In Situ Experimental Study Of Permeability On Fault Zone

The complete granite rock mass has extremely low permeability.However,there are many fractures near the fault zone.Granite rock mass near the fault core is broken up,which makes the rock mass with high permeability.High level radioactive waste disposal repository has a high requirement for the closure of the nuclear.Because of the existence of the fault zone,it is likely to become a potential channel for the migration of radionuclides in the future,the potential threat to the construction of nuclear waste disposal repository.Study on the permeability of fractured rock mass affected zone in the fault zone has important directive significance to the location and construction of nuclear waste disposal repository.There are many methods for obtaining permeability of rock mass,such as laboratory test and simulation test.However these test has some limitations,such as laboratory tests often require sampling,transportation,processing,such as a series of processes,in the process more or less will have a certain effect of original rock structure and stress condition.Coupled with the sampling and transport process of many restrictions,can be carried out in the fracture rock mass test sample size is small,therefore,the test results tend to have a high dispersion,and the actual permeability of the rock mass difference.Water pressure test and tracer test between holes are in situ tests to avoid sampling,transportation,processing process.Therefore,original rock structure and force condition has little effect,and we can get real reflect the permeability characteristics of the study area of rock fracture.In this paper,the test of borehole water pressure is used to test the rock mass of the Shiyuejing fractured zone.The fractured granite rock drilling and for water machine in the prior art can not be fixed and portable rig in a complete hard rock drilling problems often encountered in the core root cutting difficult to smooth out.A water drilling rig used in fractured rock mass is developed,which is suitable for the test and sampling device used in fractured rock mass,so as to solve the problem of drilling and coring in fractured rock mass.Borehole pressure water test using embolism will be drilled at one end or both ends of the plug,you can isolate a certain length of the test section,and obtained the relationship between flow rate and time under stable pressure.The P-Q pressure curve of the rock mass in the fracture zone of the well is basically coincident,and the curve is raised to the Q axis,which can be considered to be basically in line with the characteristics of turbulent flow.According to the research of fracture equivalent hydraulic aperture and fracture density,we can calculate the permeability coefficient of the footwall rock at different positions.Several drilling holes were arranged at different distances from the main section of the fault.The water pressure test and tracing test were carried out to obtain the permeability coefficient of rock mass at different locations of the main section.By main section distance and rock mass permeability coefficient curve analysis distance closer to the core of the fault rock crack density high,permeability coefficient is generally greater than 1×10-6m/s and obtained by the test of rock mass permeability dispersion coefficient is relatively low can think near the fault core has certain heterogeneity.As far away from the main fault section of rock mass permeability decreases,obtained by the test of rock mass permeability coefficient larger discreteness,known from the distant section of the fault rock small scale permeability test and can not represent the fractured rock mass permeability should consider the use of more large scale in-situ permeability test.According to the tracer test time,pressure head and hole spacing information,it is assumed that the seepage only by single fracture can be obtained fracture equivalent hydraulic aperture;by of fractured rock Photogrammetry for fracture in different position of gap width value,the crack width statistics analysis and calculation can be obtained fracture and the equivalent hydraulic aperture.Comparative analysis of test methods for synthesis of various Jijicao,determine the equivalent hydraulic aperture range.