The evaluation of the hydraulic properties evolution of granular sandstones in relation with groundwater inrush within faults is an important issue for mining engineering applications. This paper presents the results of an experimental investigation of small particle migration from granular sandstone samples under different original porosities, particle size compositions and water flow pressures. A new rock testing system has been setup to carry out the tests. Based on the results, it is observed that the overall permeability evolution during the tests can be divided into four different phases, including i) re-arrangement of large rock fragments, ii) water inrush with substantial particle migration, iii) continued moderate particles seepage, and iv) steady state water flow. The crushing of edges and corners of large rock fragments, and the evolution of the fracture network has mainly been observed in the first two phases of the tests. The results indicate that the migration of small particles has an essential effect on permeability and porosity increase during water inrush through fractured sandstone. The samples with higher original porosity, higher percentage of fine particles in their formation and under higher water flow pressures, achieve higher permeability and porosity values when the test is complete. Furthermore, using the measured data, the performances of a number of empirical models, for permeability evolution in fractured porous media, have been studied. The prediction results indicate that not all of the fractures in a sample domain contribute in small particle migration. There are parts of the fracture network that are not effective in particle flow, a sample with less original porosity, more fine particles and under lower water pressure shows less ineffective fractures. Therefore, using the concept of the effective porosity (fracture) is sufficient enough for the flow calculation.\ud\ud
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机译：对于断层内部的地下水涌流，评估粒状砂岩的水力特性演化是采矿工程应用中的重要问题。本文介绍了在不同的原始孔隙度，粒度组成和水流压力下，颗粒状砂岩样品中小颗粒迁移的实验研究结果。已经建立了新的岩石测试系统来进行测试。根据结果，可以观察到测试过程中的总渗透率演变可分为四个不同阶段，包括：i）大块岩石碎片的重新布置，ii）大量颗粒迁移的涌水，iii）持续的中等颗粒渗漏iv）稳态水流。在测试的前两个阶段中，主要观察到了大块岩石碎片的边角和角的压碎以及裂缝网络的演化。结果表明，小颗粒的迁移对裂缝性砂岩的注水过程中的渗透率和孔隙度的增加具有至关重要的作用。当测试完成时，具有较高原始孔隙率，较高百分比的地层中细小颗粒和较高水流压力的样品可获得较高的渗透率和孔隙率值。此外，使用测得的数据，已经研究了用于破裂多孔介质中渗透率演化的许多经验模型的性能。预测结果表明，并非样品域中的所有裂缝都有助于小颗粒迁移。裂缝网络中的某些部分对颗粒流动无效，样品的原始孔隙率较低，更多的细颗粒且在较低的水压下显示较少的无效裂缝。因此，使用有效孔隙率（断裂）的概念足以进行流量计算。\ ud \ ud
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