Application of Shallow Hole Grouting and Water Blocking Technology in Baixiangshan Iron Mine

       1 Project Overview

Baixiangshan DangTuXian iron mine in Anhui Province, complicated hydrogeological conditions of the deposit, a lower Huangmaqing variegated strong aqueous rich sand fine powder, the maximum capacity of the unit gushing 8.204L / s · m, the maximum permeability coefficient 10.89m/d, which is the main water-filled rock layer of the mine. The aquifer is the indirect roof of the ore body, and the medium-rich water-bearing ore layer is a unified groundwater body in the natural state. There are mainly F1～F1111 faults in the area, among which 4 faults such as F2 are the water-rich faults mainly affecting infrastructure mining. Since the mine started construction in 2005, there have been three major water inrush accidents, from the previous infrastructure construction process. In the case of medium effluent, the maximum amount of water inflow from the pit exceeds 40,000 m3/d. In order to ensure the safety of the mining work, the principle of “doubt must be explored and every excavation will be explored” will always be adhered to during the construction process. The exploration of water exploration ensures that there is basically no large water inrush in the mine, but small crack water often occurs during the excavation process. The general grouting method has the disadvantages of long time and high cost.
2 effluent treatment analysis
       The design direction of the 164m roadway between the M3 and M12 along the west line of the Baixiangshan Iron Mine is 30° west to the west, and the floor of the roadway is 3‰ uphill.
       The net section of the lane is 5m wide, the wall height is 2.333m, and the arch height is 1.667m. The rock strata are metamorphic belts of diorite and horn-bearing irony silty siltstone and fine sandstone intercalated siltstone. Diorite mainly of albite, of kaolin, chlorite, and carbonates of phlogopite. The porphyry rock formations are dark red iron-bearing argillaceous siltstone, fine sandstone and silty mudstone. After metamorphism, the calcareous and muddy spots in the original rock are replaced by quartz , carbonate, albite, and specular iron to form spherical tuberculosis and bedding lens. Due to the influence of the anticline structure, the fractures of the rock formation are relatively developed, especially in the horn rock and the contact surface of the horn and diorite. The fracture is more developed and is the water conduit. When the roadway is driven to the section, the amount of water in the working surface is 8~35m3/h.
       Generally speaking, the working face of the roadway development project has water or scattered water. When the surrounding rock is better, the first method is to firstly construct a 1.5m thick anti-slurry wall to seal the rock face, and then embed several orifice pipes and solid pipes. After the pressure test, the full-section drilling curtain grouting begins. Or use a small duct full-section curtain grouting. These two methods have large material consumption, high cost and long construction period, and also affect the construction progress of the roadway. In order to reduce costs and speed up the construction of the project, Baixiangshan Iron Mine decided to use the shallow hole grouting and water shutoff technology in the roadway development and roadway mining.
       3 construction process
       (1) Arrangement and construction of grouting holes. The orifice tube is made of ordinary seamless steel tube with C=32mm pipe diameter; the 7655 type pneumatic rock drill for hole making is equipped with hollow hexagonal steel brazing, "one" type alloy drill bit, aperture C=42mm, drilling angle is opposite The outlet point, the hole depth is 4.5m; the pre-buried orifice tube size is C32mm×300mm×6mm (see Figure 1), one end is welded tightly with 60mm×60mm×4mm steel plate, and the other end is processed into fish scale buckle, 200mm from the top. Weld a connecting pipe with a diameter of 200mm and a threaded fastener to install a high-pressure ball valve, see Figure 2; wrap the hemp wire, and use a sledgehammer to pry the grouting hole into the hole tube, the external leakage is not more than 300mm, so as to facilitate installation Ball valve; when the pressure test reaches 7-8 MPa, the three-way grouting is connected to the ball valve, and grouting can be started. The orifice tube is simple in processing, simple in operation, low in cost, convenient, fast, efficient and safe.

       (2) Preparation for grouting construction. Select a suitable section in the roadway as a pulping work point, and set up a mixer, a slurry tank, a water bucket and a grout pump. Before the grouting construction, prepare the wind, water, electricity and other pipeline systems as well as various grouting equipment and grouting materials, and carry out maintenance and repair to ensure the integrity, take anti-running and leakage treatment measures on the roadway surface.
       (3) Grouting construction. Grouting equipment Material tool storage → pulping → pipeline connection → water injection → grouting → stop grouting to close the grouting valve.
       (4) Grouting parameters. Grouting pressure is to push the slurry to overcome various flow resistance, so that the slurry diffuses in the bedrock fissure. It is recommended to use 2~2.5 times of hydrostatic pressure. During the grouting process, the crack is gradually filled due to the filling of the slurry, and the flow rate is It decreases with the increase of grouting pressure. The flow rate in the bedrock fissure is 50~60L/min. The injection amount is closely related to the grouting pressure. It is necessary to have a reasonable grouting pressure to ensure the grout injection volume. It can be determined by the amount of grouting water and the amount of flushing fluid leakage; under the same conditions, the thicker the slurry, the greater the viscosity and the smaller the diffusion distance. The bedrock fissure water should generally be concentrated slurry, and the concentration of the slurry should be increased after continuous injection of each concentration level for 40-50 minutes.

(5) Grouting process. Connect the grouting pipeline according to the grouting requirements, adjust the grouting pump safety valve, and then open the pump grouting after the test operation is normal; put an appropriate amount of water in the mixing tank, and then put the cement into the ratio according to the ratio to make the water of the slurry The ash ratio is controlled in the range of 0.7 to 0.8. The slurry is stirred by a pneumatic stirrer. The stirring time has a very important effect on the thorough mixing of the slurry and water. The stirring time is too short, and the slurry and water are not uniformly mixed, which greatly affects the fluidity of the slurry. 5 min; pump grouting, stop grouting when the grouting pressure reaches the design final pressure. The order of grouting is performed in order from the inside to the outside. During the grouting process, the changes of grouting parameters such as grouting pressure and grouting amount are observed and recorded at any time. In addition, observe the leakage phenomenon on the surface of the roadway at any time. In case of running slurry leakage, measures should be taken in time to block the paste. When a large amount of slurry is leaked, a proper amount of water glass can be added to the cement slurry for grouting, and then replaced with cement after plugging. Single slurry. The grouting of each hole shall be continuously injected. If it is necessary to suspend the grouting, a certain amount of clean water shall be injected into the hole to keep the grouting passage smooth. During the grouting process, it is necessary to observe the pressure rise of the pressure gauge. It is necessary to set up a special person to observe whether there are abnormal conditions in the lane top, the roof top and the orifice tube, and the problems should be dealt with in time. During the grouting, the construction personnel should pay attention to the running condition of the grouting pump and the slurry discharge to ensure the integrity of the grouting pump.
       4 grouting effect
       The Baixiangshan Iron Mine wind well--Mm to M12 in the middle of the 390m middle section has a total of 164m roadway fissure water, scattered water and fault water output of 8 ~ 35m3 / h, an average of 20m3 / h per 5m. After the shallow hole grouting of the orifice pipe is used to grout the water in the section, the slurry in the fracture zone can be observed to be filled with the slurry very densely. The measured water inflow is 0.3-0.4 m3/h. The plugging rate has reached over 97%, and the tunneling has increased by 120% compared with the previous one. It has achieved the intended purpose, and the tunnel construction has successfully passed through the aquifer.
        references:
       [1] Jiang Yusong. Determining and burying the length of the grouting orifice pipe in the working face of the roadway [J]. Mining Research and Development. 2006, 26 (3).
       [2] Li Fanghui. Application of small conduit grouting technology in tunnel engineering [J]. Shanxi Architecture, 2007 (7).
       [3] Wang Yongyi, Song Chengbiao. Application and discussion of shallow hole pre-grouting technology in working face [J]. Coal Science and Technology, 2004 (04).
       [4] Deng Renqing. High-pressure water-rich tunnel grouting and water blocking construction technology and application [J]. Journal of Underground Space and Engineering, 2006 (03).