开挖条件下黏土中单桩竖向承载特性模型试验与分析

利用已有的离心机预固结加荷装置,开发了一套可以有效控制超固结比的模型桩竖向加荷系统,进行了开挖条件下饱和黏土中单桩竖向承载特性的室内模型试验。在模型试验用高岭土单元体试验的基础上,考虑开挖引起土体K0系数和不排水抗剪强度变化对桩侧极限摩阻力的影响,提出了开挖卸荷条件下饱和黏土中单桩竖向承载特性的非线性简化计算方法,并通过与模型试验结果进行对比验证了计算方法的正确性,算例分析表明:开挖将会使得竖向桩顶刚度和极限承载力的降低,合理的预测方法应该既要考虑开挖卸荷引起的桩侧土上覆压力的减少,又要考虑桩侧土体K0值和不排水抗剪强度的提高。     

Power induced by bubbles of different sizes and frequencies on to hollow fibers in submerged membrane systems

To shed light onto the relationship between sparging conditions and fouling control in submerged hollow fiber membranes, the effects of bubble size and frequency on the hydrodynamic conditions induced in membrane system were studied. Two general classes of bubbles were considered: coarse (0.75–2.5 mL) and pulse (100–500 mL). The power transferred (P_trans) onto membranes could be used to characterise the multiple effects induced under different sparging conditions. P_trans is proportional to root mean square of shear stress (τ_rms), the area of zone of influence (i.e. the fraction in the system where high velocity and high vorticity (turbulence) are induced by the bubble) and their rise velocity. At a given sparging rate, the power transferred onto membranes was less with coarse bubble sparging than pulse bubble sparging and increased with the size of pulse bubbles. For all cases, the power transfer efficiency was consistently higher for pulse bubble sparging than for coarse bubble sparging. The power transfer efficiency to the system was greatest for the small pulse bubbles considered when a small amount of power is required for fouling control. However, when fouling is extensive, large pulse bubbles may be required to generate the required amount of power for fouling control.     

考虑渗透吸力影响膨润土的修正有效应力及其验证

普遍认为膨润土是高放废物地质处置库缓冲/回填层的理想材料,膨润土在地下水溶液中的膨胀变形和剪切强度关乎高放废物地质处置库的安危。地下水溶液中膨润土膨胀变形和剪切强度受到渗透吸力影响,根据膨润土表面分形模型,建立考虑渗透吸力应力影响的修正有效应力公式,用竖向应力p和渗透吸力π表示为■,并采用膨润土在NaCl溶液中的膨胀变形和剪切强度进行验证。NaCl溶液中膨润土的膨胀变形与修正有效应力p~e表示为同一曲线■,峰值剪切强度与修正有效应力p~e表示为同一直线■,符合Mohr–Coulomb准则。