Strength characteristics of rock anchored by NPR bolt with different preloads

This study compares the strength characteristics of rocks anchored by NPR bolts and ordinary bolts with varied preloads,based on the mechanical properties of NPR bolts(with a negative Poisson’s ratio).The results show that the uniaxial compressive stress-strain curve of ordinary anchored rocks exhibits noticeable abrupt changes.After reaching peak strength,the bolt breaks,whereas the stress-strain curve of NPR-anchored rocks is smoother.The NPR bolt enters the stage of continuous resistance after reaching maximal strength and does not break.As the preload increases,the strength of the anchored rock grows linearly.A calculation equation for the strength of the anchored rock is proposed based on the preload.The theoretical equation fits the test results well,and the fitted parameters show that NPR bolts can better increase the strength of the rock.The concept of dynamic toughness UC of anchored rock is proposed to reflect the comprehensive mechanical properties of anchored rock,including strength and plasticity.As the preload increases,the UC of ordinary anchored rock first decreases and then increases,while the UC of the NPR anchored rock does not change significantly with the preload when the strain is small,and the UC increases with the increase of the preload when the strain is large.

Anchoring mechanism and application of hydraulic expansion bolts used in soft rock roadway floor heave control

Comparing with the resin bolt, the hydraulic expansion bolt has different anchoring mechanism and application advantage. According to the working mechanism of the hydraulic expansion bolt, its anchoring force is expressed in four forms including support anchoring force, tension anchoring force, expansion anchoring force and tangent anchoring force, and their values can be obtained on the basis of each calculation formula. Among them, the expansion anchoring force, which is the unique anchoring force of the hydraulic expansion bolt, can provide confining pressure to increase the strength of rock. Aiming at solving the problem of stability control in the soft rock roadway in Jinbaotun Coal Mine which has a double layer of 40 U-type sheds and cannot provide enough resistance support to control floor heave, the study reveals the mechanism of floor heave in the soft rock roadway, and designs the reasonable support parameters of the hydraulic expansion bolts. The observed results of floor convergence indicate that the hydraulic expansion bolts can prevent the development and flow of the plastic zone in the floor rock to control floor heave. Research results enrich the control technology in the soft rock roadway.

Anchoring eccentricity features and rectifying devices for resin grouted bolt/cable bolt

The anchoring eccentricity of the bolt and cable bolt is a common problem in geotechnical support engineering and affects the ability of the bolt and cable bolt to control the rock mass to a certain extent.This paper reports on numerical simulation and laboratory experiments conducted to clarify the effect of eccentricity on the anchoring quality of the bolt and cable bolt,and to establish an effective solution strategy.The results reveal that the anchoring eccentricity causes unbalanced stress distribution and the uncoordinated deformation of the resin layer,which results in higher stress and greater deformation of the resin layer at the near side of the rod body.Additionally,as the degree of anchoring eccentricity increases,the effect becomes more significant,and the resin layer of the anchoring system becomes more likely to undergo preferential failure locally,which weakens the load-bearing performance of the anchoring system.This paper develops an innovative bolt anchoring rectifying device(B-ARD)and cable bolt anchoring rectifying device(C-ARD)on the basis of the structural characteristics of the bolt and cable bolt to better ensure the anchoring effect of them.The working effects of these two devices were verified in detailed experiments and analysis.The experimental results show that the anchoring rectifying devices(ARD)improve and ensure the anchoring concentricity of the bolt and cable bolt,which will help improve the supporting performance of them.The paper provides a convenient and effective method for improving the anchoring concentricity of the bolt and cable bolt,and provides a concept and reference for technical research on improving the effect of roof bolting.

Parameter analysis of anchor bolt support for large-span and jointed rock mass

In order to obtain the optimal parameters of anchor bolt supporting system for large-span and jointed rock mass in Kaiyang Phosphor Mine, it is expensive and unavailable with the method of in-situ experiments. This paper describes a numerical modeling with discrete element method for the supporting effects of different type of anchor bolts. The anchor bolts with variant length of 0.5m, 0.8m, 1.0m, diameter of 10mm, 15mm, 20mm, setting spacing of 3.0m, 2.5m, 2.0m, and setting angle of 10°, 20°, 30°, are simulated respectively. The results show that there exist optimal parameters of anchor bolt support for large-span and jointed rock mass. For the bolt support of the concerning, the optimal length is 2.53.5m, the diameter is 2535mm, the spacing is 0.50.6m, and the setting angle is 105°.

Numerical simulation of the effect of coupling support of bolt-mesh-anchor in deep tunnel

The mechanical effects of bolt-mesh-anchor coupling support in deep tunnels were studied by using a numerical method, based on deep tunnel coupling supporting techniques and non-linear deformation mechanical theory of rock mass at great depths.It is shown that the potential of a rigid bolt support can be efficiently activated through the coupling effect between a bolt-net support and the surrounding rock.It is found that the accumulated plastic energy in the surrounding rock can be sufficiently transformed by the coupling effect of a bolt-mesh-tray support.The strength of the surrounding rock mass can be mobilized to control the deforma-tion of the surrounding rock by a pre-stress and time-space effect of the anchor support.The high stress transformation effect can be realized by the mechanical coupling effect of the bolt-mesh-anchor support, whereby the force of the support and deformation of the surrounding rock tends to become uniform, leading to a sustained stability of the tunnel.

Vibration Characteristic of Anchoring System of Bolt and Elastic Wave Propagation Law

Based on one-dimension wave theory, the propagation law of elastic wave along the rock bolt, rock medium and their coupling system are researched, and the attenuation law and propagation mechanism of wave in the anchoring system are obtained. Meanwhile, the studies on end reflection and dynamic response under load are also carried out experimentally, the relationship between anchoring length and excited wave length is obtained when the end reflection of holt emerges, and it is concluded that under the condition of bolt loaded, as the load increases, the reflection of the upper interface of anchoring segment weakens while the end reflection strengthens relatively, hence the energy attenuation increases. These results provide some important theory basis for measuring the effective anchoring length of bolt, judging the bonding quality of anchoring end and surrounding rock, and estimating the utmost load force of bolt.

Analysis on the anchor mechanism of the full length resin bolt

The purpose of this paper is to reveal the stress distribution characteristic along the full length anchor bolt. Based on the mechanic model set up, the author calculated the anchor mechanism of the full length resin rock bolt. The stress distribution characteristic is different according to different type of surrounding rock. The conclusion is important to optimize the roadway bolt support design.

Applied on bolting-cable anchor support of full-seam roadway in weaker thick coal seam

The designing method and the supporting mechanism of both bolt and small cable anchor for full seam roadway in the weaker thick coal seam are systematically analyzed, and the construction technology and the supporting results are briefly summarized.

ANCHORING EFFECT ANALYSIS OF TENSIONED BOLTS

The paper analyses quantitatively the anchoring effect of tensioned bolts on surrounding rock strength, and defines two concepts: one is the surrounding rock strength increased amount Δτ13 and the other is the strength influence factor k. The anchoring effect of tensioned bolts is considered to increase a strength increased amount Δτ13 where Δτ13 is the product k and ten-sioned load p, i. e. Δτ13 = kp, where k is a function of two variables x and y. The distribu-tive properties both Δτ13 and k are also discussed in the paper, obtaining some useful results for designing bolting support parameters.

Anchorage Performance and Interfacial Mechanics Transfer Characteristics of a Composite Anchor Bolt with Different Surface Shape

To solve the deficiency of steel anchor blot in corrosion resistance and flaw of GFRP anchor bolt in fracture resistance, our research group develops a new composite anchor bolt made of steel strands wrapped up with compound fiber resin. To improve the cohesion performance of the composite anchor bolt, pull-out tests of different composite anchor bolts with different groove intervals and depths were made and analyzed. The results show that the pulling resistance of the composite anchor bolt increases with the increase of groove interval and depth, but groove interval and depth have optimal value. Based on elastic mechanics, the cohesion between anchor bolts and anchor bodies and its distribution characteristics caused by axial tension are analyzed and cohesion formula is obtained. By contrast, the experimental result is consistent with the theoretical analysis. Therefore, the surficial change of anchor colts could influence the performance of the composite anchor bolt. The cohesion force and anchorage performance can be improved by changing the surface of anchor bolts. Research results show that the new composite anchor bolt is high-performance material in the civil engineering.

锚杆张拉力无损测试原理与技术研究

基于锚杆锚固体系多接触面特征,建造室内模型研究其锚固体系振动特性。通过在锚杆无应力段顶端安装加速度传感器测试时程信号,经快速傅里叶变换获得锚杆无应力段顶端振动频谱图,其频谱图的卓越频率具有良好的可识别性,据此获得其卓越频率与锚杆张拉力、锚杆无应力长度的变化规律,其卓越频率并非锚杆张拉段横向多阶振动频率。以此为基础建立了视锚固螺母为弹性基础的锚杆弹性振动模型、锚固螺母及锚杆相对螺母与球形垫圈接触面转动的刚体振动模型,分别获得其模型频率方程,基于其识别的卓越频率求解频率方程中的刚度参数,室内与现场试验表明其刚度参数—锚杆张拉力具有良好的线性相关性和单调递增关系。进一步室内模型试验表明其刚度参数—锚杆张拉力关系特征与蝶形托盘接触不同介质、不同锚杆张拉段长度不具有明显的相关性。为此提出了锚杆张拉力无损测试原理、方法与实现的技术路线,现场小规模试验表明本文提出的方法具有可靠性。

锚栓屈服型可抬升柱脚节点抗震性能试验研究

为满足结构在震中安全且震后可修复使用的目的,设计了一种锚栓屈服型可抬升柱脚节点,该节点是一种半刚性节点,将柱脚锚栓的一部分作为节点的阻尼器,阻尼器为柱脚提供抗弯能力和可抬升能力,在地震时柱脚节点塑性变形主要集中在阻尼器上,震后通过更换阻尼器即可完成柱脚节点的修复。为此,设计一组普通外露式柱脚节点和锚栓屈服型可抬升柱脚节点进行对比试验,并通过拟静力试验,研究它们在低周往复荷载下的滞回特性、抗弯承载力、刚度退化、耗能能力等抗震性能,同时研究柱脚节点在更换阻尼器前后的抗震性能。研究结果表明:对比普通外露式柱脚节点,锚栓屈服型可抬升柱脚具有更好的耗能能力和变形能力,试件的损伤基本集中在可更换的阻尼器上,耗能模式和损伤机制较为合理。在进行修复后,除初期转动刚度略低于修复前试件外,整体抗震性能基本可恢复至震前水平。另外,该新型柱脚的阻尼器拆卸和更换较为简便。

锚杆倒肋式风机基础受力性能的数值模拟

为了解决风机基础施工成本高、施工难度大等问题,提出了一种新型锚杆倒肋式风机基础。利用有限元分析软件ABAQUS对该新型风机基础与传统梁板式风机基础在极端运行荷载工况下的混凝土应力、钢筋应力、基础位移以及基础倾斜率进行数值模拟分析,并进一步讨论二者的混凝土用量、钢筋用量、土方开挖量。结果表明,锚杆的添加以及倒肋的结构设计使锚杆倒肋式风机基础的受力性能、经济性等方面明显优于传统梁板式风机基础,具有较好的应用前景。

风力发电塔基础预应力锚栓T型法兰连接系统计算方法研究

由于锚固区域基础刚度的影响,风力发电塔基础预应力锚栓组件受力不同于塔筒钢管间锻造法兰连接系统。基于Petersen计算方法的原理,推导出适用于预应力锚栓式风力机基础的计算方法,建立包含锚栓组件在内的单区隔和整体有限元模型研究基础约束刚度的空间效应。通过对单区隔和整体有限元计算所得锚栓拉力的对比发现,基础约束刚度的空间效应可忽略不计;通过对整体有限元模型计算结果和工程算法计算结果的对比,验证了工程算法的精度。

既有隧道不同扩挖宽度下锚杆参数的优化

以黄山洞隧道工程为依托,通过对现场数据的监测和利用有限元分析软件Midas GTS NX进行数值模拟,分析了不同扩挖宽度下隧道拱顶沉降值、周边收敛值和围岩有效应力变化的规律,并改变锚杆的长度和锚杆间距,分析在不同锚杆长度下围岩有效应力、衬砌应力以及锚杆应力的变化规律,确定了不同扩挖宽度下最优的锚杆长度和锚杆间距.研究结果表明:随着扩挖宽度的增加,围岩有效应力由大至小依次为拱脚处压应力、拱腰处压应力、拱顶处压应力和仰拱处拉应力;拱顶处压应力随扩挖宽度的增大而减小,拱腰处压应力随扩挖宽度的增大而增大,但增大趋势不明显;受单侧扩挖方式的影响,扩挖侧的应力大于非扩挖侧;拱脚处受到应力集中的影响,其压应力随着扩挖宽度的增大而增大;扩挖宽度为1.5~2.5 m时的最优锚杆长度和间距分别为2.5 m和1.7 m,扩挖宽度为3.5~4.5 m时二者分别为3.0 m和1.2 m.

缓凝型水泥浆液配合比优化及锚孔浆岩界面特性影响研究

针对预应力锚杆后张法施工中自由段浆液流动性和缓凝效果差的工程难题,提出使用标准型聚羧酸减水剂作为掺加剂以实现水泥浆液缓凝并提高其工作性能,探究其对锚孔浆岩界面特性的影响。采用室内试验、SEM电镜扫描等手段,结合Matlab多目标优化等方法,对掺加减水剂的缓凝型水泥浆液的锚固性能及配合比优化展开研究,得出适用于预应力锚杆自由段的注浆材料及其最优配合比,并与现行规范推荐配合比进行锚孔横断面结石特性对比试验。研究结果表明:1)随着水灰比增大,水泥浆液的流动度和凝结时间增大,体积结石率和抗压强度减小;随着减水剂掺量的增大,水泥浆液的流动度和凝结时间增大,体积结石率减小,减水剂对浆液抗压强度影响较小;2)未掺加减水剂时,浆液结石体致密性随着水灰比的增大而降低,掺加减水剂使得浆液结石体表面局部存在相对较大尺度的孔或孔隙,对宏观结石体强度有一定影响;3)通过Matlab多目标优化方法推荐了缓凝型水泥浆液最优配合比为水灰比0.3,减水剂掺量1.85%,相关性能参数符合规范要求,且流动度与抗压强度较规范推荐配合比分别提升了72.3%和107%;4)浸水围岩会弱化浆岩界面的抗剪强度,因此在锚杆灌浆过程中保证横断面结石率有利于提高浆岩界面的抗剪强度,本文提出的最优配合比浆液抗剪强度优于规范推荐配合比浆液。

基于黏聚力模型的螺纹钢锚杆拉拔数值模拟

为研究螺纹钢锚杆锚固结构变形破坏机理,采用ABAQUS软件建立锚固结构轴对称数值模型,基于黏聚力模型,开展数值试验,获得锚固结构拉拔过程中锚杆变形、荷载以及锚固体位移场分布演化规律。试验结果表明:在相同的拉拔位移下,小肋间距锚杆也能够承受更高的拉拔荷载,表明小肋间距锚杆对巷道围岩变形的承载能力更强;在锚杆拉拔过程中,随着拉拔位移的增加,岩体破坏和离层区域呈倒碗形向岩体深部扩散,当拉拔位移增加至9.06 mm后,岩体锚固段末端处位移增速加大,岩体的最大位移为4.79 mm,出现在锚固段端口处,最终导致锚固段基体破坏;锚杆轴力与锚杆肋间距呈负相关,锚杆的轴力随着肋间距的减小而增加。

高延伸率锚索动态力学特性及工程应用

传统锚索延伸率低、抗冲击能力差,在强冲击载荷作用下易出现脆性破断失效,导致巷道出现冒顶、冲击地压事故等问题。基于此,自主开发了具有高强度、高延伸率及高抗冲击等特性的锚索,采用实验室试验、理论分析及现场试验等综合手段,分析了高延伸率锚索的静、动载力学性能,研究了高延伸率锚索化学成分、金相组织和夹杂物与普通锚索的差异,提出了高延伸率锚索支护吸能原理,并将高延伸率锚索在现场进行了应用。研究结果表明:静载作用下,高延伸率锚索抗拉强度为1790 MPa,最大力总延伸率8.1%,是普通锚索的1.61~2.25倍;动载作用下,高延伸率锚索钢丝不易散开,破断载荷与普通锚索基本相同,断后伸长率分别是锚索A、B、C的1.82倍、1.68倍和1.52倍,单位长度吸能量分别是锚索A、B、C的2.54倍、1.99倍和1.70倍,高延伸率锚索塑性变形能力更强,吸能能力更高。高延伸率锚索通过在冶炼和轧制工艺过程中控制有害化学元素和有益化学元素含量、细化金相组织及减少夹杂物尺寸和数量等方式提高了钢丝的塑性变形能力,进而提高锚索整体的抗冲击性能。高延伸率锚索在现场应用过程中经受了多次大能量冲击后,巷道支护效果良好,高延伸率锚索未出现破断,有效控制了巷道冲击破坏。

煤巷钻锚一体化快速掘进技术与装备及应用

分析煤巷掘进技术与装备现状及存在的问题,介绍研发的钻锚一体化快速掘进新模式、新技术、新装备及井下应用效果。研发出钻锚一体化锚杆支护技术与设备,包括钻锚一体化锚杆、泵注式锚固剂、钻锚一体化钻臂、钻箱、锚杆仓、锚固剂泵注系统及智能控制系统,将传统树脂锚固锚杆安装6道工序简化为1道连续工序,实现了锚杆自动化“一键”打设,单根锚杆作业时间由原来5~6 min减少为3 min。研发出自动化喷涂支护技术与装备,包括高强、速凝、抗变形喷涂护表材料,抗拉强度超过9 MPa,断裂伸长率超过100%,黏结强度高于3 MPa;研发出6自由度喷涂系统,可实现随掘自动化快速喷涂作业。研发出巷道随掘变形动态监测技术与系统,实现随掘大粉尘、多干扰、低照度环境下的巷道表面变形监测,监测精度能够满足围岩稳定性评价要求。提出煤巷掘支锚运分区并行协同快速掘进新模式,研制出钻锚一体化快速掘进成套装备。对试验矿井陕西陕煤曹家滩煤矿回采巷道掘进过程中围岩位移和稳定性进行了监测,在时间上,巷道掘出2~3 h后80%以上的围岩位移已经发生;在空间上,距离掘进工作面相当于2倍巷道宽度的位置,90%以上的围岩位移已经完成。快速掘进引起的巷道围岩位移在很短时间内就基本完成,要求支护必须及时且快速。在曹家滩煤矿10 m超大采高综采工作面特大断面回采巷道完成近6000 m的巷道掘进工程,打设钻锚一体化锚杆60000余根。锚杆施工时间、支护用工人数及作业人员劳动强度大幅降低,掘进速度、效率及自动化水平显著提高。试验巷道顶板位移量小、完整稳定,支护效果良好。煤巷钻锚一体化快速掘进技术与装备井下试验取得成功,具备了特大断面煤巷月掘进进尺1500~2000 m的能力。

上拔荷载作用下装配式输电线路岩石群锚基础受力特性研究

为解决传统岩石群锚基础材料耗量大、运输不便的问题,提出一种新型装配式输电线路岩石群锚基础。采用有限元方法建立新型群锚基础的三维精细化数值模型,研究上拔荷载作用下群锚基础受力特性,分析锚杆间距、长度及直径等参数对新型群锚基础锚杆内力的影响规律。结果表明:锚杆内力在钢骨架连接处最大,随深度增加逐渐减小;锚杆距群锚基础形心越远,其内力越大;锚筋长度相同时,随着锚杆间距的增大,锚杆内力呈逐渐变小的趋势,而锚筋长度及直径对内力的变化影响较小。将数值计算结果与规范计算结果进行对比发现:处于与水平荷载方向相反且与群锚中心相距最远的两根锚杆的规范计算结果与数值计算结果吻合度高,其余锚杆两种计算结果的吻合度相对较低。