Expansive soil-structure interaction and its sensitive analysis

Several groups of direct shear tests of Nanning expansive soil samples were carded out by improved direct shear apparatus. The results of the characteristics of the ultimate shear stress and residual shear stress at the interface of expansive soil-structure are presented as follows： linear relation can approximately reflect changes between the both shear stress and the three factors： vertical load, water content and dry density, just different degrees from each other; increasing the vertical load from 25 kPa to 100 kPa （up by 300%） can cause the average increase of ultimate shear stress from 58% （for samples with 1.61 g/cm^3） to 80% （for samples with 1.76 g/cm^3）, and an close average increase of 180% for the residual shear stress; increasing the water content from 14.1% to 20.8% （up by 47.5%） can cause the average decrease of the ultimate shear stress from 40% （for samples with 25 kPa） to 80% （for samples with 100 kPa）, and the average decrease from 25% （for samples with 25 kPa） to 30% （for samples with 100 kPa） for the residual shear stress; increasing the dry density from 1.61 g/cm^3 to 1.76 g/cm^3 （up by 9.3%） can cause the average increase of ultimate shear stress from 92% （for samples with 25 kPa） to 138% （for samples with 100 kPa）, and an average increase of 4% for the residual shear stress. Sensitive analysis was further made to explain reasons causing the differences of the both shear stress induced by the three factors.

LFR轴流式冷却剂主泵水力性能研究

为掌握铅铋介质在轴流式核主泵内的流动特性,通过计算流体力学(CFD)方法采用剪切应力输运(SST k-ω)湍流模型对铅铋介质和水介质进行瞬态数值计算,对比分析2种介质在叶轮和导叶计算域的能量变化及其规律。研究结果表明,工作介质雷诺数的改变对轴流式核主泵水力性能有明显影响,铅铋介质下主泵的扬程和效率均高于水介质。主泵在2种介质下理论扬程基本一致,但铅铋介质比水介质的实际扬程高出3%,表明2种介质差异主要体现在流动损失中;在对2种介质的水力损失形式的研究中发现,主泵在铅铋介质下的由摩擦引起的翼型损失小于水介质,并且铅铋介质的边界层分离点明显滞后。该研究可为LFR主泵水力设计提供一定参考。