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Mechanical behaviour of fiber-reinforced grout in rock bolt reinforcement

Journal of Rock Mechanics and Geotechnical Engineering 2024年第2期16卷 437-453页

作者： Yingchun Li Ammar Ahmed Danqi Li Deep Underground Engineering Research Center Dalian University of TechnologyDalian116024China WA School of Mines:Minerals Energy and Chemical Engineering Curtin UniversityKalgoorlieWA6430Australia

Grouted rock bolts subject to axial loading in the field exhibit various failure modes,among which the most predominant one is the bolt-grout interface failure.Thus,mechanical characterization of the grout is essential for understanding its performance in ground support.To date,few studies have been conducted to characterize the mechanical behaviour of fiber-reinforced grout(FRG)in rock bolt reinforcement.Here we experimentally studied the mechanical behaviour of FRG under uniaxial compression,indirect tension,and direct shear loading conditions.We also conducted a series of pullout tests of rebar bolt encapsulated with different grouts including conventional cementitious grout and FRG.FRG was developed using 15%silica fume(SF)replacement of cement(by weight)and steel fiber to achieve highstrength and crack-resistance to overcome drawbacks of the conventional grout.Two types of steel fibers including straight and wavy steel fibers were further added to enhance the grout quality.The effect of fiber shape and fiber volume proportion on the grout mechanical properties were examined.Our experimental results showed that the addition of SF and steel fiber by 1.5%fiber volume proportion could lead to the highest compressive,tensile,and shear strengths of the grout.The minimum volume of fiber that could improve the mechanical properties of grout was found at 0.5%.The scanning electron microscopy(SEM)analysis demonstrated that steel fibers act as an excellent bridge to prevent the cracks from propagating at the interfacial region and hence to aid in maintaining the integrity of the cementitious grout.Our laboratory pullout tests further confirmed that FRG could prevent the cylindrical grout annulus from radial crack and hence improve the rebar’s load carrying capacity.Therefore,FRG has a potential to be utilized in civil and mining applications where high-strength and crack-resistance support is required.

关键词： Fiber-reinforced grout(FRG) Steel fibers Mechanical properties Direct shear test pullout test

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Study of bond strength between various grade of Ordinary Portland Cement(OPC)and Portland Pozzolane Cement(PPC)mixes and different diameter of TMT bars by using pullout test

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Frontiers of Structural and Civil Engineering 2013年第1期7卷 39-45页

作者： A D POFALE S P WANJARI Department of Civil Engineering Visvesvarya National Institute of TechnologyNagpur 440010India

Since last two decades,the Portland Pozzolane Cement(PPC)is extensively used in structural concrete.But,till to date,a few literature is available on bond strength of concrete using PPC mixes.There are many literatures available on bond strength of concrete mixes using Ordinary Portland Cement(OPC).Hence,a comparative study was conducted on bond strength between OPC and PPC mixes.In the present investigation,total 24 samples consisting of M20,M35 and M50 grades of concrete and 16 and 25 mm diameter of TMT bar were tested for 7 and 28 days.The pullout bond test was conducted on each specimen as per IS:2770-1967/1997[1]and the results were observed at 0.25 mm slip at loaded end called as critical bond stress and at maximum bond load called as maximum bond stress.It was observed that the critical bond strength of PPC mixes is 10%higher than OPC mixes.Whereas,marginal improvement was noticed in maximum bond strength of PPC mixes.Hence,based on these findings,it could be concluded that development length for PPC mixes could be reduced by 10%as compared with same grade of OPC mixes.

关键词： bond strength Portland Pozzolane Cement(PPC)concrete Ordinary Portland Cement(OPC)concrete bond between concrete and steel pullout test development length

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A novel rock bolting system exploiting steel particles

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International Journal of Mining Science and Technology 2022年第5期32卷 1045-1058页

作者： Xiaowei Feng Fei Xue Valter Carvelli Tongyang Zhao Fengzhen He Dehua Wang State Key Laboratory of Strata Intelligent Control and Green Mining Co-founded by Shandong Province and the Ministry of Science and Technology Shandong University of Science and TechnologyQingdao 266590China School of Mines China University of Mining and TechnologyXuzhou 221116China Key Laboratory of Rock Mechanics and Geohazards of Zhejiang Province College of Civil EngineeringShaoxing UniversityShaoxing 312000China Department A.B.C Politecnico di MilanoMilan 20133Italy

The effectiveness of rock bolting in ground control has been extensively investigated,mainly for resin based systems.Alternative coupling materials are needed to have good mechanical performance and to reduce the economic impact.This study proposed a new bolting system exploiting steel particles as coupling material.The applicability of this system was assessed by laboratory and field pullout tests,assisted by digital imaging correlation(DIC),infrared thermography(IRT)and acoustic emission(AE).The results indicated that,for a 20 mm diameter bolt,the suitable steel particle size and corresponding inner diameter of borehole were 1.4 and 28 mm,respectively.For bolts installed in steel tubes,the particles improved the loading capacity compared to the resin bonded ones.Additional pullout tests on cement blocks indicated that steel particles can be effective for hard rock,whilst resin was a better choice for bolting of soft rock.Similar understanding was obtained by pullout tests in engineering fields,which demonstrated that the steel particles coupled bolts can provide favorable effects in hard rock mass,while the effects were negligible when installed in extremely soft coal mass.The wide set of multi-technique measurements helped to understand the mechanisms involved in the performance of the bolting system with coupling steel particles.

关键词： Rock bolt Steel particle pullout test Digital image correlation Infrared thermography Field test

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Characteristics of root pullout resistance of Caragana korshinskii Kom.in the loess area of northeastern Qinghai-Tibet Plateau,China

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Journal of Arid Land 2022年第7期14卷 811-823页

作者： LIU Yabin SHI Chuan YU Dongmei WANG Shu PANG Jinghao ZHU Haili LI Guorong HU Xiasong Department of Geological Engineering Qinghai UniversityXining 810016China Key Laboratory of Genozoic Resource&Environment in North Margin of the Tibetan Plateau Xining 810016China Key Laboratory of Comprehensive and Highly Efficient Utilization of Salt Lake Resources Qinghai Institute of Salt LakesChinese Academy of SciencesXining 810008China Qinghai Provincial Key Laboratory of Geology and Environment of Salt Lakes Xining 810008China

Roots exert pullout resistance under pullout force,allowing plants to resist uprooting.However,the pullout resistance characteristics of taproot-type shrub species of different ages remain unclear.In this study,in order to improve our knowledge of pullout resistance characteristics of taproot systems of shrub species,we selected the shrub species Caragana korshinskii Kom.in different growth periods as the research plant and conducted in situ root pullout test.The relationships among the maximum pullout resistance,peak root displacement,shrub growth period,and aboveground growth indices(plant height and plant crown breadth)were analyzed,as well as the mechanical process of uprooting.pullout resistance of 4-15 year-old C.korshinskii ranged from 2.49(±0.25)to 14.71(±4.96)kN,and the peak displacement ranged from 11.77(±8.61)to 26.50(±16.09)cm.The maximum pullout resistance and the peak displacement of roots increased as a power function(R^(2)=0.9038)and a linear function(R^(2)=0.8242)with increasing age,respectively.The maximum pullout resistance and the peak displacement increased with increasing plant height;however,this relationship was not significant.The maximum pullout resistance increased exponentially(R^(2)=0.5522)as the crown breadth increased.There was no significant relationship between the peak displacement and crown breadth.The pullout resistance and displacement curve were divided into three stages:the initial nonlinear growth,linear growth,and nonlinear stages.Two modes of failure of a single root occurred when the roots were subjected to vertical loading forces:the synchronous breakage mode and the periderm preferential breakage mode.These findings provide a foundation for further investigation of the soil reinforcement and slope protection mechanisms of this shrub species in the loess area of northeastern Qinghai-Tibet Plateau,China.

关键词： loess area Qinghai-Tibet Plateau pullout resistance growth period aboveground growth indices pullout test Caragana korshinskii

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Effect of embedment length of untreated natural fibres on the bond behaviour in cement mortar

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Frontiers of Structural and Civil Engineering 2018年第4期12卷 454-460页

作者： Gudimella RAMAKRISHNA Sriraman PRIYADHARSHINI Department of Civil Engineering Pondicherry Engineering CollegePuducherry 605014lndia

The present investigation is focused on studying the effects of various matrices with 1:3, 1:4 and 1:5 mortars and fibre types of sisal and coir on the bond behavior at various ages of curing, i.e., 24 h, 3 d, 7 d and 28 d. The other parameters included in the investigation are water/cement (w/c) ratio, sand gradation and embedment length of fibres. In addition, the type of failure of sisal and coir fibres for different mixes of mortars at various curing ages is also reported. From the results, it is seen that the bond strength is improving with respect to age of curing in case of sisal fibres, but decreases in case of coir fibres. The failure of fibres due to fibre fracture is observed in sisal fibres and fibre pullout is observed in coir fibres. The other varying parameters such as mortar mixes, sand gradation, w/c ratio and embedded length also showed significant effect on bond behaviour of sisal and coir fibre with the cement mortar mixes.

关键词： bond strength cement mortar natural fibre pullout test type of failure

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Investigations on pullout behavior of geogrid-granular trench using CANAsand constitutive model

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Journal of Rock Mechanics and Geotechnical Engineering 2017年第4期9卷 726-740页

作者： Ali Noorzad Ehsan Badakhshan Faculty of Civil Water and Environmental Engineering Shahid Beheshti University Tehran Iran

Experimental and numerical investigations have been carried out on behavior of pullout resistance of embedded circular plate with and without geogrid reinforcement layers in stabilized loose and dense sands using a granular trench.Different parameters have been considered,such as the number of geogrid layers,embedment depth ratio,relative density of soil and height ratio of granular trench.Results showed that,without granular trench,the single layer of geogrid was more effective in enhancing the pullout capacity compared to the multilayer of geogrid reinforcement.Also,increasing the soil density and embedment depth ratio led to an increase in the uplift capacity.When soil was improved with the granular trench,the uplift force significantly increased.The granular trench improved the uplift load in dense sand more,as compared to the same symmetrical plate embedded in loose sand.Although it was observed that,in geogrid-reinforced granular trench condition,the ultimate pullout resistance at failure increased as the number of geogrid layers increased up to the third layer,and the fifth layer had a negligible effect in comparison with the third layer of reinforcement.Finite element analyses with hardening soil model for sand and CANAsand constitutive model for granular trench were conducted to investigate the failure mechanism and the associated rupture surfaces utilized.The response of granular material in the proposed model is an elastoplastic constitutive model derived from the CANAsand model,which uses a non-associated flow rule along with the concept of the state boundary surface possessing a critical and a compact state.It was observed that the granular trench might change the failure mechanism from deep plate to shallow plate as the failure surface can extend to the ground surface.The ultimate uplift capacity of anchor and the variation of surface deformation indicated a close agreement between the experiment and numerical model.

关键词： Anchor pullout test Geogrid Granular trench CANAsand constitutive model

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pullout characteristics and conceptual model of gabion reinforcement

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岩石力学与工程学报 2017年第7期36卷 1670-1679页

作者： FANG Wei School offranc and Transportation Engineering Changsha University of Science and TechnologyChangshaHunan 410004China Co-innovation Centerfor Advanced Construction and Maintenance Technology of Modern Transportation Infrastructural Facility Changsha University of Science and TechnologyChangshaHunan 410004China

The reinforced gabion wall on the west line of Xiangtan to Hengyang highway in Hunan province was studied with the large scale pullout model tests and numerical simulations to obtain the interface friction characteristics between the double twisted hexagonal gabion mesh(2.2 mm and 2.7 mm respectively) and red sandstone. The experimental results showed that the pullout displacement-shear stress curve could be roughly divided into 3 sections:the rapid growth,the steady progression and the yielding sections. The thinner gabion mesh led to the higher peak shear stress,larger cohesion and friction angle under the same normal stress. The pullout displacement-shear stress curve from the numerical simulation had two sections,namely,the rapid growth of shear stress and the yielding of gabion mesh. Under the same conditions,the 2.2 mm meshes resulted in the larger drawing coefficient and pseudo-friction coefficient and thus presented the better interface friction properties. The conceptual model suggested that the proportion of pullout force shared by the horizontal bars and longitudinal bars relied on the magnitude,the length,the coefficient of earth pressure and the friction factor,etc. The pullout bearing resistance on the transversal bars(T_1) comprises the largest proportion of the total resistance(about 62%–72%),on the other hand,the proportions of the annular pullout friction on the longitudinal bars(T_2) and the interface friction acting on the surfaces of all nodes(T_3) both grow against T_1 when the normal stress increases.

关键词： numerical simulation gabion mesh pullout test interface friction characteristics conceptual model

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

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Open Journal of Civil Engineering 2016年第2期6卷 217-224页

作者： Jianwei Yue Anquan Xu Tingting Yue Da Song Kai Zheng School of Civil and Architectural Engineering Henan University Kaifeng China

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.

关键词： Composite Anchor Bolt pullout test Surficial Shape Cohesion

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Field Measurements and pullout tests of Reinforced Earth Retaining Wall

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Journal of Southwest Jiaotong University(English Edition) 2004年第2期12卷 165-172页

作者：陈群何昌荣朱分清 Hydraulic and Hydroelectric Engineering College Sichuan University No.2 Survey and Design Institute of Railway Ministry

In this paper, field measurements and pullout tests of a new type of reinforced earth retaining wall, which is reinforced by trapezoid concrete blocks connected by steel bar, are described. Field measurements included settlements of the earth fill, tensile forces in the ties and earth pressures on the facing panels during the construction and at completion. Based on the measurements, the following statements can be made: (1) the tensile forces in the ties increased with the height of backfill above the tie and there is a tensile force crest in most ties; (2) at completion, the measured earth pressures along the wall face were between the values of the active earth pressures and the pressures at rest; (3) larger settlements occurred near the face of the wall where a zone of drainage sand and gravel was not compacted properly and smaller settlements occurred in the well-compacted backfill. The results of field pullout tests indicated that the magnitudes of pullout resistances as well as tensile forces induced in the ties were strongly influenced by the relative displacements between the ties and the backfill, and pullout resistances increased with the height of backfill above the ties and the length of ties.

关键词： Reinforced earth retaining wall Field measurement pullout test

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