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1.
隧道围岩全长黏结式锚杆界面力学模型研究 总被引：3，自引：0，他引：3
分析围岩弹塑性介质中全长黏结式锚杆的锚固界面层应力分布和变化特征,对研究隧道工程初期支护系统的力学效应具有重要意义。根据全长锚杆微段的受力平衡以及锚固界面层剪应力的传递机制建立了关于锚杆轴向位移的微分方程,通过求解锚杆轴向位移的微分方程可得到锚杆与围岩相互作用下的轴向载荷和锚固界面剪应力的分布函数。然后将锚杆界面剪应力对围岩的支护反力转化为圆形隧道轴对称径向体积力,进而求解有锚喷支护作用下圆形隧道围岩塑性区半径。在此解析模型基础上,可对隧道围岩-支护系统进行详细的分析和评判。算例分析表明,初期支护时机的选择对锚固效应和围岩稳定性有较大影响;适当增加全长黏结式锚杆的锚固层厚度能明显降低锚杆端部剪应力的应力集中度,能有效改善锚杆的锚固效果。 相似文献
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以大型地下洞室为背景,采用隐式锚杆柱单元模拟黏结式岩石锚杆,推导了杆体对围岩模型的附加刚度贡献模型。根据中性点理论,假定锚固体界面的剪切滑移模型,导出了锚杆与围岩相互作用下的荷载传递基本微分方程。基于三维弹塑性有限元增量法计算的围岩离散位移,采用插值拟合获得造成锚杆变形的围岩连续位移,通过求解微分方程得到锚固体界面剪应力和轴向力分布函数。将获得的锚固体剪应力采用等效附加应力模型作用于岩体,反映了锚杆的支护效应。实例分析表明,锚杆新算法能较好地模拟锚杆支护效果。获得的锚固体受力分布特征符合中性点理论,锚固体界面剪应力分为正、负两段,锚固体轴向力分布为单峰曲线。此外,新方法的计算值与实测值较为接近。 相似文献
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建立了管缝式锚杆在拉拔荷载作用下的受力分析模型,该模型能够反映锚杆破坏的渐进过程。分析表明,在拉拔荷载作用下管缝式锚杆在荷载作用点最先发生相对滑移,且随着荷载的增加滑移段的长度逐渐增加,直到整根锚杆与围岩发生相对滑移。根据能量守恒原理得到了管缝式锚杆在安装入钻孔后对围岩径向作用力的计算公式。对管缝式锚杆进行了非局部摩擦分析,得到了基于非局部摩擦模型的管缝式锚杆界面剪应力分布。研究了管缝式锚杆直径对锚杆界面剪应力分布的影响,同时得到了锚杆最大抗拉拔力与锚杆长度之间的关系。将理论模型预测值与试验结果对比,验证了理论模型的有效性。 相似文献
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在矿山、水利、交通等工程领域中大变形锚杆已经获得了广泛的认可和应用,而相应理论水平落后于工程实践的现状则限制了大变形锚杆支护技术的进一步发展。针对大变形锚杆的力学及变形特性,提出了一种锚杆-围岩耦合作用结构模型,并基于塑性增量理论,从锚杆-围岩相互作用的角度,提出了大变形锚杆加固岩体的求解方法,推导了加锚岩体的平衡方程、位移协调方程和锚杆响应方程。在Visual Basic开发环境中编制有限差分计算程序,利用龙格库塔法求得了大变形锚杆-围岩耦合模型的半解析解,并通过数值模拟验证了理论模型的有效性。基于上述理论模型和计算方法,不仅可以计算得到大变形锚杆轴力和剪应力分布情况,定量分析其支护效应,还可以系统地求得加锚岩体的地层响应曲线及锚杆自身的响应曲线,对于地下工程中大变形锚杆的支护设计有基础性指导意义。 相似文献
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锚固技术是岩土工程中的一个主要支护手段之一,如何揭示锚索（杆）与岩石的复合作用机制锚固和失效形态,越来越成为关注的焦点。采用FLAC数值方法,对大试块横向含锚岩体的单轴压缩条件下力学性态进行了试验研究,结果表明：锚索（杆）与围岩的复合增强机制不仅与外载的大小有关,而且与锚固界面的力学性质有很大关系。随着锚固界面凝聚力的减小,锚固界面和锚索轴向的应力值都将减少,即锚索（杆）增强承载能力下降。当凝聚力减小到一定数值时,锚索（杆）将脱黏而产生滑动,导致锚固失效,因此,提高锚固界面的黏结力是保证锚固效果的关键之一。大试块锚固体的实验室岩石力学试验无论是试块加工还是试验过程,将十分困难和繁琐。采用数值模拟方法代替实验室试验,具有省时、经济、可视性强等优点,是今后研究锚固体力学性态的重要途径,具有推广应用价值。 相似文献
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Development of Rock Bolt Elements in Two-Dimensional Discontinuous Deformation Analysis 总被引：1，自引：0，他引：1
Computer modeling can be used to explore and gain new insights into the impacts of rock bolt intersecting joints in rock masses, and to estimate the effectiveness of the rock reinforcement system. In order to achieve this goal, we couple a rock bolt element into the two-dimensional discontinuous deformation analysis (DDA2D) program. The coupling algorithm is based on the analytically-derived interface behavior between a rock bolt and the rock material for grouted rock bolts. The shear force generated by slippage along the interface is assumed to have a linear relationship with respect to the relative slipping distance between the rock bolt and the rock. The linear elastic criterion is applied to determine the material behavior of rock bolts before the axial stress reaches the yield value. The pullout tests are simulated to verify the coupling algorithm and the effects of the proposed rock bolt elements. Parametrical studies are also carried out to analyze the effectiveness of the rock bolts under various end conditions, joint locations and bond stiffness. In addition, the performance of the rock bolt during the interface debonding is analyzed using two types of constitutive laws, i.e., the friction law and the reduction law. The simulation results show that the proposed rock bolt models can predict the shear forces and axial loading along the rock bolts. 相似文献
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岩体锚固效应及锚杆的解析本构模型研究 总被引：3，自引：0，他引：3
利用Mohr-Coulomb、Hoek-Brown以及Duncan-Chang理论分别分析了块状和碎块状岩体锚固后的物理效应,通过分析认为,岩体锚固后可以有效地提高岩体的凝聚力和软弱结构面的抗剪强度,增强岩体的弹性模量,改善岩体的力学性质。通过对拉拔试验测试结果分析,在一定的假设条件下,推导了锚杆与注浆体或岩体耦合情况下的解析本构方程,并对其进行了参数分析,认为提高拉拔力、增大锚杆直径和锚固段长度可以有效地改善其锚固效果,并提出了锚固临界值的概念。在前人工作的基础上,利用提出的耦合解析本构模型建立了非耦合状态下锚杆的解析本构模型,通过计算认为,该解析模型是合理的。 相似文献
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剪切过程中锚杆的轴向和横向作用分析 总被引：1，自引：0，他引：1
为了分析锚杆轴向力和横向剪切力分别换算的结构面抗剪强度大小规律,依据最小势能原理的变分法,并考虑结构面剪胀特性,建立加锚结构面抗剪强度计算公式。通过加锚结构面直剪试验验证理论计算的有效性,结合理论计算公式,分析了在不同锚杆倾角下围岩强度、锚杆直径和法向应力对锚杆轴向力和横向剪切力换算的抗剪强度影响规律,以及预应力对抗剪强度的影响。结果表明：加锚结构面抗剪强度计算结果与试验结果吻合较好;当锚杆倾角逐渐增大时,锚杆轴向力发挥的抗剪强度逐渐降低,横向剪切力发挥抗剪效能逐渐增大,当锚杆倾角为120°～150°时,轴向力换算的抗剪强度基本为0,而横向剪切力换算的抗剪强度最大;随着围岩强度或法向应力的增大,锚杆轴向力换算的结构面抗剪强度减小,但随锚杆直径或预应力的增大,锚杆轴向力换算的结构面抗剪强度增大;当围岩强度和锚杆直径增大,锚杆横向剪切力换算的抗剪强度会明显增大,而预应力增大会使锚杆横向剪切力换算的抗剪强度呈现降低趋势。 相似文献
10.
Haijian Su Hongwen Jing Honghui Zhao Liyuan Yu Yingchao Wang 《Environmental Earth Sciences》2017,76(4):179
Rock mass in the fault fracture zone has some characteristics such as low strength and poor self-stability, so the control mechanism of stability has been a difficulty in the research of underground engineering. A set of laboratory simulation method of fault fractured rock mass is developed to reflect the natural forming process of fault fracture zone. Compared with intact rock mass, the fault fractured rock mass has an obvious degradation in strength and deformation parameters, and the degradation index is between 22.79 and 84.06%. The bolt has a certain supporting effect on the fault fractured rock mass, and in the situation of end anchoring, the greater the pretightening force is, the better the enforcement effect will be. The stress field produced by high pretightening force can relieve the stress concentration around the bolt hole and make the initial cracks of rock mass away from the bolt plate. The evolution curve of bolt axial force in the process of uniaxial compression of large-scale specimen shows four stages, which are the initial compression stage, pre-peak joint load-bearing stage, post-peak joint load-bearing stage and the residual stage. Research results could provide some theory reference for the stability control of rock mass in the fault fracture zone. 相似文献
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小净距隧道中夹岩受到两侧开挖的剧烈扰动,处于单向或双向受力的不利状态,严重影响施工安全,而预应力全长注浆对拉锚杆常用于中夹岩的主动支护。为阐明对拉锚杆的作用模式和控制机制,建立相应的力学模型和解析方法,开展实测验证,并进行参数分析和工程应用。研究表明：对拉锚杆为中夹岩提供强力水平约束,并提高岩体力学性能,发挥挤压加固作用;对拉锚杆利用剪切摩阻改善浅层围岩受力状态,同时锚固深部岩体,具有承载传力效果;对拉锚杆轴力和剪应力均由两侧向中间非线性衰减,作用范围局限于浅层中夹岩,实测结果验证了理论方法的合理性;进行了对拉锚杆的参数分析,提出了对拉锚杆临界长度、合理锚杆直径等工程建议;结合京张高铁长城站小净距隧道实践,主动增强对拉锚杆设计参数,变更后围岩压力、拱顶沉降和水平收敛的实测均值分别降低12.2%、14.1%和10.2%,保障了隧道开挖的安全。 相似文献
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为了研究锚杆对节理剪切性能的作用机制和模式,开展了锚固节理岩体的实验室剪切试验,模拟了不同强度的岩体在剪力作用下的变形和受力特征,对比了锚杆加固前、后岩体的剪切变形规律,分析了节理岩体强度、预应力及锚固方式对节理的抗剪能力的影响,试验过程中通过应变片测点监测锚杆轴力的变化规律,研究了节理剪切过程中锚杆的轴向受力机制和变形特性。剪切试验完成后,取出剪切变形后的锚杆,统计了变形段长度与各参数之间的关系。通过试验结果分析,剪力-位移曲线存在明显的3个阶段：弹性阶段、屈服阶段和塑性强化阶段,曲线近似呈现双直线特征,弹性段锚杆主要发挥销钉作用;屈服段锚杆的轴向作用开始调动,锚杆同时存在销钉和约束作用;塑性段锚杆不再发挥销钉作用,只是依靠其轴向约束作用限制岩体的变形;曲线表现出韧性增强的剪切性能,这就使得锚杆锚固节理岩体的破坏特性由脆性转变为塑性,从而提高了岩体的稳定性和安全度。节理面的滑动对锚杆产生剪切作用,由于切向变形而产生了附加的锚杆轴向变形,锚杆的轴向应力随着剪切位移的增大呈增长的趋势,变形剧烈区域集中于节理面附近,且距离节理面越近其轴向应力增大越多。 相似文献
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基于小波函数伸缩平移的特性,建立了能反映锚杆界面黏结?软化?滑动力学特性的剪应力?位移非线性本构模型,克服了三折线软化界面模型需要分段分析的复杂性。结合锚固体荷载传递的力学微分方程,推导了锚杆拉拔荷载?位移曲线的解析表达式,并提出了锚固体位移、轴力、周边剪应力的数值计算方法和步骤。通过算例分析,得到不同张拉位移作用下的锚固段位移、轴力和剪应力分布,获得的锚杆拉拔荷载?位移和锚杆轴向力分布计算值与实测值进行了对比分析,验证了该方法的有效性。该方法能准确地反映锚杆在不同荷载下的传力机制,模拟锚杆从弹性工作状态到塑性滑移的全过程。最后,通过参数分析,得到了锚杆锚固长度、轴向刚度以及锚固界面本构参数对锚固效果的影响规律。 相似文献
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预应力锚索加固边坡是提高边坡稳定性的重要手段。弄清预应力锚索加固边坡的机制对于指导边坡加固设计具有重要的理论意义。通过建立高陡边坡计算模型,不断提高边坡岩土体强度折减系数,得到了边坡坡脚位移及预应力锚索内力变化规律,并结合预应力锚索加固岩体应力分布规律,得到了有益的结论：（1）边坡岩土体强度折减系数超过边坡安全系数后,预应力锚索内力开始迅速增加,越靠近坡脚的预应力锚索,内力增加越明显,可以监测坡脚处锚索内力变化,评价边坡稳定状态;（2）对于高陡边坡,绝大部分预应力锚索并不能提高潜在滑动面上的压应力,不能提高滑动面的抗剪强度;（3）预应力锚索加固高陡边坡的主要机制在于限制边坡潜在滑动体的位移。 相似文献
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利用锚杆轴力量测定围岩破坏区的方法 总被引：1，自引：0，他引：1
本文系统总结了锚杆轴力分布型式,分析了各轴力分布型式的力学机理。结果表明,在围岩不同区内,锚杆所受剪切力具有不同的特点,而且,锚杆所受剪切的特点在锚杆轴力分布中得到了反映。根据以上关系,提出了利用锚杆轴力量测确定围岩破坏区的方法。 相似文献
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Charlie C. Li 《Rock Mechanics and Rock Engineering》2016,49(1):273-289
An inflatable bolt is integrated in the rock mass through the friction and mechanical interlock at the bolt–rock interface. The pullout resistance of the inflatable bolt is determined by the contact stress at the interface. The contact stress is composed of two parts, termed the primary and secondary contact stresses. The former refers to the stress established during bolt installation and the latter is mobilized when the bolt tends to slip in the borehole owing to the roughness of the borehole surface. The existing analysis of the inflatable rock bolt does not appropriately describe the interaction between the bolt and the rock since the influence of the folded tongue of the bolt on the stiffness of the bolt and the elastic rebound of the bolt tube in the end of bolt installation are ignored. The interaction of the inflatable bolt with the rock is thoroughly analysed by taking into account the elastic displacements of the rock mass and the bolt tube during and after bolt installation in this article. The study aims to reveal the influence of the bolt tongue on the contact stress and the different anchoring mechanisms of the bolt in hard and soft rocks. A new solution to the primary contact stress is derived, which is more realistic than the existing one in describing the interaction between the bolt and the rock. The mechanism of the secondary contact stress is also discussed from the point of view of the mechanical behaviour of the asperities on the borehole surface. The analytical solutions are in agreement with both the laboratory and field pullout test results. The analysis reveals that the primary contact stress decreases with the Young’s modulus of the rock mass and increases with the borehole diameter and installation pump pressure. The primary contact stress can be easily established in soft and weak rock but is low or zero in hard and strong rock. In soft and weak rock, the primary contact stress is crucially important for the anchorage of the bolt, while in hard and strong rock it is the secondary contact stress that plays a vital role. 相似文献
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Explanation for the widely reported observation that fully grouted reinforcement is more effective in hard rock that behaves as a discontinuum than in soft rock is presented. Analytical solutions are presented for the distribution of displacement and load along an untensioned fully grouted elastic bolt, of specified bond stiffness, which is activated during excavation by either a continuous or discontinuous distribution of rock displacement. The results indicate that significantly higher axial loads are developed for the discontinuous case. Since the mechanics of bond failure depend on the type of bolt and grout used, in the second part of the paper a finite difference formulation is introduced and combined with a non-linear model for the bond behaviour of a cement grouted seven-wire strand cable bolt. The results of a parametric study indicate that, because the bond is frictional and depends on confinement at the borehole wall, for the same profile of rock mass displacement lower loads are developed in soft rock. Furthermore, in soft rock, excavation induced stress changes can cause a dramatic reduction in bond strength, so that, even after significant rock mass displacement, the axial load developed is significantly less than the tensile strength of the cable. A combination of these effects can explain why failures of cable bolted ground involve debonding at the cable–grout interface in soft rock, and why instances of cable rupture are confined to hard, blocky rock masses. 相似文献
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Analytical‐numerical solution for stress distribution around tunnel reinforced by radial fully grouted rockbolts 
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下载免费PDF全文 This paper presents an analytical‐numerical approach to obtain the distribution of stresses and deformations around a reinforced tunnel. The increase in the radial stress of the reinforced tunnel, based on the performance of a bolt, is modeled by a function, which its maximum value is in the vicinity of the bolt periphery and it exponentially decreases in the far distance from the bolt. On the basis of this approach, the shear stiffness between the bolt and the rock mass and the shear stress distribution around the bolt within the rock mass are also analytically obtained. The results are compared with those obtained by the assumption of ‘uniform increase of radial stress’ method, which is made by the previous studies. The analyses show when the bolts' spacing is large, the safety factor must be increased if the ‘uniform increase of radial stress’ method is used for the design. Finally, a procedure is introduced to calculate the non‐equal deformation of the rock mass between the bolts at any radius that can be useful to compute the bending moment in shotcrete layer in New Austrian Tunnelling Method (NATM) approach. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献