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 0.5m, 0.8m, 1.0m, diameter of 10mm, 15mm, 20mm, setting spacing of 3.0m, 2.5m, 2.0m, 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 2.53.5m, the diameter is 2535mm, the spacing is 0.50.6m, and the setting angle is 105°.

Hydrogeochemical modelling of corrosive environment contributing to premature failure of anchor bolts in underground coal mines

Anchor bolts are commonly used throughout underground mining and tunnelling operations to improve roof stability.However,premature failures of anchor bolts are significant safety risks in underground excavations around the world due to susceptible bolt materials,a moist and corrosive environment and tensile stress.In this paper,laboratory experiments and hydrogeochemical models were combined to investigate anchor bolt corrosion and failure associated with aqueous environments in underground coal mines.Experimental data and collated mine water chemistry data were used to simulate bolt corrosion reactions with groundwater and rock materials with the PHREEQC code.A series of models quantified reactions involving iron and carbon under aerobic and anaerobic conditions in comparison with ion,pH and pE trends in experimental data.The models showed that corrosion processes are inhibited by some natural environmental factors,because dissolved oxygen would cause more iron from the bolts to oxidize into solution.These interdisciplinary insights into corrosion failure of underground anchor bolts confirm that environmental factors are important contributors to stress corrosion cracking.

Prediction of a maximum pull-out load of anchor bolts using an optimal combination model

The mixed model of improved exponential and power function and unequal interval gray GM(1,1)model have poor accuracy in predicting the maximum pull-out load of anchor bolts.An optimal combination model was derived using the optimally weighted combination theory and the minimum sum of logarithmic squared errors as the objective function.Two typical anchor bolt pull-out engineering cases were selected to compare the performance of the proposed model with those of existing ones.Results showed that the optimal combination model was suitable not only for the slow P-s curve but also for the steep P-s curve.Its accuracy and stable reliability,as well as its prediction capability classification,were better than those of the other prediction models.Therefore,the optimal combination model is an effective processing method for predicting the maximum pull-out load of anchor bolts according to measured data.

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.

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.

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.

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.

基于螺栓预紧力监测土工离心机不平衡力的方法研究

研究了一种基于监测地脚螺栓轴向预紧力变化的土工离心机动态不平衡力在线测量方法。首先,通过理论推导了不同的不平衡力状态下,地脚螺栓的轴向预紧力变化模型,证明了间接测试离心机不平衡力的可行性。其次,在TLJ-500型离心机上开展试验,获得了动态不平衡力矩随配重变化的规律,并对测点轴向力变化进行拟合,建立了测点轴向力与不平衡质量及离心机运行重力加速度g值的关系。最后,对一个地脚螺栓的预紧力变化进行测量,通过响应面拟合可建立地脚螺栓轴向预紧力的变化与离心机运行加速度和配重质量的关联。研究表明,通过监测地脚螺栓预紧力变化获得的离心机运行不平衡力的方法具有一定可行性,试验中应保持不同配重的质心一致;根据拟合式计算使转臂平衡的配重质量时,应尽量采用较大的加速度以降低离心机未甩平带来的误差。

隧道预应力树脂中空注浆锚杆施工技术应用研究

预应力树脂中空注浆锚杆施工技术是一种较为先进的工法,集锚固和注浆于一体,与传统锚杆施工工艺相比,具有施工速度快、锚固性能好、操作简单等特点。为了有效保障隧道工程施工安全和质量,文章以永兴隧道为例,研究了预应力树脂中空注浆锚杆在加固项目中的有效应用,介绍了预应力树脂中空注浆锚杆结构与加固原理,阐述了中空注浆锚杆的施工流程及施工质量措施,以供参考。

高速公路路基高边坡稳定性及加固方案

针对太原西北二环高速公路K18+620右侧高边坡出现的滑移现象及地质不稳定问题,通过现场勘查和地质调查,分析了高边坡岩体结构特征和边坡变形的主要诱发因素,利用简化Bishop法,进行了边坡稳定性计算和评估,计算结果表明,在天然、地震及有水工况下,边坡均存在不同程度的滑移风险,采用“锚杆+坡面格构”相结合的防护设计方案,结合排水系统设置和植被修复等综合防护措施,以提高边坡的抗滑能力及稳定性。

BIM技术在深基坑设计中的应用研究

以北京某深基坑工程为例,介绍了其基坑支护设计方案,探讨了BIM技术在基坑支护设计中的应用,具体分为通过Revit软件建立基坑支护模型和利用Navisworks进行碰撞检查分析,以检验设计方案中可能出现的问题并做出适当的设计调整。

回采巷过断层围岩支护方案设计

断层地质对巷道围岩稳定性构成严重威胁,易引发顶板垮塌、变形及突发性涌水等安全事故。文章以煤矿Ⅱ3采区Ⅱ1135机巷为例,其受断层影响,巷道出现顶板冒落、肩角剪切及高帮滑移等现象。通过模拟和计算,设计了一套针对性的断层区域支护方案。模拟分析表明,该支护方案可改善巷道应力环境,顶板下沉量和两帮移近量分别减少51.4%和33.3%,围岩塑性区深度也大幅减小,从而有效增强了巷道的稳定性。

煤矿两臂锚杆机器人钻臂控制系统开发

针对煤矿用两臂锚杆机器人锚杆钻臂控制系统存在控制精度低、实时性不高等问题,提出基于PWM控制、变频控制以及CAN总线通讯技术融合的锚杆钻臂控制系统设计方案,以CX5020-1122为核心控制器,采用模糊PID控制方法对电动机运行速度进行精确控制,采用PWM控制方法对电磁阀开度进行实时控制;采用CAN总线通讯技术与锚杆钻臂的操作面板、HMI人机界面以及变频器完成控制指令与状态数据交互。通过试验和实际应用分析表明,设计的锚杆钻臂控制系统成孔施工孔距误差≤90 mm,孔径误差≤5 mm,孔深误差≤50 mm;最高支护数为182根/班且一次完成,减少锚杆支护工3人/班,安全性好;满足煤矿井下锚杆支护工程应用要求。

大采高综采面软岩回采巷道围岩控制技术应用

大运华盛煤业20203工作面采用一次采全高综合机械化采煤工艺,运输顺槽顶底板均为软岩、巷道断面较大,围岩控制困难。围绕大采高软岩回采巷道的变形特点及支护方法展开分析,提出及时支护与动压影响软岩巷道补强支护的围岩控制技术方案。现场应用后,顶板下沉量、两帮移近量和底鼓量最大值分别较优化前减少了43.8%、71.0%和59.0%,巷道围岩变形基本稳定。

Testing and modeling of cyclically loaded rock anchors

The Norwegian Public Roads Administration(NPRA) is planning for an upgrade of the E39 highway route at the westcoast of Norway. Fixed links shall replace ferries at seven fjord crossings. Wide spans and large depths at the crossings combined with challenging subsea topography and environmental loads call for an extension of existing practice. A variety of bridge concepts are evaluated in the feasibility study. The structures will experience significant loads from deadweight, traffic and environment. Anchoring of these forces is thus one of the challenges met in the project. Large-size subsea rock anchors are considered a viable alternative. These can be used for anchoring of floating structures but also with the purpose of increasing capacity of fixed structures. This paper presents first a thorough study of factors affecting rock anchor bond capacity. Laboratory testing of rock anchors subjected to cyclic loading is thereafter presented. Finally, the paper presents a model predicting the capacity of a rock anchor segment, in terms of a ribbed bar, subjected to a cyclic load history. The research assumes a failure mode occurring in the interface between the rock anchor and the surrounding grout. The constitutive behavior of the bonding interface is investigated for anchors subjected to cyclic one-way tensile loads. The model utilizes the static bond capacity curve as a basis, defining the ultimate bond sbuand the slip s1 at τ. A limited number of input parameters are required to apply the model. The model defines the bond-slip behavior with the belonging rock anchor capacity depending on the cyclic load level(τcy/τ), the cyclic load ratio(R= τcy/τcy), and the number of load cycles(N). The constitutive model is intended to model short anchor lengths representing an incremental length of a complete rock anchor.

Test and application of hydraulic expansion bolts in a roadway under goaf with ultra-close separation

The roof of a roadway under goal with ultra-close separation consists of thin rock strata and rocks caving in upper goal. Influenced by the mining of the upper coal seam, the roof is loose and broken, and its integ- rity is poor. Resin anchored bolts cannot provide an effective anchoring force in such roof conditions. By conducting free expansion tests and field pull-out tests on a hydraulic expansion bolt, this study has ana- lyzed the influencing factors and laws of radial expansion and anchoring force changes in the rod body. This has revealed the anchoring mechanism of such bolts, and has obtained reasonable water injection pressures and suitable drilling diameters （which are 20-25 MPa and 32-35 mm respectively） for the hydraulic expansion bolt （cR28 mm） used in these tests. Based on pull-out tests at different interlayer spacing, the applicability of hydraulic expansion bolts had been verified for controlling the roof of road- ways under goal with ultra-close distance. Combined with the deformation and failure characteristics of the test roadway roof, this paper proposes a united roof-control technology based on the use of hydraulic expansion bolts and advancing intubation for the roof. Engineering practice indicated that the roof of the test roadway did not generate leaking and caving phenomenon, and the amount of roof deformation was controlled to within 150 mm. Maintenance of the roadway roof has been improved significantly, which ensures safe mining in coal seams with ultra-close separation.

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。