径向围压条件下的砂粒流失特性试验

Experiment on Sand Loss Characteristic Under Radial Confining Pressure Condition

针对径向围压条件下砂粒流失问题,通过自行研制的三轴砂粒流失试验装置,研究压实系数、水力梯度和破损口直径对砂粒流失机理和渗透性演化规律的影响.试验结果表明:在不同压实系数、水力梯度和破损口直径条件下,砂粒流失均可分为无流失阶段、快速流失阶段及稳定流失阶段;在高压实系数条件下,流水体积均可分为缓慢发展阶段与快速发展阶段,并且存在短暂堵塞阶段,而在低压实系数条件下,流水体积基本不存在缓慢发展阶段和短暂堵塞阶段;砂粒累计流失率基本上随压实系数的增大而减小,随水力梯度的增大而增大,但随着破损口直径增大,压实系数对砂粒流失的影响减小,同时,随着压实系数增大,水力梯度对砂粒累计流失率的影响减小.

Aiming at the problem of sand loss under radial confining pressure condition,through the self-developed triaxial sand loss test device,the effects of compaction coefficient,hydraulic gradient and diameter of damaged orifice on sand loss mechanism and permeability evolution law were studied.The test results show that the sand loss can be divided into no loss stage,rapid loss stage and stable loss stage under different conditions of compaction coefficient,hydraulic gradient and diameter of damage orifice.Under the condition of high compaction coefficient,flow volume can be divided into slow development stage and fast development stage,and there is a transient plugging stage.Under the condition of the low compaction coefficient,there is no slow development stage and no transient plugging stage in flowing water volume.The cumulative sand loss rate basically decreases with the increase of compaction coefficient,increases with the increase of hydraulic gradient.With the increase of diameter of damaged orifice,the influence of compaction coefficient on cumulative sand loss rate decreases.With the increase of compaction coefficient,the influence of hydraulic gradient on cumulative sand loss decreases.