球(柱)孔扩张问题的扩孔压力与扩孔半径分析

为研究无黏性土中沉桩扩孔和静力触探试验等岩土工程问题,采用Tresca准则对球(柱)孔扩张问题的扩孔压力和扩孔半径关系进行理论分析。以圆孔扩张理论为基础,利用弹塑性交界面处的边界条件建立平衡方程,推导出球(柱)孔扩张问题中塑性区半径rp与扩孔压力p和扩孔半径a的关系,并结合孔周土体体积变化规律,得到了初始半径a0、扩孔半径a和对应的扩孔压力p三者之间的理论关系;同时为判断孔周围土体是否进入弹塑性状态,确立了可由扩孔半径a判定的公式。此外,基于上述理论公式推导出了不排水条件下球(柱)孔扩张的应力场、位移场和扩孔压力极限值pu。分析结果表明:同一初始状态下,扩孔压力p随初始半径a0与扩孔半径a的比值而变化;且塑性区半径rp仅与扩孔半径a的变化有关;当扩孔半径a大于某一定值时孔周土体进入弹塑性状态。最后通过算例分析,对球(柱)孔扩张中应力场和位移场分布、塑性区半径、扩孔压力以及扩孔压力极限值的变化规律进行了分析。

Theoretical analysis of expanded radius and internal expanding pressure of the spherical(cylindrical) cavity expansion

Through the preloading on the concrete specimen,the internal propagation velocity of elastic waves and the compressive strength between initial state and failure state can be measured,then the relationship between the reduction of elastic wave velocity and deterioration of compressive strength can be researched.The research shows that the increase of the number of main peaks and the extension of the reflection signal period of the bottom boundary surface can be used as the basis for the identification of damage in the MEM superior cycle diagram.Elastic wave velocity has a good correlation with the damage degree inside concrete,the greater the damage degree of concrete,the greater the reduction value of wave velocity.According to the experimental data between the linear correlation with the decrease of elastic wave velocity and the deterioration of compressive strength,a linear equation is fitted.It is possible to detect internal damage to the concrete in the impact echo,and the reliability and safety analysis of concrete structures has a broad application prospect.