粗粒土应力诱导各向异性真三轴试验研究

使用河海大学最新研制成功的真三轴仪,对粗粒土进行不同主应力方向上的单向加荷试验。结果表明,在σ1、σ2、σ3方向上单向加荷时,加荷向变形都为压缩,而侧向变形较为复杂。当在σ1或者σ2方向上单向加荷时,σ3方向上都是发生膨胀,而另一个侧向(即σ2或σ1方向上)没有明显变形;当在σ3方向上单向加荷时,两个侧向(即σ1、σ2方向上)都几乎没有变形。分析认为:剪切作用增强即应力状态接近破坏面,会发生侧向膨胀;反之,剪切作用减弱,则无侧向膨胀产生或侧向膨胀较小。对σ3方向单向加荷的情况研究表明,该应力路径下,p、q、b这3个量的变化都是使试样的应力状态远离破坏面,剪切作用减弱,因此侧向膨胀很小或没有。所试验的粗粒土在一般应力条件下各向异性性质显著。

Quantitative modelling of granular soils considering density and pressure effects

The pile groups with complex structure or constructed in complex circumstances will be subjected to torque. It is of significance to study their bearing behaviors and to establish relevant calculation theory. According to the characteristic of rotation and load distribution in pile groups subjected to torque, an equation for determining the horizontal load and torque on each pile in the groups is established based on the force equilibrium conditions, and a method for determining twist center location of pile groups with asymmetrically horizontal rigidity distribution of piles is proposed. The coupling effect between piles and loads are analyzed based on recent researches. The method to calculate angle of twist of caps and loads distributed over each pile is obtained by introducing the p-y curve method and the torsion rigidity theory of a single pile. The relevant codes are programmed, and also employed to analyze centrifuge tests on a pile group, and the computed results are compared with the experimental results. The agreement is good. Finally, location offset of twist center of pile cap with asymmetrically horizontal rigidity distribution is analyzed, and some beneficial insights are provided.