Experimental Study On Shear-Seepage Coupling Characteristics Of Structural Planes With Different Filling Degrees Under Osmotic Water Pressure

In recent years,with the increase of underground engineering,the seepage and accumulation of groundwater and sediment between structural planes have been aggravated,resulting in the weakening of shear resistance of structural planes and frequent accidents.Therefore,it is of great practical significance to study the shear-seepage coupling characteristics of structural planes with different filling degrees under osmotic water pressure.In this paper,similar material is used to replicate the structural plane,and the shear-seepage coupling characteristics of the structural plane under different filling degrees and different osmotic water pressure are experimentally studied by using the self-developed shear-seepage coupling device of coal and rock.Analyzing the mechanical properties and seepage characteristics,morphological characteristics and shear-seepage coupling characteristics of the structural plane.The main research results are as follows:(1)Under the shear-seepage coupling action,the shear stress-shear displacement curve of structural plane presents a peak type,which can be divided into two stages: elastic and plastic stages;The normal shear shrinkage occurs,and the change curve can also be divided into two stages: the normal displacement increases to a short-term constant and a continuous increase;The flow rate changes simply with the shear displacement,which shows that the flow rate keeps stable after the initial rapid growth to the peak value;The shear stress is consistent with the flow rate under displacement,but the flow rate will change when the normal displacement is at the turning point of the stage.(2)The influence of filling degree on shear seepage-coupling of structural plane under constant osmotic water pressure is discussed.The peak shear stress of structural plane decreases with the increase of filling degree;When there is no filling,the normal shear expansion of structural plane occurs;when there is filling,the normal shear shrinkage of structural plane occurs.The initial flow rate can be detected before the test starts,and increases with the filling degree increasing;When there is no filling,the peak flow rate of the structural plane is the largest,and the peak flow rate increases with the filling degree increasing;and the variation trend of shear stress and flow rate under the corresponding shear displacement is quite different;when there is filling,the influence of shear stress and normal displacement on flow rate decreases with the filling degree increasing;(3)The influence of osmotic water pressure on shear seepage-coupling of structural plane under constant filling degree is discussed.Peak shear stress of structural plane decreases with the increase of osmotic water pressure;The normal shear shrinkage still occurs after loading osmotic water pressure and decreases with the increase of osmotic water pressure.Peak flow of structural plane increases with the increase of osmotic water pressure,when osmotic water pressure is very small,and flow curve can be divided into three stages: initial flow change stage,flow increase to peak stage and basic stable stage.The flow curve only exists in the latter two stages when the seepage pressure increases.With the increase of osmotic water pressure,the influence of shear stress and normal displacement on flow rate decreases,and it is concluded that normal shear shrinkage occurs only when filling degree and osmotic water pressure act together.(4)Analyse the change of morphology before and after structural interview and the mechanism of shear-seepage coupling.With the increase of filling degree and osmotic water pressure,the three-dimensional morphology parameters increase,that is,the structural surface wear decreases gradually.Because of the fluctuation of the structural plane,the fissure opening changes in real time and the stress concentration occurs,the filling material will form one or two main fissures and become the main channel of seepage flow.With the increase of filling degree,the fractured part of filling material becomes larger.The boundary between the whole part and the fractured part is the diversion channel,and the erosion marks of the channel are obvious.