斜沟煤矿5.0 Mta新井设计含5张CAD图
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设计任务书学院 专业年级 学生姓名 任务下达日期:20XX年1月8日毕业设计日期:20XX年3月12日 至 20XX年6月8日毕业设计题目: 斜沟煤矿5.0 Mt/a新井设计毕业设计专题题目: 煤与瓦斯突出预防及控制技术毕业设计主要内容和要求:以分散实习矿井斜沟煤矿条件为基础,完成斜沟煤矿5.0Mt/a新井设计。主要内容包括:矿井概况、矿井工作制度及设计生产能力、井田开拓、首采区设计、采煤方法、矿井通风系统、矿井运输提升等。结合煤矿生产前沿及矿井设计情况,撰写一篇关于煤与瓦斯突出预防及控制技术的专题论文。 完成2011年中国煤炭科技杂志上与采矿有关的科技论文翻译一篇,题目为“Effect of grout properties on the pull-out load capacity of fully grouted rock bolt”,论文7520字符。院长签字: 指导教师签字:Effect of grout properties on the pull-out load capacity of fully grouted rock boltA. Klc, E. Yasar*, A.G. CelikAbstractThis paper represents the result of a project conducted with developing a safe, practical and economical support system for engineering workings. In rock engineering, untensioned, fully cement-grouted rock bolts have been used for many years. However, there is only limited information about the action and the pull-out load capacity of rock bolts, and the relationship between boltgrout or groutrock and the influence of the grout properties on the pull-out load capacity of a rock bolt. The effect of grout properties on the ultimate bolt load capacity in a pull-out test has been investigated in order to evaluate the support effect of rock bolts. Approximately 80 laboratory rock bolt pull-out tests in basalt blocks have been carried out in order to explain and develop the relations between the grouting materials and untensioned, fully grouted rock bolts. The effects of the mechanical properties of grouting materials on the pull-out load capacity of a fully grouted bolt have been qualified and a number of empirical formulae have been developed for the calculating of the pull-out load capacity of the fully cement-grouted bolts on the basis of the shear strength, the uniaxial compressive strength of the grouting material, the bolt length, the bolt diameter, the bonding area and the curing time of the grouting material.Keywords: Rock bolt; Grouting materials; Bolt pull-out load capacity; Bolt geometry; Mortar1. IntroductionIn rock engineering, rock bolts have been used to stabilise openings for many years. The rock bolting system may improve the competence of disturbed rock masses by preventing joint movements, forcing the rock mass to support itself (Kaiser et al., 1992). The support effect of rock bolt has been discussed by many researchers(e.g. Hyett et al., 1992; Ito et al., 2001; Reichert et al., 1991 and Stillborg, 1984). Rock bolt binds together a laminated, discontinued, fractured and jointed rock mass. Rock bolting not only strengthens or stabilizes a jointed rock mass, but also has a marked effect on the rock mass stiffness (Chappell, 1989). Rock bolts perform their task by one or a combination of several mechanisms. Bolts often act to increase the stress and the frictional strength across joints, encouraging loose blocks or thinly stratified beds to bind together and act as a composite beam (Franklin and Dusseault, 1989). Rock bolts reinforce rock through a friction effect, through a suspension effect, or a combination of two. For this reason, rock bolt technique is acceptable for strengthening of mine roadway and tunnelling in all type of rock ( Panek and McCormick, 1973).Generally rock bolts can be used to increase the support of low forces due to the diameter and the strength of the bolt materials. They enable high anchoring velocity to be used at closer spacing between bolts.Their design provides either mechanical clamping or cement grouting against the rock (Aldorfand Exner,1986).Anchorage system of rock bolt is normally made of solid or tube formed steel installed untensioned or tensioned in the rock mass (Stillborg, 1986). Rock bolts can be divided into three main groups according to their anchorage systems (Franklin and Dusseault, 1989;Aldorfand Exner, 1986; Hoek and Wood, 1989; Cybulski and Mazzoni, 1989). First group is the mechanically anchored rock bolts that can be divided into two groups: slit and wedge type rock bolt, expansion shell anchor. They can be fixed in the anchoring part either by a wedge-shaped clamping part or by a threaded clamping part. Second group is the friction-anchored rock bolts that can be simply divided into two groups: split-set and swellex. Friction-anchored rock bolts stabilise the rock mass by friction of the outer covering of bolt against the drill hole side. The last group is the fully grouted rock bolts that can also be divided into two groups: cement-grouted rock bolts, resin grouted rock bolts.A grouted rock bolt (dowel) is a fully grouted rock bolt without mechanical anchor, usually consisting of a ribbed reinforcing bar, installed in a drill hole and bonded to the rock over its full length (Franklin and Dusseault, 1989). Special attention should be paid to cement-grouted bolts and bolts bonded (glued, resined) by synthetics resins for bolt adjustment. Grouted bolts fix the using of the coherence of the sealing cement with the bolt rod and the rock for fastening the bolts. Synthetic resin (resined bolt) and cement mortar (reinforced-concrete bolt) can be used for this type rock bolt. These bolts may be anchored in all type of rock. Anchoring rods may be manufactured of several materials such as ribbed steel rods, smooth steel bars, cable bolts and other special finish (Aldorfand Exner, 1986).Grouted bolts are widely used in mining for the stabilisation of tunnelling, mining roadway, drifts and shafts for the reinforcing of its peripheries. Simplicity of installation, versatility and relatively low cost of rebars are further benefits of grouted bolts is comparison to their alternative counterparts (Indraratna and Kaiser,1990).Bolts are self-tensioning when the rock starts to move and dilate. They should therefore be installed as soon as possible after excavation, before the rock has started to deform, and before it has lost its interlocking and shear strength.Although several grout types are available, in many applications where the rock has a measure of short term stability, simple Portland cement-grouted reinforcing dowels are sufficient. They can be installed by filling the drill hole with lean, quickly set mortar into which the bar is driven. The dowel is retained in up holes either by a cheap form of end anchor, or by packing the drill hole collar with cotton waste, steel wool, or wooden wedges (Franklin and Dusseault, 1989).Concrete grouted bolts use cement mortar as a bonding medium. In drill holes at minimum of15 8 below the horizontal plane, the mortar can simply poured in, whereas in raising drill holes various design of bolts or other equipment is used to prevent the pumped mortar from flowing out (Aldorfand Exner,1986).The load bearing capacity off ully cement-grouted rock bolts depends on the bolt shape, the bolt diameter, the bolt length, rock and grout strength. The bond strength off ully cement-grouted rock bolts is primarily frictional and depends on the shear strength at the boltgrout or groutrock interface. Thus any changes in this interfaces shear strength must affect the bolt bond strength and bolt load capacity.This laboratory testing program was executed to evaluate the shear strength effect on the bond strength of the boltgrout interface of a threaded bar and the laboratory test results confirm the theory.2. Previous solutionsThe effectiveness of a grouted bolt depends on its length relative to the extent of the zone of overstressed rock or yield zone. The shear and axial stress distributions of a grouted bolt are also related to the bolt length because equilibrium must be achieved between the bolt and the surrounding ground (Indraratna and Kaiser,1990).Bearing capacities of cement-grouted rock bolts (Pb) and their anchoring forces are a function of the cohesion of the bonding agent and surrounding rock, and the bolting bar. The ultimate bearing capacity of the bolt (Pm) is expressed as follows (Aldorf and Exner, 1986): (1)where kb, safety coefficient (usually kb =1.5); C1, cohesion of the bonding material on bolting bar, ld, anchored length of the bolt, ds, bolt diameter. (2)where dv, drill hole diameter;C2,cohesion of the bonding material with surrounding rock(carboniferousrocks and polyester resins C2 =3 MPa). (3)where C3, shearing strength of the bonding material.The maximum (ultimate) bearing capacity of the bolt (Pm ) will be the lowest value from P1to P111.Bearing capacities of all type bolts must also be evaluated from the view point of the tensile strength of the bolt material (Pms), which must not be lower than the ultimate bearing capacity resulting from the anchoring forces of bolts in drill holes (Pm). It holds that (4)where Pms, the ultimate bearing capacity of the bolt with respect of the tensile strength of the bolt material;Pm, the ultimate bearing capacity of the bolt.3. Laboratory study3.1. ExperimentsThe pull-out tests were conducted on rebars, grouted into basalt blocks with cement mortar in laboratory. The relations between bolt diameter (db) and pull-out load of bolt (Pb) (Fig. 2), bolt area (Ab) and pull-out load of bolt (Pb) (Fig. 3), bolt length (Lb) and pull-out load of bolt (Pb) (Fig. 5), water to cement ratio (w/c) and bolt bond strength (b) (Fig. 7), mechanical properties of grout material and bolt bond strength (b) (Fig. 9,Figs. 10 and 11), and curing time (days) and bolt strength (Figs. 12 and 13) were evaluated by simple pull-out test programme.The samples consisted of rebars (ranging 1018 mm diameters two by two) bonded into the basalt blocks. These basalt blocks used have a Youngs modulus of 27.6 GPa and a uniaxial compressive strength (UCSg) of 133 MPa. Drilling holes which were 10 mm larger than the bolt diameter, having a diameter of 20 28 mm for installation of bolts, were drilled up to 1532 cm in depth. The bolt was grouted with cement mortar. The grout was a mixture of Portland cement with a water to cement ratio of 0.34, 0.36, 0.38 and 0.40 cured for 28 days. In order to obtain different grout types that have different mechanical properties, siliceous sand and fly ash were added in a proportion of 10% of cement weight and white cement with a water to cement ratio of 0.40. The sand should be well graded, with a maximum grain size of v2 mm (Schack et al., 1979). The Youngs modulus of the grouts was measured during unconfined compression tests and shear strength was calculated by means of ring shear tests.The test set-up is illustrated schematically in Fig. 1 and the procedure is explained below:1. After filling prepared grout mortar into the hole, bolt is inserted to the centre of drilling hole.2. After curing time, the rebars in the rock were axially loaded and the load was gradually increased until the bolt failed.3. The bond strength (b) was then calculated by dividing the load (Pb) by surface area (Ab) of the bolt bar in contact with the grout. 4. Pull-out tests were repeated for various grout types, bolt dimensions and curing times.The influence of the bolt diameter and the bond area on the bond strength of a rock bolt can be formulated as follows (Littlejohn and Bruce, 1975): (5)where b, ultimate bolt bond strength (MPa); Pb, maximum pull-out load of bolt (kN); db, bolt diameter (mm); lb , bolt length (cm); dblb , bonded area (cm2).3.2. Analysis of laboratory test results3.2.1. Influence of the bolt materialBolt diameters of 10, 12, 14, 16 and 18 mm were used in pull-out tests. Typical results are represented in Table 1, Figs. 2 and 3. The most important observations were:(1)The maximum pull-out load (Pb) increases linearly with the section of the bolt while embedment length was constant.(2) Bolt section depends upon bolt diameter. The relation between bolt diameter and bolt bearing capacity can be explained as follow empiric formulae (Fig. 2). (6)(3) The values of bolt bond strength were calculated between 5.68 and 5.96 MPa (Table 1).Bolt lengths of 15.0, 24.7, 27.0, 30.0 and 32.0 cm were used in pull-out tests as seen in Fig. 4. Typical results are represented in Table 2, and Figs. 5 and 6.The most important observations were:(1) The pull-out force of a bolt increases linearly with the embedded length of the bolt. (7) (2) Maximum pull-out strength of a bolt is limited to the ultimate strength of the bolt shank.3.2.2. Influence of grouting materialThe water to cement ratio should be no greater than 0.40 by weight; too much water greatly reduces the long-term strength. Because, part of the mixing water is consumed by the hydration of cement used. Rest of the mixing water evaporates and then capillary porosities exist which results in unhomogenities internal structure of mortar. Thus, this structure reduces the long-term strength by irregular stress distribution (Neville, 1963;Atis, 1997). To obtain a plastic grout, bentonit clay can be added in a proportion of up to 2% of the cement weight. Other additives can accelerate the setting-time, improve the grout fluidity allowing injection at lower water to cement ratios, and make the grout expand and pressurize the drill hole. Additives, if used at all, should be used with caution and in the correct quantities to avoid harmful side effect such as weakening and corrosion (Franklin and Dusseault, 1989).The water to cement ratio (w/c) in grouting materials considerably affects pull-out strength of bolt. As seen in Table 3, UCSg and shear strength (tg) of grout in high w/c ratio show lower values whereas in low w/c ratio higher values. The ratio between 0.34 and 0.40 presents quite good results. Although the w/c ratio of 0.34 gives the best bond strength, groutibility (pumpability) decreases and a number of difficulties in application appear. In high w/c ratio, the pumpability of grouting materials into the drilling hole is easy but the bond strength of bolt decreases (Figs. 7 and 8).The bond strength off ully cement-grouted rock bolts is primarily frictional and depends on the shear strength at the boltgrout or groutrock interface. Thus any change in this shear strength of interfaces affects the bolt bond strength and load capacity. The influences of mechanical properties of grouting materials on the bearing capacity of bolt can be described as follows:(1) The uniaxial compressive and shear strength of the grouting materials has an important role on the behaviour of rock bolts. It was observed that increasing shear strength of the grouting material logarithmically increases bolt bond strength as shown in Table 4 and Fig. 9. The relation between grout shear strength and bolt bond strength was formulated as follows: (8) (2) Table 4 and Fig. 10 show that increasing grout compressive strength considerable increases the bond strength of the grouted bolts. (9) (3) In Fig. 11 and Table 4 show that there is another relationship between Youngs modulus of grout and bolt bond strength. Increasing the Youngs modulus increases bolt bond strength. (10) 3.2.3. Influence of the curing timeAn important problem in the application of cementgrouted bolts is the setting time of the mortar, which strongly affects the stabilizing ability of bolt. Cementgrouted dowels cannot be used for immediate support because of the time needed for the cement to set and harden (Franklin and Dusseault, 1989).In the pull-out tests, eight group ofbolts having same length and mortar with a water to cement ratio of0.4 were used for determining the effects of curing time on the bolt bond strength. Each group ofr ock bolt testing was performed after different setting times (Table 5). As can be seen in Figs. 12 and 13, the strength of bolt bond increases rapidly in 7 days due to curing time. However, the bond strength of bolt continues to increase rather slowly after 7 days.Rock bolts may lose their supporting ability because of yielding of bolt material, failure at the boltgrout or groutrock interface, and unravelling of rock between bolts. However, laboratory tests and field observations suggest that the most dominant failure mode is shear at the boltgrout interface (Hoek and Wood, 1989). So, this laboratory study focussed on the interface between rock bolt and rock and the mechanical properties of grouting materials.4. ConclusionsThe laboratory investigation showed that the bolt capacity depends basically on the mechanical properties of grouting materials which can be changed by water to cement ratio, mixing time, additives, and curing time. Increasing the bolt diameter and length increases the bolt bearing capacity. However, this increase is limited to the ultimate tensile strength of the bolt materials. Mechanical properties of grouting materials have an important role on the bolt bearing capacity. It is offered that the optimum water to cement ratio must be 0.340.4 and the mortar have to be well mixed before poured into drill hole. Improving the mechanical properties of the grouting material increases the bolt bearing capacity logarithmically. The best relationship was observed between grout shear strength and bolt bond strength. Increasing the curing time increases the bolt bond strength. Bolt bond strength of 19 kg/cm2 in first day,77 kg/cm2in 7 days and 86 kg/cm2in 35 days was determined respectively. The results show that bolt bond strength increases quickly in first 7 days and then the increase goes up slowly.Bond failure in the pull-out test occurred between the bolt and cement grout, of which the mechanical behaviour is observed by shear spring. This explains the development of bolt bond strength and the failure at the boltgrout interface considering that the bond strength is created as a result of shear strength between bolt and grout. This means that any change at the grout strength causes to the changing of bolt capacity. The failure mechanism in a pull-out test was studied in order to clarify the bond effect of rock bolt. Thus one main bond effect was explained from bond strength of rock bolts.中文翻译水泥浆性能对充分注浆锚杆拉拔承载力的影响A. Klc, E. Yasar*, A.G. Celik摘要:本文代表了一项在安全、实用、经济的支持系统指导下的工程结果。在岩石工程中,没有被拉紧的且被水泥充分注浆的锚杆已使用多年。然而,对锚杆的作用过程和其拉拔载荷的能力,以及锚杆注浆或注浆的关系,水泥性能对充分注浆锚杆拉拔承载力的影响研究却很少。为了评估锚杆支护效果,我们开始对水泥性能对最终锚杆在拉拔试验载荷能力的影响进行了研究。大约80个针对玄武岩块的锚杆拉拔试验实验室已开始进行研究以用来解释和发展注浆材料和松弛的充分注浆锚杆之间的联系。这种注浆材料的力学性能对一个完全锚杆拉拔承载力的力学性能的影响已被数量化,而且,为了计算充分注浆锚杆的承载能力,在考虑剪切强度,注浆材料的单轴抗压强度,锚杆长度,锚杆直径,粘结面积及注浆材料固化时间的基础上,一些经验公式已被提出和不断的发展。关键词:锚杆;注浆材料;锚杆拉拔承载能力;锚杆几何形状;砂浆1引言在岩土工程中,锚杆已多年被用来稳定开口。该锚杆支护系统可通过阻止接缝处移动,迫使岩块支持其本身来提高岩体抗扰动能力(Kaiser et al., 1992)。对这样的岩锚支护效果已被许多研究者讨论过(e.g. Hyett et al., 1992; Ito et al., 2001; Reichert et al., 1991 and Stillborg, 1984)。岩锚和承受层压的,不连续的,有裂隙和节理的岩体结合在一起。锚杆支护不仅加强或稳定节理岩体,同时也对岩体刚度有着显着的影响(Chappell, 1989)。锚杆的支护效果一个或几个机制相结合来实现的。锚杆通常作为一个组合梁来增加应力和节理处的摩擦强度,固定松散岩块或分层岩床(Franklin and Dusseault, 1989)。锚杆加固岩石是通过岩石间的摩擦作用,悬吊形态,或摩擦作用和悬吊两者兼有而实现的。基于这个原因,锚杆技术在支护巷道方面的应用可以适用所有岩石类型的(Panek and McCormick, 1973)。一般来说锚杆可用于增加由于直径低势力的支持和锚杆材料的强度。它们使高速贴壁将在更紧密的锚杆间距使用。他们的设计可以用来机械夹紧或对岩石进行水泥注浆(Aldorfand Exner,1986)。锚杆锚固系统通常是指固体或管状型钢安装在松散或坚实岩体中(Stillborg,1986年)。按照其锚固系统,锚杆可分为三个主要类型(Franklin and Dusseault, 1989;Aldorfand Exner, 1986; Hoek and Wood, 1989; Cybulski and Mazzoni, 1989)。第一类是机械岩锚,它可以分为两类:楔缝式锚杆,外壳膨胀锚杆。它们被安装在锚杆上的一部分,具体是在楔形夹紧的锚杆螺纹部分或者是夹紧部分。第二类是摩擦岩锚,它可以简单地分为两类:分节锚杆和膨胀锚杆分为锚杆。摩擦锚杆锚固岩体是由外露锚杆和钻孔的摩擦力完成的。最后一类是充分注浆锚杆,它也可分为两小类:水泥注浆锚杆,树脂锚杆。注浆锚杆(桩)是一种无机械锚定,通常包括一个带肋钢筋,该钢筋被安装在一个钻孔里面并和超过其全长的岩体结合(Franklin and Dusseault, 1989)。特别要注意的是水泥注浆锚杆和螺栓(胶合,树脂)是根据合成树脂锚杆适当调整固定的。锚固螺栓要与连杆螺栓和水泥的密封粘结以及用来拴紧螺栓的岩体相适应。合成树脂(树脂锚杆)和水泥砂浆(钢筋混凝土锚杆)可以为这种类型的锚杆使用。这些锚定锚杆可以被固定在所有类型岩石中。锚定杆体可以用多种材料制造,如带肋钢筋,光面钢筋,锚索和其他特殊处理的材料(Aldorfand Exner, 1986)。注浆锚杆广泛应用于矿井中的掘进,巷道,平巷和井筒的支护和加强其外围的稳定性。与其它替代品相比较,注浆锚杆安装的简单性,多功能性和相对低成本性则会取得更多的效益(Indraratna and Kaiser,1990)。当岩石开始移动和扩张时,锚杆会自动拉紧。因此,在开凿巷道后,岩体开始变形和已经失去联动性和剪切强度之前要尽快安装这些锚杆。虽然只有几种水泥浆类型可以适用,但是在现场许多应用中这些类型水泥浆已经足够,例如在被测得有短暂稳定期,用简单的波特兰水泥注浆加固销钉措施的岩体中应用。通过倾斜着向钻孔里面快速注满灰泥浆,它们可以被安装在已经拉紧的杆体中。保留的销子最终以简单的形式形成了锚孔,或用棉花包装废弃物,钢丝绒,或木楔子(Franklin and Dusseault, 1989)。混凝土锚杆是用水泥砂浆作为粘结介质。在最低低于水平面158的钻孔里面,砂浆很容易注入,然而在逐渐升高钻洞中,各种锚杆或其他设
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