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THE reinforcing mechanism OF TiB2 IN TiB2/A357 COMPOSITE

Acta Metallurgica Sinica(English Letters) 2003年第5期16卷 375-378页

作者： B.Yu Y.J.Zhang Z.X.Zhao~ F.X.Zhao: Q.K.Cai C.S.Liu ShenyangResearchInstituteofFoundry TheChineseAcademyofMachinerySciencesShenyang110022China EastChinaUniversityofScienceandTechnology Shanghai200237China SchoolofMaterials&Metallurgy NortheasternUniversityShenyang110004China

Mechanical properties were tested for in situ TiB2/A357 composite fabricated by LSM (mixed salts reaction) method. Micro structures of as cast and plastic deformed TiB2/A357 were investigated. The results show that there is a low misfit between (200) Al and (101)TiB2 with [011]//Al [101]TiB2. There is a change from fully dendritic structure of the α-Al of A357 to a rosette-type structure of TiB2/A357. Significant increases in proof stress and Young's modulus can be obtained at low TiB2 additions. There exist dislocation loops around neighboring TiB2 particles with about 0.1μm in diameter and dislocation multiplication near TiB2 particles.

关键词： TiB2/Al in situ composite reinforcing mechanism

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Investigation of the failure mechanism and theoretical model of bolt-reinforced shallow tunnel faces with different bolt lengths

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Underground Space 2024年第3期16卷 126-142页

作者： Xiao Zhang Li Yu Mingnian Wang Henghong Yang Ming Lu Zexing Li Langzhou Tang School of Civil Engineering Southwest Jiaotong UniversityChengdu 610036SichuanChina Key Laboratory of Traffic Tunnel Engineering Ministry of EducationSouthwest Jiaotong UniversityChengdu 610036SichuanChina School of Transportation and Logistics Southwest Jiaotong UniversityChengdu 610036SichuanChina

Using fiberglass bolts to reinforce a tunnel face is a practical auxiliary technology for ensuring tunnel face stability in soft *** reinforcing effect and the economics of this technology are significantly affected by bolt ***,to date,the failure mechanism of bolt-reinforced tunnel faces with different bolt lengths has rarely been *** reveal the failure mechanism of bolt-reinforced shallow tunnel faces,in this study,the stability of bolt-reinforced tunnel faces with different bolt lengths was investigated by using laboratory tests and numerical simulations,and a simplified theoretical model for practical engineering was *** face support pressure and failure pattern for different bolt lengths during the face collapse process were obtained,and the influence of bolt length on face stability was clearly *** specifically,the results show that face stability increases with increasing bolt length,and the reinforcing effect of face bolts is governed by the shear failure at the soil-grout interface first in the stable zone of the tunnel face and then in the failure *** the bolt length in the stable zone is larger than that in the failure zone,face stability will not be improved with increasing bolt length;thus,this bolt length is referred to as the optimal bolt length L_(opt).The L_(opt)value is slightly larger than the initial failure range(in the unreinforced condition)and can be approximately calculated by L_(opt)=(1-0.0133u)D(u is the friction angle of the soil,and D is the tunnel diameter)in practical ***,a simplified theoretical model was established to analyse the stability of reinforced tunnel faces,and the results are in good agreement with both laboratory tests and numerical *** proposed model can be used as an efficient tool for the design of face bolts.

关键词： Failure mechanism Face bolting Tunnel face stability Bolt length reinforcing mechanism

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