Finite Element Analysis of Rock Damage Hollow Outside Shaft Wall Lining and Grouting

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Finite Element Analysis of Rock Damage Hollow Outside Shaft Wall Lining and Grouting ZHANG Xiangdong, YIN Xiaowen,Zhang Shukun Institute of Civil Engineering and Transportation, Liaoning Technical University,
Finite Element Analysis of Rock Damage Hollow Outside Shaft Wall Lining and Grouting ZHANG Xiangdong, YIN Xiaowen,Zhang Shukun Institute of Civil Engineering and Transportation, Liaoning Technical University, Fuxin China 123 Abstract: Crushing sand and vertical cavity wall have been threatening the safety of coal mine in production, the analysis about destroyed vertical stability and processing method are concerned. This paper used the FEM software ADINA, with the combination of Mohr - Coulomb criterion and tensile failure criteria,and simulate the damage of the wall cavity and grouting according to the inspection at original space, the basic rules among them had been studied. According to the result of analysis, grouting scheme was formulated. The analysis about numerical simulation shown that: crushing sand and vertical cavity wall would have an adverse effect on the stability of shaft body and it could cause the land subsidence; Grouting pressure has a direct impact on the stability of shaft body. When grouting pressure was large enough, the vertical stress could appear shaftlining pull pressure; It could lead to wall the rupture of the wall. Keywords:vertical, finite element analysis, wall damage, grouting reinforcement Foreword The research about methods of preventing and managing damaged shaft body includes designing the shaft body, execution of works and the damage of RC materials and so on, and we need to consider combining the damage of the shaft body with the foregoing issues [1]. At present,main methods are taking the new design of vertical shaft before building well or having rainfall measures for the surrounding soils [2]. If shaft wall of the vertical is damaged, we should damage the wall and have the wall grouting, it can stop rapidly from the water of the broken wall, and can play a certain role of reinforcing wall for the rock of the local scope and the rupture of the wall of the well, but it can not prevent the vertical deformation of vertical shaft effectively, and can not reinforce aquifer and weathered zone around the bottom ;The curtain grouting has influenced the rupture of the wall, but it also has some disadvantages, it is difficult to control the implementation process and costs too much, and can not be cured completely [3-4]. Strengthen of shaft wall can only repair them temporarily, within a short time, and shaft wall will be destroyed again because of destruction of water on the bottom wall [5-9]. Discharging pressure tank can control deformation and fracture of vertical shaft betterin a long time, but it need to spend to much time. So it affects the normal work of production [6-1]. Sometimes we need to combine all the Fund project: Education Department of Liaoning Province Key Laboratory of Science and Technology Project(28S114),National Natural Science Foundation ( ), Liaoning Provincial Higher talents to support project(28rc23) methods. 1 Engineering Survey Rong-hua Vertical Shaft lies in Heilongjiang province, it has three shaft bodies, main shaft, auxiliary shaft and the wind shaft. The diameter of main shaft is 6.5 m, its depth is 921 m. The borehole of ~ 19m will use reinforced concrete for the thickness of 85mm. 3# reinforced concrete for 6mm thick will be used below 19m. The diameter of auxiliary shaft is 8. m, it s 866m deep. The borehole of ~ 155m will use reinforced concrete for the thickness of 85mm. 3# reinforced concrete for 6mm thickness will be used below155m. Shaft bodies of main shaft and auxiliary shaft appear different degrees crushing sand and coal slide when we use the fourth sand layer, new three-line silty sandstone, the new three-line diatom rocks, new three-line basalt, and the old three-line sandstone and so on, and form some cavity, and it s the largest in poor cementation between basalt and the old three-line sandstone. The existence of hollow of main shaft and auxiliary shaft will affect the safety of shaft wall seriously, it may cause borehole wall damaged by sudden, cause accidents, and can also cause the subsidence of the ground. It can t make ground ascension equipment run. 2 Main Engineering Geological Conditions and the Reasons for Producing Cavity 2.1 Main Engineering Geological Conditions Aquifer around the mine field can be divided into eight aquifers according to the geological era, lithology, burial condition (1) quaternary alluviation, diluvial pore aquifer SciRes. 82 (Ⅰ); (2) tertiary top porosity and fracture aquifer (Ⅱ) ; (3) tertiary upper fracture and porosity aquifer (Ⅱ2); (4) the tertiary central fracture and porosity aquifer (Ⅱ3) ;(5) the tertiary fracture and porosity aquifers on the bottom (Ⅱ4); (6) Jurassic son erosional and fissure aquifer (Ⅲ1) ; (7) Jurassic son layer air-slake and fracture aquifer (Ⅲ2) (8) Jurassic son fault basin (Ⅲ3). Aquiclude around the field lies between the quaternary top deposit and tertiary strata for clay, clay shale and basalt. Here are points as follows: (1) Quaternary water-resisting clay water-resisting layer (G);(2) Tertiary upper thick mudstone water-resisting layer (G1);(3) Tertiary middle basalt water-resisting layer (G2); (4) Tertiary middle-lower mudstone water-resisting layer (G3, G4). sition of main and auxiliary shafts, the distance b etween them is about 71m, diameter borehole of main shaft is 6.5 m. Diameter borehole of the au xiliary shafts is 8m, vertical is 35m deep, it s 1 m toward around two wellbores. The main purp ose of the model calculation that is buried 28m deep in borehole is to study the effect of the hol e to fall across the surface of the shaft and the s ettlement. According to the needs of the model, n etwork density in different areas is different. A 3 d simulation rendering is shown in Figure 1: 2.2 The Reasons for Producing Holes According to the strata structure of the main shaft an d the auxiliary shaft,we know there are multilayer s andstone layers and water basalt weathered zone for mation in tertiary and quaternary stratums.when we dig wells to the aquifer, without additional grouti ng or frozing, water in the aquifer gets into the well bore and gushing water is can cause coal sli de easily. In the 199s Chinese special construction method (freezing method and drilling method) can no t still reach the depth of the mineshaft, so digging w ells in common ways can make the ability of crushin g sand flood insufficient during the construction. In a ddition, we don t realize the harm that the tertiary u niaqenetic dsandstone and basalt cause well. So we d on t use grunting reinforcement and sealing main aqu ifer, flowing sand layer, weathering fracture zone; An other reason is that tertiary strata is buried deep, it h as large rock stress, low intensity (diatom rock).pa rts of sandstone has not been fully consolidated d iagenetic yet, it s easy to collapse and flow. Ther e are some multilayer confined aquifers in the Str ata. During the process of water to wellhole, it carries over sand layer. Therefore, in the process of excavation and supporting it will appear large amounts of water and sand dyke. 3 Numerical Simulation of the Damaged Shaftlining 3.1 Calculation Model and Boundary Conditions In this paper we used software ADINA to analy ze shaftlining destruction, it is a general analysis software. Model is made by the relationship in po Figure 1 Three-dimensional finite element model grid figure According to the model, level constraint was exerted on each boundary of the model, even if horizontal displacement of the model is zero, the bottom border was fixed. We can also say, boundary horizontal displacement on the bottom and vertical displacement are zero, the top of the model was free boundary. Loading produced by gravity was exerted in the vertical direction, the lateral stress is produced by gravity. In the calculation we used the mohr-coulomb model, in which the elastic-plastic constitutive model, surface of the material obeys the mohr-coulomb buckling failure criterion (shear yields function) and tensile yield criterion. Shear stress in the face of buckling is ascertained by two kinds of failure criterions. 3.2 Selection of Calculation Parameter According to the survey report and engineering experience and the characteristic parameter selection of wall, we ll show Table 1. According to the engineering material, there are the main cavities of excavation from 285m to 28m It s convenient to change the irregular area into a regular cubes of 75m SciRes. position character Table 1 density ( kg/m 3 ) Parameters of calculating model physical mechanics bodiness modulus(gpa) tensile strength(mpa) cohesive (MPa) Internal friction horn( ) ~65m grit mudstone m~15m diatom m~28m basalt m~353m mudstone sandstone wellbore concrete The Analysis of Simulated Result Finite element simulation results are shown in Figure2, Figure3, Figure4, Figure5. Figure.2 Isogram of the surface subsidence(m) 下沉值 (m) 距离 ( m) 地表下沉曲线 15m 处岩层下沉曲线 Figure.4 Graph of the surface subsidence and rock diagram Figure.3 Isoline for cross-section 15m from the surface subsidence(m) (1) From Figure 2, Figure 3 subsidence displacement was like a concave pocket, two wellbore subsidence in the middle was bigger than on both sides, it assumed symmetrical distribution. From the surface subsidence curve we could see damage degree of scope and maximum sinking value between main and subsidiary shafts was about.15m,the farther,the smaller sedimentation value would be. From figure 3 you could see the deeper from the surface, the closer to the surface subsidence, the bigger sedimentation value will be. (2) From Figure 4 vertical shaft sinking increased with depth increases. In the present situation maximal displacement of surface was about 13.5 cm. It was just a larger hole wellbore area of surface subsidence under the influence, different sizes from other areas layers empty of and of cavitation of surface subsidence of fracture, might be greater than the current subsidence. It would have worse influence in the future. You could see its basic oval from the surface displacement distribution, thus sinking mapped surface subsidence was a symmetric distribution curve. (3) From Figure 5, under the influence of cavern form local stress. This kind of rock mass would be weakened under the action of groundwater, which further collapse and the cavitation. Figure.5 Two wellbore maximum shear stress 4 The Numerical Simulation and G-Routing Constructions Scheme 4.1 Grouting Scheme The selecting of treatment methods is the same parameter calculation basically. Now we have an example of main shaft to design grouting, parameter in the auxiliary will be shown in conclusion. According to different situations, we ll adopt different grout filling reinforcing scheme, specific as follows: (1) According to construction conditions of the main shaft and geological conditions of the regional,we will divide into five different groutings, grouting engineering requirements different grouting materials. (2) Groute wall rock the main shaft in the next 5 ~ 8m grouting area, reinforcing formation check the sealing reinforcement grouting not down. (3) Have cement single grouting strengthening strata in the area that only occurs the bass drum and has SciRes. 84 no disturbance. (4) Collapse of serious and produce empty areas, we should grout cement and coal ash to fill, because of filling lots of coal ash can reduce the cost of grouting materials. In addition, according to quantity of the grouting and water gushing conditions, we should infuse water liquid cement, double block to strengthen formation water, reduce wellbore yield. 4.2 Asgrouting Pressure Table 2 Design in 8m, 5m, 2m, wall was added in 1MPa asgrouting pressure 3MPa, 5MPa, 7MPa 1MPa, and calculate, which examines the stress changes in the wall, we have 15simulation schemes, as shown in table 2. In order to intuitive see the sidewall stress clearly, from the buried depth from 255m to 35m, take shaft wall 5m long, we need to half of a length of to calculate. After 3 lengths of grouting depth, the 5 kinds of grouting injection, pressure 15 schemes, the calculation results from the level of stress contours analysis conclusion: The grouting scheme of Different distance from wall under different pressure distance sidewall 2 meters asgrouting pressure (MPa) plan1 plan2 plan3 plan4 plan5 5 meters plan6 plan7 plan8 plan9 plan1 8 meters (1) Distance of the sidewall, the bigger the grouting pressure is, the bigger sidewall stress on the maximum level will be, it s dad for sidewall stability. (2) Under the same pressure, the farther away from shaft lining by horizontal stress, the smaller of sidewall stability, the better. (3) In the same sidewall distance, the greater grouting pressure it is, the maximum compressive stress of vertical shaft is smaller, more than 7MPa sidewall grouting pressure when stress is tensile stress. Sidewall tensile strength, low tensile stress appears in the construction of the wall to some place craze. Appropriate asgrouting pressure should be less than 5MPa. 井壁压力 (MPa) 注浆压力 (MPa) plan11 plan12 plan13 plan14 plan15 距井壁 2m 距井壁 5m 距井壁 8m Figure.6 Maximum horizontal wellbore compressive stress table (MPa) 垂直应力 (MPa) 距井壁 8m 距井壁 5m 距井壁 2m 注浆压力 (MPa) Fig.7 Maximum vertical shaftlining table (MPa) 5 Conclusions Vertical shaft from the engineering geological mechanics is a dynamic process; the environment of shaft wall is a nonlinear dynamic system of wellbore. It is the influence of geological environment, and interaction of geological environment and mining activities and interactions of soil and the wall of a well[11]. We got the following conclusions after considering the factors and numerical simulation results: (1) The subsidence and the distance from the depth of the shaft, have positive correlation. General surface subsidence is symmetrical distribution, (2) Asgrouting pressure has a direct impact on the stability of shaft. When asgrouting pressure reaches a certain value, the vertical stress can appear wall stress, level pressure are broken wall. (3) To ensure the safety and wellbore during the grouting and the normal operation of the borehole wall after, production, we should have long-term monitoring. References [1] Bi Siwen. XuHuai Area Coal Mine Shaft Deformation and Failure Mechanism of Countermeasures [J] Well Construction Technology, 1996,17(3):26~29(in Chinese) ) [2] Yun Long Concise Construction Engineering Manuals [M]. Beijing: Coal Industry Press 23 (in Chinese) [3] Ge Xiaoguang The Ground and Wall Fracture Grouting Treatment Engineering Analysis of Disasters[J] Mining Design and Construction, 24,6:41~44(in Chinese) [4] Wu Huaijun Study on Failure Stress of Shaft Wall [J] China's Safety Science Journal (in Chinese) [5] Song Wenxin,Zhao Xiaopei. On the Prevention and Treatment of Damages in the Wall of Shaft Sunk by Freezing Method [J] China's Coal, 26,26(6):34~4(in Chinese) SciRes. 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Jing Accepted the Cause of Damage and Control Method [J] Soil Mechanics 24,12 (25):1977~198 (in Chinese) [8] Yao Zhishut,Yang Junjie,Sun Wenru-o.Experimental Study on Sliding Shaft Lini-ng Mechanical Mechanisms Under Ground S-u bsidence Conditions [J] Journal of Coal Sci-ence and Engineerin g.23t 9(1):95~99 [9] BruneauG,TyletDB,Hadjigeorgiou J.Influence Offaultingon a Mine Shafl a Ca-se Study:Part l-background and Instrumentation [J].International Journal of Reck Mechanics and Mining Science- 23 4(11:95~111) [1] Rejeb A,Bruel D.Hydromechanical Effects of Shaft:Sinking at the Sella Fields Site [J].Intemational Journal of Rock Mechanics and Mining Science-21.38(1):17~29 [11] Li Wenping Deep in the Shaft Fracture Surface Engineering Geological Research [M] China University of Mining, Press. 2 (in Chinese) SciRes. 86
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