钱营孜煤矿2.4 Mta新井设计含6张CAD图.zip
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钱营孜煤矿2.4
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英文原文Effect of grout properties on the pull-out load capacity of fully groute rock boltA. Klc, E. Yasar*, A.G. CelikDepartment of Mining Engineering, C ukurova University, 01330 Balcal, Adana, TurkeyReceived 30 October 2001; received in revised form 30 April 2002; accepted 24 May 2002AbstractThis 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 formulaehave 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 ofthe grouting material, the bolt length, the bolt diameter, the bonding area and the curing time ofthe 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 ofdisturbed 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 etal., 1991 and Stillborg, 1984). Rock bolt binds together a laminated, discontinued, fractured and jointed rock mass. Rock bolting not only strengthens or stabilizes ajointed rock mass, but also has a marked effect on therock 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 forstrengthening ofmine roadway and tunnelling in all type ofr ock (Panek and McCormick, 1973).Generally rock bolts can be used to increase the support of low forces due to the diameter and the strength ofthe 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 ofr ock 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; Aldorf and 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 ofthe outer covering ofbolt 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 thestabilisation oftunnelling, 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 ofshort 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 of 15。Below the horizontal plane, the mortar can simply poured in,whereas in raising drill holes (roof anchoring ) various design ofbolts 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 ofthe zone ofoverstr essed 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 ofcement-gr outed 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 (Aldorfand Exner, 1986): (1) where kb, safety coefficient (usually kbs1.5); 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 (carboniferous rocks and polyester resins C2=3 MPa). (3)where C3, shearing strength of the bonding material.The maximum (ultimate) bearing capacity of the bolt (P m) will be the lowest value from P1mto P111m.Bearing capacities ofall 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 thatPmsPm (4)where Pms, the ultimate bearing capacity o fthe bolt with respect ofthe tensile strength ofthe bolt material; Pm, the ultimate bearing capacity ofthe 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 (wyc) and bolt bond strength (tb) (Fig. 7), mechanical properties of grout material and bolt bond strength (tb) (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 ofr ebars (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 ofPortland cement with a water to cement ratio of0.34, 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 N100 mm;500 mmM and fly ash N10 mm; 200 mmM were added in a proportion of10% ofcement 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 2 mm (Schack et al., 1979). The Youngs modulus of the grouts was measured during unconfined compression tests and shear strength was calculated by means ofring shear tests.The test set-up is illustrated schematically in Fig. 1 and the procedure is explained below: After filling prepared grout mortar into the hole, bolt is inserted to the centre ofdrilling hole. After curing time, the rebars in the rock were axially loaded and the load was gradually increased until the bolt failed. The bond strength (tb) was then calculated by dividing the load (Pb) by surface area (Ab) ofthe bolt bar in contact with the grout. 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 ofa rock bolt can be formulated as follows (Littlejohn and Bruce, 1975): (5)where tb, ultimate bolt bond strength (MPa); Pb, maximum pull-out load ofbolt (kN); db, bolt diameter (mm); l , bolt length (cm); pdb lb ,bonded area (cm2).Fig. 1. Pull-out test set-up ofr ebar.3.2. Analysis of laboratory test results3.2.1. Influence of the bolt materialBolt diameters of10, 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 observationswere:（1）The maximum pull-out load (Pb) increases linearly with the section of the bolt while embedment length was constant.Fig. 2. Influence of the bolt diameter on the pull-out load of bolt.Fig. 3. Influence ofthe bond area on the pull-out load ofbolt.（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 ofbolt bond strength were calculatedbetween 5.68 and 5.96 MPa (Table 1).Bolt lengths of15.0, 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 ofthe bolt. （7） (2) Maximum pull-out strength ofa bolt is limited to the ultimate strength ofthe bolt shank.Table 1Influence of the bolt diameter on the bolt strengt (mm) (mm) () () (kN) (MPa)1012141618202224262824.224.276 9110612213743.254.759.273.681.65.686.015.586.035.96Rock: Basalt; curing time: 35 days; wc0.40; 8.15 MPa.Fig. 4. The pull-out test set-up of different bolt length.Fig. 5. The relationship between bolt length and pull-out load. Fig. 6. The relationship between bolt bond area and pull-out load.Table 2Influence of the bolt length on the bolt bond strength (cm) () (KN) (MPa)15.024.727.030.032.057 9310211312144.372.879.090.291.77.777.837.757.987.58Rock: Basalt; db12 mm; curing time: 21 days; tg: 10.4 MPa; UCSgs5.5 MPa; Eg7.54 GPa.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 ofthe mixing water is consumed by the hydration ofcement 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-termstrength by irregular stress distribution (Neville, 1963;Atis；1997). To obtain a plastic grout, bentonit clay can be added in a proportion ofup 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, ifused at all, shouldbe used with caution and in the correct quantities to avoid harmful side effect such as weakening and corrosion（Frannlin 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) ofgr out in high wyc 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 wyc 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).Table 3The influence of the water to cement ratio on the bolt bond strengthw/c (MPa) (MPa) () (KN) (MPa)0.340.360.380.4042.038.933.332.011.911.310.710.310210210210280.979.077.475.37.937.757.597.38Rock: Basalt; db=12 mm.Fig. 7. The influence of water to cement ratio on the bolt bond strength.Fig. 8. The influence of water to cement ratio on the bolt pull-out load.The bond strength of fully 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 ofgr outing materials on the bearing capacity ofbolt can be described as follows:(1) The uniaxial compressive and shear strength of the grouting materials has an important role on the behaviour ofr ock bolts. It was observed that increasing shear strength ofthe 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 ofthe grouted bolts. （9）(3) In Fig. 11 and Table 4 show that there is another relationship between Youngs modulus ofgr out and bolt bond strength. Increasing the Youngs modulus increases bolt bond strength. （10）Table 4Influence of the mechanical properties of the grouting materials on the bolt load capacity注浆类型(MPa)(GPa)(MPa) (kN) () (MPa)/ fly fly White cemen 5.3012.8417.7420.8022.9431.6030.5833.3337.7232.0133.3338.9442.001.152.742.963.393.796.224.895.256.637.408.059.129.302.044.996.227.959.176.737.348.058.1510.3010.7011.3011.9316.5343.7555.2857.5959.8455.4558.1556.0158.1575.2677.3978.9980.878484848484838383831021021021021.945.206.636.837.146.736.326.737.037.347.547.757.950.951.041.070.860.781.000.860.840.860.710.700.680.67Curing time: a1 day; b3 days; c5 days; d7 days; e14 days; f21 days.Fig. 9. The relationship between grout shear strength and bolt bond strength.Fig. 10. The relationship between UCS ofgr out materials and bolt bond strength.Fig. 11. Changing ofbolt bond strength due to Youngs modulus ofgr out.3.2.3. Influence of the curing timeAn important problem in the application ofcementgrouted bolts is the setting time ofthe mortar, which strongly affects the stabilizing ability of bolt. Cementgrouted dowels cannot be used for immediate support because ofthe time needed for the cement to set and harden (Franklin and Dusseault, 1989).In the pull-out tests, eight group of bolts having same length and mortar with a water to cement ratio of 0.4 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 ofbolt 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 orgroutrock 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 betweenrock bolt and rock and the mechanical properties of grouting materials.Fig. 12. Changing ofpull-out load ofbolt due to curing time.Fig. 13. Changing ofbolt bond strength due to curing time.Table 5The influence of the setting time on pull-out resistance凝结时间(days)(mm)(cm)()(KN)（MPa）13571421283512121212121212124.224.2919191919191919117.6443.7556.8371.2575.4876.5578.4680.061.944.796.227.858.368.468.668.77Rock: Basalt; wycs0.40; dds22 mm.4. ConclusionsThe laboratory investigation showed that the bolt capacity depends basically on the mechanical properties ofgr outing materials which can be changed by water to cement ratio, mixing time, additives, and curing time.Increasing the bolt diameter and length increases thebolt bearing capacity. However, this increase is limited to the ultimate tensile strength ofthe bolt materials. Mechanical properties ofgr outing 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 ofthe 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 of19 kg/cm2 in first day,77 kg/cm2 in 7 days and 86 kg/cm2 in 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, ofwhich the mechanical behavior is observed by shear spring.This explains the development ofbolt bond strengthand 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 ofr ock bolts.AcknowledgmentsThe authors would like to thank the Research Fund of Cukur ova University for supporting this research.No. FBE.2000.YL.50.ReferencesAtis, C.D., 1997. Design and properties ofhigh volume fly ash concrete for pavements. Ph.D. Thesis. The University of Leeds,UK, p. 342.Aldorf, J., Exner, K., 1986. Mine Openings: Stability and Support.Elsevier, Oxford, Amsterdam, Tokyo.Chappell, B.A., 1989. Rock bolts and shear stiffness in jointed rock mass. J. Geotech. Eng. 115.Cybulski, J.A., Mazzoni, R.A., 1989. Roofsupport systems continue to evolve. 12th Annual Institute on Coal Mining Healthy, Safety and Research, Blacksburg, Virginia, 147158.Franklin, J.A., Dusseault, M.B., 1989. Rock Engineering. McGraw-Hill Publishing Company, New York.Hoek, E., Wood, D.F., 1989. Rock Support. Min. Mag. 282287.Hyett, A.J., Bawden, W.F., Reichert, R.D., 1992. The effect of rock mass confinement on the bond strength of fully grouted cable bolts.Int. J. Rock Mech. Min. Sci. Geomech. Abstr. 29, 503524.Indraratna, B., Kaiser, P.K., 1990. Design for grouted rock bolts based on the convergence control method. Int. J. Rock Mech. Min. Sci.Geomech. Abstr. 27, 269281.Ito, F., Nakahara, F., Kawano, R., Kang, S., Obara, Y., 2001.Visualisation off ailure in a pull-out of cable bolts using X-ray CT. Construction Build. Mater. 15, 263270.Kaiser, P.K., Yazici, S., Nose, J., 1992. Effect of stress change on thebond strength off ully grouted cables. Int. J. Rock Mech. Min. Sci.Geomech. Abstr. 29, 293305.Littlejohn, G.S., Bruce, D.A., 1975. Rock anchors-state ofthe art.Design Ground Eng. Part 1, 2548.Neville, A.M., 1963. Properties ofConcr ete. Unwin Brothers Ltd,London, pp. 532.Panek, L.A., McCormick, J.A., 1973. Roofyrock bolting. SME Mining Engineering Handbook I, 13-125y13-135, New York.Reichert, R.D, Bawden, W.F., Hyett, A.J., 1991. Evaluation of design bolt bond strength for fully grouted bolt. 93rd Annual Meeting of CIM, Vancouver.Schack, R., Garshol, K., Heltzen, A.M., 1979. Rock Bolting: A Practical Handbook. Pergamon Press, Oxford, pp. 84.Stillborg, B., 1986. Professional users for rock bolting. Ser. Rock Soil Mech. 15.Stillborg, B., 1984. Experimental investigation ofsteel cables for rock reinforcement in hard rock. Doctoral Thesis. 33 D, Lulea University, Sweden.中文译文水泥浆性能对充分注浆锚杆拉拔承载能力的影响A. Klc, E. Yasar*, A.G. CelikDepartment of Mining Engineering, C ukurova University, 01330 Balcal, Adana, TurkeyReceived 30 October 2001; received in revised form 30 April 2002; accepted 24 May 2002摘要本文阐述了为工程运作而开发的一种安全，实用和经济支持系统的项目成果。在岩石工程中没有被拉紧且被水泥充分注浆的锚杆已经使用了多年。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能力的影响研究很少。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实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能力的力学性能的影响已被数量化，而且，为了计量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 etal., 1991 and Stillborg, 1984)。岩锚和承载受压的，不连续的，有裂隙和节理的岩体结合在一起。锚杆支护不仅加强和稳定节理岩体，同时也对岩体刚度有着明显的影响(Chappell, 1989)。锚杆的支护效果是通过一个或几个的机制相结合实现的。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，固体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磨擦作用，悬吊形态，或悬吊形态和磨擦作用两者兼有实现的。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的岩石类型(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。它们的设计可以用来机械夹紧或对岩石进行水泥注浆(Aldorf and 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)。按照其锚固系统，锚杆可分为三个主要类型(Franklin and Dusseault, 1989; Aldorf and 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。它们可以由楔形夹紧部分或螺纹夹紧的一部分固定在锚定部分。第二部分是摩擦岩锚，它可以简单地分为两类：管缝式锚杆和膨胀式锚杆。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，它也可以分为两小类：水泥注浆锚杆，树脂锚杆。 注浆锚杆（桩）锚固是一种无机械锚定，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栓紧螺栓的岩体相适应。合成树脂（树脂锚杆）和水泥砂浆（钢筋混泥土锚杆）可以为这种类型的使用。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(Aldorf and Exner, 1986)。注浆锚杆广泛应用于矿井的掘进，巷道、平巷和井筒的支护和加强其外围的稳定性。与其他替代品相比较，注浆锚杆的简单性，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，在开掘巷道后，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。虽然中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凝结介质。在最低低于158的钻孔里面，砂浆很容易注入，然而在逐渐升高钻洞中，各种锚杆或其他设备的设计则会用来水泥砂浆流出(Aldorf and Exner,1986)。 充分水泥注浆锚杆承载能力取决于锚杆直径，锚杆长度，岩石和水泥浆的强度。这种充分注浆锚杆的锚固强度最初是靠摩擦力的，因此取决于锚杆和水泥，水泥和岩体两个层面的剪切强度。因此，在这个界面的剪切强度的任何变化都将影响锚杆的锚固力和其承载能力。实施实验室的测试方案的目的是评估在水泥注浆锚杆和锚杆界面上剪切强度的变化对锚固力的影响，并且该实验测试结果证实了这一理论。2解决方案相对于过分受压区或屈服区的岩体来说，一个锚杆的有效性取决于其长度。一个锚杆剪切应力和轴向应力的分布也关系到有效锚杆长度，因为应力平衡必须由锚杆和围岩共同实现(Indraratna and Kaiser,1990).水泥注浆锚杆（Pb )的承载能力，锚固力是其粘结剂的凝聚力，围岩和锚杆体的函数。从而得到最终的锚杆(Pm)承载能力公式，表示如下(Aldorfand Exner, 1986)： (1)式中是安全系数（通常取1.5）；是作用在锚杆上的粘结材料的粘结力；，锚杆长度；，锚杆直径。 (2) 式中，钻孔直径，粘结材料与围岩之间的凝聚力（=3Mpa） (3)式中为粘结材料的剪切强度。 螺栓的最大承载能力将是从到的最低值。 所有类型的锚杆承载能力都必须从锚杆材料的拉伸强度（）的角度进行评估，且由于锚杆在锚孔中的锚固力，这种拉伸强度必须不得超过极限承载能力。它认为 （4） 式中考虑到锚杆材料抗拉强度时的极限承载能力；，锚杆的极限承载能力。3实验室研究3.1实验拉拔实验是在实验室用水泥砂浆对玄武岩块注浆。通过简单的拉拔实验方案我们评估了锚杆直径（）和锚杆拉应力（以计）（图2），锚杆面积（）和锚杆拉应力（）（图3），锚杆长度（）和锚杆拉应力（）（图5），水灰比（w/c）和锚杆粘结强度（）（图7），注浆材料的机械性能和锚杆粘结强度（）（图9，图10和图11），固化时间（天）和锚杆强度（图12和13）之间的关系。这些样本包括了和玄武岩岩块固结在一起的钢筋（成对的直径在10-18mm）。所用的这些玄武岩块的杨氏模量是27.6Gpa和单轴抗压强度133兆帕（USCg）。钻孔的深度是15-32cm，要求钻孔的直径是20-28cm，比锚杆直径大10mm。锚杆被水泥砂浆注浆。该水泥浆是各种不同水灰比的硅酸盐水泥混合组成的，不同的水灰比有0.34,0.36,0.38和0.40，凝结时间为28天。为了获得具有不同的力学性能不同类型的水泥浆，将500m，100m的硅质砂；粉煤灰10m，200m加入到水泥重量占10%，水灰比为0.40的白水泥浆中。沙粒应很好的分级，最大晶粒尺寸为2毫米（施克等人，1979）。杨氏模量的测量是在无限压缩试验中进行，同时抗剪强度由环刀实验方法计算。该实验的图解说明如图1. 程序说明如下（1） 在将水泥砂浆注入钻孔之后，锚杆被插入到钻孔中心。（2） 过了凝结时间后，在岩体中的钢筋承受轴向载荷，逐渐加大载荷直到锚杆被拉断。（3） 负载（）除以注浆锚杆接触表面积（）计算得到粘结强度（）。（4） 以不同类型的水泥浆，锚杆尺寸和固化时间重复拉拔实验。锚杆直径和粘结面积对锚杆粘结强度的影响可以公式化，公式如下（利特尔约翰和Bruce，1975）： （5）式中，为锚杆极限承载力（MPa）；为锚杆承受的最大载荷（KN）；锚杆长度（cm）；粘结面积（）图1 锚杆拉拔实验3.2实验结果分析3.2.1锚杆材料的影响在实验中分别用了直径为10,12,14,16,18的锚杆典型的结果如表1，图2和3。最重要的结论是：表1 锚杆直径对锚杆强度的影响 (mm) (mm) () () (kN) (MPa)1012141618202224262824.224.276 9110612213743.254.759.273.681.65.686.015.586.035.96 Rock: Basalt; curing time: 35 days; w/c=0.40; =8.15 MPa.图2锚杆直径对锚杆强度的影响图3粘结面积对锚杆拉拔承载能力的影响（1） 当埋设长度为常数时，最大拉应力（）与锚杆截面呈线性增加。（2）锚杆截面取决于锚杆的直径。锚杆直径和锚杆承载能力的关系可以由如下经验公式解释（图2）= （6）（3）锚杆粘结强度值在5.68和5.96 之间计算兆帕（表1）。如图4所示，实验中的锚杆长度分别是15.0,24.7，27.0,30.0和32.0cm。经典结果显示在表2中，图5和图6中，最重要的结论是：（1）锚杆的拉拔力和其插入深度呈线性增加趋势。 (7)（2） 锚杆的最大拉拔强度受限于后期锚杆的极限强度。图4 不同锚杆长度的的拉拔实验图5 锚杆长度和承受载荷之间的关系图6 锚杆截面积与拉拔承载能力的关系表2锚杆长度对锚杆强度的影响 (cm) () (KN) (MPa)15.024.727.030.032.057 9310211312144.372.879.090.291.77.777.837.757.987.58Rock: Basalt;=12 mm; curing time: 21 days; : 10.4 MPa; =35.5 MPa; =7.54 GPa.3.2.2水泥材料的影响在重量上，水灰比应不超过0.40，过多的水会严重降低水泥的长期强度。因为，在水泥水化中消耗了部分混合水。其余的混合水蒸发，然后毛细管孔隙水不均匀分布在砂浆内部。因此，这种结构可以阻止长期强度应力分布的不均与性(Neville, 1963;Atis, 1997)。要获得塑性水泥浆，膨润土粘土可以添加到高达2%的重量比例的水泥中。其他添加剂可加速调剂时间，实现了在较低水灰比条件下注入并水泥浆流动性，使注浆膨胀并施压钻孔。如果选择使用添加剂，就谨慎使用，选择准确的数量，从而避免其不利的副作用，例如削弱和腐蚀（Franklin and Dusseault, 1989)。水泥浆的水灰比大大影响锚杆的拉拔强度。从表3中可以看出，抗剪切强度在水灰比高时得到较低的值，反之相反。水灰比在0.34和0.40之间则会取得最好的结果。尽管当水灰比为0.34是粘结强度最大，水泥浆的可输送性下降，同时会出现一些应用中的困难。在高水灰比情况下，对钻孔进行水泥浆材料的输送很容易，但是粘结强度会降低（图7和图8）。图7水灰比对粘结强度的影响图8水灰比对锚杆拉拔承载能力的影响表3水灰比对锚杆粘结强度的影响w/c (MPa) (MPa) () (KN) (MPa)0.340.360.380.4042.038.933.332.011.911.310.710.310210210210280.979.077.475.37.937.757.597.38Rock: Basalt; db=12 mm.充分注浆锚杆的锚固强度最初是靠摩擦力的，从而取决于锚杆和水泥，水泥和岩体两个层面的剪切强度。因此，在这个界面的剪切强度的任何变化都将影响锚杆的锚固力和其承载能力。这种由于使锚杆承载能力发生变化的注浆材料力学性能造成的影响可以如下描述：（1）注浆材料的单轴抗压强度和卡抗剪强度对锚杆的表现起着重要作用。据观察，注浆材料抗剪强度与与锚杆的粘结强度成对数关系。如表4和图9中所示。把这种注浆材料和锚杆强度之间的关系公式化，可以得到如下公式： (8)（2）从表4和图1
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