for evaluating
variance propagation in one-dimensional solute transport, two cases using field data are presented to demonstrate how parametric
uncertainty can be caught depending on the manner of sampling. 相似文献