Prediction And Prevention Of Water Inflow During Construction Of Cretaceous Shaft In Wuju Coal Mine

Coal mine water hazard is one of the five major disasters in mine construction and production,which are parallel with gas,fire,dust and dynamic geological hazards.It has brought great threat to coal mine safety production.In Wuju Coal Mine,the thickness of main shaft,auxiliary shaft and air shaf-t passing through the first section of Lower C retaceous Liupanshan Group(K1L1)is 267m,242m and 244m,respectively.During the process of shaft construction,technical problems such as large thickness of Lower Cretaceous aquifer,strong water-rich,large burial depth and difficult treatment have arisen.In this area,the non-freezing method has not successfully passed the aquifer with such large water inflow.Case.Through a series of hydrogeology and water inflow prediction analysis,this paper simulates and studies the change law of water pressure head,seepage velocity field and water inflow under different working conditions;compares and chooses control methods,puts forward the control scheme of wellbore water hazard of "working face pre-grouting + sectional excavation + back-wall grouting",and studies and designs the key construction technology,and solves the mine construction through implementation.The difficult problem is to pass through the strong aquifer safely and smoothly.The main work and achievements of this study are as follows:(1)The overall situation of main shaft,auxiliary shaft and return air shaft passing through the stratum in Wuju Coal Mine is summarized through data collection system.The structure,thickness and hydrogeological characteristics of three wellbore passing through the Cretaceous strong aquifer stratum are mainly studied.(2)According to the data of wellbore inspection holes,the data of wellbore water inflow under the condition of one-stage excavation are obtained by theoretical analysis and analogy method.There are great differences between the actual situation and the prediction of the Cretaceous water inflow in this area.The response of water pressure head,seepage velocity field and the change of water inflow are simulated by numerical calculation method under different conditions of wellbore.The variation of hydraulic head,seepage velocity field and water inflow in Cretaceous fractured aquifer during shaft excavation in this area are found,and the variation of water inflow under different excavation conditions with and without support is also found.(3)According to the study on the characteristics of Cretaceous water hazards and the law of water inflow in three wellbores of Wuju Coal Mine,a water hazard control scheme for vertical shaft construction is designed,which is "pre-grouting in working face + sectional excavation + post-wall grouting',.After the implementation,the water inflow is controlled safely and smoothly through the lower Cretaceous aquifer,and within the requirements of the national standards,so as to achieve safety and accident-free,the quality of wellbore construction is qualified,and the prevention and control The additional investment of water is only 28%of the freezing method,and the additional construction period is 50%of the freezing method.A safe and reliable technical way has been explored to control the water hazards in the Cretaceous fractured rock mass aquifer by grouting technology.In this paper,through the in-depth study of Cretaceous fractured rock aquifer in Wuju Coal Mine,the method of "working face pre-grouting + sectional excavation + post-wall grouting"in vertical shaft construction is put forward,and through successful implementation,the expected ideal effect is achieved,and the research goal is achieved.It has a very great reference value and promotion for the new mine in Longdong area and the shaft construction in the same type of strata in China.Significance of application.