The Study Of Permeability Characteristics And Permeability Stability Of Surrounding Rock Of Underground Powerhouse Groupof Xinjiang Fukang Pumped Storage Power Station In Construction Period

As the scope of water resources and hydropower engineering construction gradualiy expand,many pumped storage power stations build across the river,the underground cavern group have the characters of large buried depth,high groundwater head,and general below the groundwater level.Under the condition of the complex geological environment,the excavation process of underground cavern surrounding rock stability,the surrounding rock of underground cavern permeability,the coupling characteristics of stress field andthe study of permeability control measures,is an important guaranty for the long time save and stable operation underground.The article propose Fukang pumped storage power station underground cavern buried deep lithologic mainly carboniferouswhichwere bedded siliceous sandstone,conglomerate and intrusion of diabase stratum mountain which is in the left bankof Baiyang River.Permeability stability of rock mass and permeability prevention messure under the conditions of complex,anisotropicpermeability characteristics of surrounding rock,is the one of the main engineering geological problems in the workshop.For this type of pumped storage power station in line with the group of engineering construction of underground cavern is of effective guidance,in this paper,the main results are:(1)There are 32 partsof surrounding rock groundwater with water infiltrating-water dripping state in main cavernPD30.the groundwater in the other parts and other caverns is in the state of moist-damp;most of the water infiltrating-water dripping parts develop inrock mass of alternating layers(rock mass of Mosaic structure),or rock mass of thick layers(rock mass ofmassive structure),but A handful of develop in thick rock mass ofbedded structure(rock mass ofblock structure).(2)Cavern group is basically in the micro porous layer,permeability of rock mass overall < 1 Lu.Permeability coefficient is mainly the 10-8m/s,anisotropic permeability characteristics of rock mass in study area is obvious,Ky/Kz is about 2.67 times,and Kx/Kz about 2 times.(3)The natural condition of the permeabilityfield in the study area is much fit with the actual situation,affected by the excavation and anisotropic permeability characteristics of caverngroup,the porous flow field finally formed the shape of elliptic spherical funnel with the big area of x?y,but small area of z;after permeability blocking,permeability field gradually restore the natural state in five years.(4)Using the Geo-slope to simulate stress field-porous flow field after underground powerhouse group excavation shows that,deformation of the surrounding rock is mainly the shear damage,but a small amount of tension damage;Using the Visual MODFLOW to simulate permeability shows that,the effect of permeability prevention used by a combination of drain hole and diaphragm wall is best.(5)The evaluation of the permeabilitystability of surrounding rock under permeabilitycontrol measures conditions show that,with the groundwater in factory area drained out,total stress drops,plastic deformation range of surrounding rockobviously decreases,and it is conducive to the stability of surrounding rock.