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Experimental study of face passive failure features of a shallow shield tunnel in coastal backfill sand

Frontiers of Structural and Civil Engineering 2024年第2期18卷 252-271页

作者： Weifeng QIAN Ming HUANG Bingnan WANG Chaoshui XU Yanfeng HU School of Civil Engineering Fuzhou UniversityFuzhou 350108China School of Civil Environment and Mining EngineeringUniversity of AdelaideAdelaide 5005Australia china.First Highway Xiamen Engineering Co. Ltd.Xiamen 361000China

Face passive failure can severely damage existing structures and underground utilities during shallow shield tunneling,especially in coastal backfill *** this work,a series of laboratory model tests were developed and conducted to investigate such failure,for tunnels located at burial depth ratios for which C/D=0.5,0.8,1,and *** pressures,the evolution of failure processes,the failure modes,and the distribution of velocity fields were examined through model tests and numerical *** support pressure in the tests first rose rapidly to the elastic limit and then gradually increased to the maximum value in all *** maximum support pressure decreased slightly in cases where C/D=0.8,1,and 1.3,but the rebound was insignificant where C/D=*** addition,the configuration of the failure mode with C/D=0.5 showed a wedge-shaped arch,which was determined by the outcropping shear *** configuration of failure modes was composed of an arch and the inverted trapezoid when C/D=0.8,1,and 1.3,in which the mode was divided into lower and upper failure zones.

关键词： tunnel face stability passive failure model test support pressure failure mode

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Effect of drying-wetting cycles on pore characteristics and mechanical properties of enzyme-induced carbonate precipitation-reinforced sea sand

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Journal of Rock Mechanics and Geotechnical Engineering 2024年第1期16卷 291-302页

作者： Ming Huang Kai Xu Zijian Liu Chaoshui Xu Mingjuan Cui College of Civil Engineering Fuzhou UniversityFuzhou350108China Xiamen Rail Transit Construction and Development Group Co. Ltd.Xiamen361000China School of Civil Environment and Mining EngineeringThe University of AdelaideAdelaide5005Australia

Enzyme-induced carbonate precipitation(EICP)is an emanating,eco-friendly and potentially sound technique that has presented promise in various geotechnical ***,the durability and microscopic characteristics of EICP-treated specimens against the impact of drying-wetting(D-W)cycles is under-explored *** study investigates the evolution of mechanical behavior and pore charac-teristics of EICP-treated sea sand subjected to D-W *** uniaxial compressive strength(UCS)tests,synchrotron radiation micro-computed tomography(micro-CT),and three-dimensional(3D)recon-struction of CT images were performed to study the multiscale evolution characteristics of EICP-reinforced sea sand under the effect of D-W *** potential correlations between microstructure characteristics and macro-mechanical property deterioration were investigated using gray relational analysis(GRA).Results showed that the UCS of EICP-treated specimens decreases by 63.7% after 15 D-W *** proportion of mesopores gradually decreases whereas the proportion of macropores in-creases due to the exfoliated calcium carbonate with increasing number of D-W *** micro-structure in EICP-reinforced sea sand was gradually disintegrated,resulting in increasing pore size and development of pore shape from ellipsoidal to columnar and *** gray relational degree suggested that the weight loss rate and UCS deterioration were attributed to the development of branched pores with a size of 100-1000 m m under the action of D-W ***,the results in this study provide a useful guidancee for the long-term stability and evolution characteristics of EICP-reinforced sea sand under D-W weathering conditions.

关键词： Enzyme-induced carbonate precipitation(EICP) Plant-based urease Drying-wetting(D-W)cycles Microstructure

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Drainage design combining drain holes and pinholes for tunnel boring machine segments subject to high water pressure

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Frontiers of Structural and Civil Engineering 2023年第11期17卷 1723-1738页

作者： Yao LU Ming HUANG Zhijie CHEN Zisheng ZENG Yuchuan LIU Guangzhao DU College of Civil Engineering Fuzhou UniversityFuzhou 350108China Urban Rail Branch China Railway 11th Bureau Group Co.Ltd.Wuhan 430071China

Balance of the groundwater and ecology is crucial for controlled ***,regarding the segments of tunnel boring machines(TBMs)under high water pressure,the stability of the lining structure is often reduced by excessive drain holes required to achieve this *** large discharge of pinholes can easily have severe consequences,such as the lowering of the groundwater table,drying of springs,and vegetation ***,in this study,according to the fluid-structure coupling theory,a new drainage design for TBM segments was developed by considering a mountain tunnel subject to a high water pressure as a case *** evolution characteristics,including the external water pressure of the lining,discharge volume of the segment,and groundwater-table drawdown,were investigated via numerical modeling with drain holes and *** results indicated that the optimal design parameters of drainage segments for the project case were as follows:a circumferential spacing angle and longitudinal number on one side of a single ring of 51°and 2,respectively,for the drain holes and an inclination angle and length of 46.41°and 0.25 times the grouting thickness,respectively,for the pin holes.

关键词： TBM segment high water pressure drain hole pinhole groundwater table drawdown

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Field implementation of enzyme-induced carbonate precipitation technology for reinforcing a bedding layer beneath an underground cable duct

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Journal of Rock Mechanics and Geotechnical Engineering 2023年第4期15卷 1011-1022页

作者： Kai Xu Ming Huang Jiajie Zhen Chaoshui Xu Mingjuan Cui College of Civil Engineering Fuzhou UniversityFuzhou350108China School of Civil Environment and Mining EngineeringUniversity of AdelaideAdelaide5005Australia

A suitable bearing capacity of foundation is critical for the safety of civil *** foundation reinforcement is necessary and an effective and environmentally friendly method would be the preferred *** this study,the potential application of enzyme-induced carbonate precipitation(EICP)was investigated for reinforcing a 0.6 m bedding layer on top of clay to improve the bearing capacity of the foundation underneath an underground cable *** experiments were conducted to determine the optimal operational parameters for the extraction of crude urease liquid and optimal grain size range of sea sands to be used to construct the bedding *** tests were planned based on orthogonal experimental design to study the factors that would significantly affect the biocementation effect on *** dynamic deformation modulus,calcium carbonate content and longterm ground stress variations were used to evaluate the bio-cementation effect and the long-term performance of the EICP-treated bedding *** laboratory test results showed that the optimal duration for the extraction of crude urease liquid is 1 h and the optimal usage of soybean husk powder in urease extraction solution is 100 g/*** calcium carbonate production rate decreases significantly when the concentration of cementation solution exceeds 0.5 mol/*** results of site trial showed that the number of EICP treatments has the most significant impact on the effectiveness of EICP treatment and the highest dynamic deformation modulus(Evd)of EICP-treated bedding layer reached 50.55 *** area with better bio-cementation effect was found to take higher ground stress which validates that the EICP treatment could improve the bearing capacity of foundation by reinforcing the bedding *** field trial described and the analysis introduced in this paper can provide a practical basis for applying EICP technology to the reinforcement of bedding layer in poor ground conditions.

关键词： Enzyme-induced carbonate precipitation (EICP) Plant-based urease Underground cable duct Foundation reinforcement

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