The main mining project of deep mining in Tongshankou Copper Mine, including the neck section, the normal section of the wellbore, the bad rock section and the Matoumen of the -160m, -280m, -400m, -440m middle section, the -480m belt horsehead, the bucket measurement Drainage room, -540m powder mine recycling Ma Taumen and other excavation works.
The net diameter of the wellbore is 4.5m, the elevation of the wellhead is +59.2m, the elevation of the well bottom is -539.32m, and the neck section of the wellbore is 58m high. In the previous hydrogeological survey, the maximum water inflow in the main well was 1950m3/d and 81m3/h. The karst water is mainly located between -158 and -215m in the wellbore, and the aquifer is about 57m high. Due to the large water content and poor construction conditions, the construction of the wellbore is the key to the progress of the project and the main monitoring point for safe work. Therefore, it is necessary to adopt practical methods in the construction of the wellbore to quickly pass through the water under the premise of ensuring quality and safety. Floor. According to the position of the aquifer in the wellbore, the size of the water content, and the difficulty of construction, after comprehensive analysis, it is decided to use the pre-grouting of the wellbore working face to control the water inrush, and create conditions for the implementation of the “dry wellâ€.
1 grouting design
1.1 Grouting position and grouting form According to the hydrographic data of the wellbore, pay attention to the observation of hydrological changes during the construction of the wellbore. When approaching the aquifer, the construction should be advanced to the water drilling hole, the depth of the exploration hole is ≥10m, when the wellbore water inflow is expected When the ground level reaches 10m3/h, the wellbore is stopped and the working surface is pre-grouted, that is, the grouting drilling is started from -153m (the specific position is adjusted according to the actual construction conditions), and the drilling depth is 60m. The construction method is adopted in which the orifice is closed, the inside of the hole is circulated, and the grouting is performed from top to bottom.
1.2 Grouting Drilling Arrangement Grouting drilling is centered on the center of the wellbore and evenly distributed around the wellbore. The number of holes is calculated as follows:
Where, M is the number of grouting holes; C is the radius of the wellbore, 2.6 m; B is the distance from the center of the grouting borehole to the outer contour of the wellbore, 1.5 m; b is the spacing of the grouting holes, 3 m.
It is estimated that six grouting holes can be arranged to meet the requirements of wellbore construction.
1.3 Grouting material and slurry injection amount According to the hydrogeological data, in order to reduce the construction cost and speed up the construction progress, the grouting material is selected from cement-water glass slurry, and at the same time, to adjust the initial setting and final setting time of the slurry, a certain proportion of lime is added. As a condensing material, cement, water glass and quicklime are used as grouting materials.
Grouting cement is P. O32.5 grade ordinary Portland cement, the fineness of the cement is required to pass through the 80μm square hole sieve and the remaining amount is not more than 5%. The cement used must be fresh and free of agglomeration, and the unqualified cement is strictly prohibited. If necessary, water glass admixture or cement tail mortar-water glass double-liquid grouting may be used. The water glass has a modulus of 2.4 to 3.0 and a concentration of 30 to 45 waves. Lime is selected from local lime plants for lime production or industrial calcium hydroxide.
According to the drilling arrangement, the minimum effective influence radius of grouting is calculated to be 5.5m, and the grouting amount is estimated by the following formula:
Where, Q is the single hole grouting amount, m3; λ is the slurry loss coefficient, about 1; R is the slurry diffusion radius, 5.5 m; H is the slurry injection height, 60 m; N is the rock void ratio, 3%; γ is the rate of the slurry stone, which is about 1. It is calculated that the injection slurry per hole is about 171 m3, and the total grouting amount of the six holes is about 1026 m3. A total of 913 tons of cement and about 0.48 tons of water glass are required. The material consumption is subject to the actual consumption record on the construction site.
1.4 Concrete stop pad When the wellbore is in the process of excavation, when the water inflow from the wellbore reaches 10m3/h or more, stop the excavation and construction, clean the bottom rock, and carry out concrete stop pad construction. The pad is made of C35 concrete and the thickness is calculated as follows:
In the formula, Bn is the thickness of the pad, m; K is the safety factor, taking 3; PO is the final pressure of grouting, 15MPa; RO is 3m of the radius of the wellbore; R3-7 is the ultimate compressive strength of concrete 3-7d, Take 33.3MPa.
Calculated as Bn = 1.57m.
1.5 hole pipe buried hole pipe is made of Ф108×5 seamless steel pipe, length 3.0m, welded flange at the upper part of the hole to facilitate the connection of high pressure grouting valve. The lower depth of the hole pipe must pass through the concrete. The pad enters the complete bedrock and is plugged with cement slurry to ensure stability and reliability.
2 grouting construction
2.1 Grouting hole construction The grouting hole is constructed with MZ120-II type down-the-hole drilling rig , and the diameter of the drill bit is Ф90mm. The rig must be installed in a stable and secure manner.
According to the design of 6 grouting boreholes, the first, third and fifth drill holes will be constructed first, followed by the second, fourth and sixth drill holes. Borehole The hole depth, with hard rock change alloy or a diamond drill. Stick to the slope and ensure that the slope is less than 1%. In order to obtain the water permeability data of the bored rock, all the boreholes need to be subjected to the water pressure test from the top to the bottom. The length of the pressurized water test section is tentatively set at 30 m, which can be appropriately adjusted according to the actual drilling conditions. The pressure water test was carried out with flow rates of 10 m3/h, 20 m3/h, and 30 m3/h, and the stabilization time was greater than 30 min. At the same time, record the rock formation and hydrological changes.
2.2 Grouting operation In order to ensure the quality and effect of grouting, the slurry preparation and grouting must use automatic monitoring system to automatically record key parameters such as grouting pressure, slurry volume, slurry density and concentration. The materials used in the slurry shall be based on the materials available at the construction site. The selection, proportion and concentration of the slurry materials shall be determined after the test according to the geological conditions. The 3SNS200/10 grouting pump is used to grout the concentrated pulping station, and the mixed slurry is sent to each grouting hole through the pipeline for grouting. Before the grouting hole is applied to the design depth, the hole must be flushed before the grouting is to remove the residual rock powder in the borehole and the clay impurities filled in the rock fissure. Then, a pressure test is performed, and the slurry ratio is determined by the test, and the initial grouting concentration is selected. Grouting should be carried out by using the principle of first thickening and then thickening the slurry to increase the concentration of the slurry. If the injection slurry reaches about 5.0 m3 during grouting and the pressure is not too high or the pressure is very small, the slurry concentration can be increased. If the concentration of the slurry increases, the pressure rises sharply, or the amount of slurry is reduced, the slurry concentration should be reduced in time.
2.3 Grouting pressure adjustment Grouting pressure is 1.5 to 2.0 times of hydrostatic pressure. The initial grouting pressure should be flexibly controlled in the grouting process according to the consumption of the slurry and whether there is any slurry or slurry. During the grouting process, necessary measures should be taken to ensure that the slurry in the hole is unblocked. When the pressure at the wellhead is too large, measures should be taken to recover the slurry. According to the pressure, the amount of grouting should be controlled in time until the final pressure is reached, and it is stable for more than 30 minutes. .
2.4 End grouting When the grouting is evenly increased, the pressure is evenly increased to reach the design final pressure. At the same time, when the drilling suction amount is less than 10L/min, it is stable for 20~30min, and the grouting can be stopped. In order to save construction costs, the grouting hole also serves as a pumping inspection hole. After the grouting of each hole is completed, the hole-sweeping operation is performed in the No. 1 hole and the No. 3 hole, respectively, and the change of the water quantity in the hole during the hole-sweeping process is observed at any time. When there is obvious water in the hole, it should be re-grouted in the hole until the hole is flushed to the designed grouting depth without watering.
After the last section of the grouting hole reaches the grouting end standard, the hole is sealed by the "full hole grouting sealing method". The sealing pressure uses the maximum grouting pressure, and the sealing grouting duration is not less than 30 min.
3 Conclusion
Through the pre-grouting construction of the main working face of the deep mining of Tongshankou Copper Mine, the water inflow of the main wellbore working surface is controlled at about 3m3/h, which achieves good results, and the main wellbore can be constructed normally. Created conditions for the completion of the project on schedule. Practice has proved that in the construction of wells and lanes, when encountering rock formations with large water inflow, the pre-pre-grouting of the working face is a safe and reliable construction measure for smooth passage of the aquifer, which can improve the construction environment of the wellbore and ensure the safety and quality of the construction. Construction creates favorable conditions.
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Article source: Mining Technology; 2017.12(1)
Author: Xiong Hui wood; Daye Nonferrous Metals Co., Ltd. Tonglushan copper iron ore, Hubei Daye City, 435,101; Hubei Province, non-ferrous metal resources development and utilization Engineering Research Center, Hubei Huangshi 435000
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