Study On The Deformation Of Broken Rocks Under Stress And Water-sediment Seepage

Mining rock mass water-sand seepage characteristics study is an important topic pertinent to coal mine safety. The structure of rock mass may be destroyed due to mining activities and the broken rock masses will often bear confining pressure. This article is to introduce a pressurized permeability test device compatible with the loading equipment and designed to study the deformation and water-sand seepage characteristics of broken rock mass under the action of stress, and to describe the following innovative achievements so far made:(1) In order to study the broken rock deformation and water-sand seepage characteristics under the action of stress, a pressurized permeability test device compatible with the loading equipment has been developed independently. The device is able to cause rheological deformation of broken rock mass so as to study the water-sand seepage characteristics of the deformed broken rock mass. The pressurized permeability test device is able to mimic the process of rheological deformation of the broken rock mass under confining pressure where the broken rock mass and sand come separate in different layers and the sand, stirred by water flow and mixed with water, crushes into the broken rock mass. This test is able to provide reference for similar tests and future extended studies.(2) The effects of different stress levels and size grading on rheological properties and water-sand seepage characteristics of broken rock mass have been studied using the self-developed water-sand seepage testing system for broken rock mass under the action of stress. In the course of compaction and rheological deformation, broken rock mass undergoes constant changes in such parameters as elasticity modulus and viscosity coefficient. According to the broken rock mass rheological test result and based on fractional calculus theory and the broad sense of Kelvin rheological model, fractional Abel dashpot has been introduced to substitute Newton dashpot, create a new fractional rheological model and deduce the three-dimensional creep constitutive equation of rock under the action of constant stress; and the effect of seepage on the creep properties of rock has been analyzed.(3) In the course of water-sand seepage of broken rock mass, some of the sand is held back after flowing into the broken rock mass, occupies part of the space and changes the porosity of the broken rock mass. This article also works out the relationship between original porosity and seepage coefficient for seepage of broken rock mass with different size grading and in different fluid; and the curve relation between the sand inrush and filtering capacity and original porosity of broken rock mass with different size grading. Apply stress loading(rheological deformation) and direct compressive loading to broken rock mass and cause it to suffer compressive deformation so as to study the effects of different loading methods on the water-sand seepage characteristics of broken rock mass.(4) If water-sand seepage occurs within broken rock mass, not all sand can go through the broken rock mass in certain cases. The sand filtering function of the broken rock mass will result in change in the skeleton property of the broken rock mass, making such function an important factor influencing the seepage properties of the broken rock mass. Based on the test result, the screen layer model of broken rock mass taking seepage process into consideration has been brought forth, the relationship between the equivalent thickness and original porosity studied, and the suggested computational formula given; numerical simulation of water-sand seepage of broken rock mass has been carried out based on particle flow code(PFC). This may provide reference for the prediction of water-sand seepage disaster of broken rock mass.