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Mechanical behavior of EICP-treated calcareous sands under high confining pressures

Journal of Rock Mechanics and geotechnical engineering 2025年第3期17卷 1816-1827页

作者： Qian Zhang Weimin Ye Wei Su Qiong Wang Yonggui Chen Department of Geotechnical Engineering College of Civil EngineeringTongji UniversityShanghai200092China Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education Tongji UniversityShanghai200092China

Calcareous sands are widely distributed on the coral reefs,continental shelf,and seashores between 30north and south latitude and are commonly utilized as filling materials for the construction of artificial islands and infrastructure *** this study,calcareous sands were cemented by enzymatically induced carbonate precipitation(EICP)*** triaxial tests were conducted on the EICPtreated calcareous *** showed that the specimens with different cementation levels exhibited different responses in mechanical *** differences in the sand fabric after consolidation under a relatively high confining pressure resulted in the untreated specimen exhibiting a higher peak strength compared to the lightly cemented *** confining pressures exhibited a strongly inhibiting effect on dilatancy,which could be counteracted by increasing the cementation *** EICP-treated specimen could have one or two yield points(smaller-strain and larger-strain yields).For lightly cemented specimens,the smaller-strain yield stress decreased under high confining pressures due to the partial carbonate bonding degradation during *** stress line of untreated particle breakage(UPB)was a critical boundary to distinguish failure mode in the p′-q *** the EICP-treated specimens,the yield stress located above or below the UPB stress line indicates the simultaneous or sequential breakage of the carbonate bonds and sand particles,***,the EICPtreated specimen exhibited brittle or ductile *** mode transformation could be triggered by increasing cementation level or confining pressure.

关键词： EICP technique Calcareous sand Bonding degradation Yield strength Failure mechanism

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Thermal effects on the strain rate-dependent behavior of highly compacted GMZ01 bentonite

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Journal of Rock Mechanics and geotechnical engineering 2025年第1期17卷 453-464页

作者： Pengju Qin Weimin Ye Qiong Wang Yonggui Chen College of Civil Engineering Taiyuan University of TechnologyTaiyuan030024China Department of Geotechnical Engineering College of Civil EngineeringTongji UniversityShanghai200092China Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education Tongji UniversityShanghai200092China

Investigation of thermal effects on the strain rate-dependent properties of compacted bentonite is crucial for the long-term safety assessment of deep geological repository for disposal of high-level radioactive *** the present work,cylindrical GMZ01 bentonite specimens were compacted with suction-controlled by the vapor equilibrium ***,a series of temperature-and suction-controlled stepwise constant rate of strain(CRS)tests was performed and the rate-dependent compressibility behavior of the highly compacted GMZ01 bentonite was *** plastic compressibility parameterλ,the elastic compressibility parameterκ,the yield stress p0,as well as the viscous parameterαwere *** indicate thatλ,κandαdecrease and p0 increases as suction *** heating,parametersλ,αand p0 *** is also found that p0 increases linearly with increasing CRS in a double-logarithm *** on the experimental results,a viscosity parameterα(s,T)was fitted to capture the effects of suction s and temperature T on the relationship between yield stress and strain ***,an elastic-thermo-viscoplastic model for unsaturated soils was developed to describe the thermal effects on the rate-dependent behavior of highly compacted GMZ01 *** showed that the calculated results agreed well to the measured ones.

关键词： Highly compacted bentonite Rate-dependent behavior Constant rate of strain Temperature Elastic-thermo-viscoplastic model

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A review of test methods for uniaxial compressive strength of rocks:Theory,apparatus and data processing

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Journal of Rock Mechanics and geotechnical engineering 2025年第3期17卷 1889-1905页

作者： Wei-Qiang Xie Xiao-Li Liu Xiao-Ping Zhang Quan-Sheng Liu En-ZhiWang State Key Laboratory of Hydroscience and Engineering Tsinghua UniversityBeijing100084China Yunlong Lake Laboratory of Deep Underground Science and Engineering Xuzhou221000China The Key Laboratory of Safety for Geotechnical and Structural Engineering of Hubei Province School of Civil EngineeringWuhan UniversityWuhan430072China

The uniaxial compressive strength(UCS)of rocks is a vital geomechanical parameter widely used for rock mass classification,stability analysis,and engineering design in rock *** UCS testing methods and apparatuses have been proposed over the past few *** objective of the present study is to summarize the status and development in theories,test apparatuses,data processing of the existing testing methods for UCS *** starts with elaborating the theories of these test *** the test apparatus and development trends for UCS measurement are summarized,followed by a discussion on rock specimens for test apparatus,and data processing ***,the method selection for UCS measurement is *** reveals that the rock failure mechanism in the UCS testing methods can be divided into compression-shear,compression-tension,composite failure mode,and no obvious failure *** trends of these apparatuses are towards automation,digitization,precision,and multi-modal *** size correction methods are commonly *** is to develop empirical correlation between the measured indices and the specimen *** other is to use a standard specimen to calculate the size correction *** to five input parameters are commonly utilized in soft computation models to predict the UCS of *** selection of the test methods for the UCS measurement can be carried out according to the testing scenario and the specimen *** engineers can gain a comprehensive understanding of the UCS testing methods and its potential developments in various rock engineering endeavors.

关键词： Uniaxial compressive strength(UCS) UCS testing methods Test apparatus Data processing

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Fracture behavior of sandstone with partial filling flaw under mixed-mode loading: Three-point bending tests and discrete element method

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Journal of Rock Mechanics and geotechnical engineering 2025年第1期17卷 291-308页

作者： Dongdong Ma Yu Wu Xiao Ma Xunjian Hu Wenbao Dong Decheng Li Lingyu Li State Key Laboratory for Geomechanics and Deep Underground Engineering China University of Mining and TechnologyXuzhou221116China State Key Laboratory of Structural Health and Safety of Bridges Wuhan430034China Research Center of Coastal and Urban Geotechnical Engineering Zhejiang UniversityHangzhou310058China State Key Laboratory of Geomechanics and Geotechnical Engineering Institute of Rock and Soil MechanicsChinese Academy of SciencesWuhan430071China

The fracture behavior of natural fracture in the geological reservoir subjected to filling property,affects the crack initiation and propagation under stress *** filling flaws were intermediate between open fractures and filled fractures,the fracture response may be worth *** this work,the effect of the filling property of sandstone with partial filling flaws on the fracture behavior was systematically investigated based on three-point bending tests and the numerical approach of discrete element method(DEM).In the laboratory,semi-circular three-point bending tests were carried out with partial filling flaws of various filling *** on this,numerical simulations were used to further investigate the effect of the filling ratio and the inclination of the partial filling flaw on the mechanical and fracture responses,and the effect of the partial filling flaw under mixed-mode loading on the fracture mechanism was elucidated coupled with acoustic emission(AE)*** obtained results showed that the increase in filling strength and filling ratio of partial filling flaw led to an increase in peak strength,with a decreasing trend in peak strength with the inclination of partial filling *** terms of crack propagation pattern,the increasing filling strength of the partial filling flaw induced the transformation of the fracture mechanism toward deflection,with a tortuosity path,while the filling ratio and inclination of partial filling flaw led to fracture mechanism change from deflection to penetration and attraction,accompanied with a larger AE event source in ***,the b-value based on the Gutenberg-Richter equation fluctuated between 5 and 4 at low filling ratio and inclination and remained around 5 at high filling ratio and inclination of partial filling *** results may provide an application prospective for reservoir stimulation using the natural fracture system.

关键词： Partial filling flaw Mixed-mode loading Semi-circular three-point bending Acoustic emission(AE) b-value

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Thermal Effect on the Breakdown Pressure of Granite in Supercritical CO2 Fracturing: Experimental Study and Model Validation

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SPE Journal 2025年第4期30卷 1740-1755页

作者： Liu, Shuyuan Zhu, Wancheng Liu, Heyang Wei, Chenhui Zhang, Xiufeng Liu, Zhengdong Center for Rock Instability and Seismicity Research Department of Mining Engineering School of Resource and Civil Engineering Northeastern University Shenyang China Tongji University Key Laboratory of Geotechnical and Underground Engineering Ministry of Education Shanghai China

Breakdown pressure (Pb) is a key parameter in supercritical carbon dioxide (SC-CO2) fracturing technology. A limited understanding of the thermal effects resulting from the difference between SC-CO2 and reservoir temperatures impedes accurate Pb prediction. In our work, fracturing experiments were conducted on granite to analyze the impacts of temperature and injection rate in terms of the thermal effects on Pb. Additionally, we establish an effective Pb prediction model that considers thermal effects, achieving a low error rate relative to the experimental data. As the temperature increases from 308 to 328 and 348 K, the experimental Pb decreases by 8.34% and 20.35%, respectively. The rising temperature reduces the viscosity and pressurization rate of SC-CO2, thereby increasing the stress caused by the infiltration effect, which is inversely related to Pb. As the temperature difference increases from 0 to 20 and 60 K, the experimental Pb decreases by 3.27% and 13.19%, respectively. The thermal stress induced by these temperature differences negatively impacts Pb, and increases in temperature difference enhance thermal stress and weaken the pore pressure at the characteristic length dw. As the injection rate increases from 30 to 50 and 70 mL/min, the experimental Pb increases by 4.84% and 18.38%, respectively. The weakened infiltration effect and reduced thermal stress at dw increase the Pb under faster injection rates. Increased temperature differences and lower injection rates significantly reduce the breakdown pressure of low-permeability rocks due to combined thermal stress and fluid infiltration but have relatively minor effects on high-permeability rocks. Copyright © 2025 Society of Petroleum Engineers.

关键词： Granite

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Fatigue properties and constitutive model of Jintan salt rock subjected to complex cyclic loading

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International Journal of Mining Science and Technology 2025年第1期35卷 121-133页

作者： Qingchuan He Jianfeng Liu Fei Wu Cunbao Li Jie Chen Renbo Gao Chunfeng Ye Shijie Zhu State Key Laboratory of Coal Mine Disaster Dynamics and Control Chongqing UniversityChongqing 400044China State Key Laboratory of Hydraulics and Mountain River Engineering Sichuan UniversityChengdu 610065China State Key Laboratory of Intelligent Construction and Healthy Operation and Maintenance of Deep Underground Engineering College of Civil and Transportation EngineeringShenzhen UniversityShenzhen 518060China State Key Laboratory of Geomechanics and Geotechnical Engineering Institute of Rock and Soil MechanicsChinese Academy of SciencesWuhan 430071China

Salt cavern energy storage technology contributes to energy reserves and renewable energy *** study focuses on salt cavern gas storage in Jintan to assess the long-term stability of its surrounding rock under frequent *** fatigue test results indicate that stress holding significantly reduces fatigue life,with the magnitude of stress level outweighing the duration of holding time in determining peak *** a machine learning approach,the impact of various factors on fatigue life and peak strain was quantified,revealing that higher stress limits and stress holding adversely impact the fatigue index,whereas lower stress limits and rate exhibit a positive effect.A novel fatigue-creep composite damage constitutive model is constructed,which is able to consider stress magnitude,rate,and stress *** model,validated through multi-path tests,accurately captures the elasto-viscous behavior of salt rock during loading,unloading,and stress *** analysis further reveals the time-and stress-dependent behavior of model parameters,clarifying that strain changes stem not only from stress variations but are also influenced by alterations in elasto-viscous *** study provides a new method for the mechanical assessment of salt cavern gas storage surrounding rocks.

关键词： Salt cavern gas storage Cyclic loading Fatigue characteristics Constitutive model

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Experimental and numerical studies on propagation behavior between hydraulic fractures and pre-existing fractures under prepulse combined hydraulic fracturing

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Journal of Rock Mechanics and geotechnical engineering 2025年第5期17卷 2879-2892页

作者： Wei, Chao Yu, Liyuan Geng, Shentao Yuan, Zichen Wang, Yubo State Key Laboratory of Intelligent Construction and Healthy Operation and Maintenance of Deep Underground Engineering China University of Mining and Technology Xuzhou 221116 China Institute of Geotechnical and Underground Engineering Shandong University Jinan 250061 China

Prepulse combined hydraulic fracturing facilitates the development of fracture networks by integrating prepulse hydraulic loading with conventional hydraulic fracturing. The formation mechanisms of fracture networks between hydraulic and pre-existing fractures under different prepulse loading parameters remain unclear. This research investigates the impact of prepulse loading parameters, including the prepulse loading number ratio (C), prepulse loading stress ratio (S), and prepulse loading frequency (f), on the formation of fracture networks between hydraulic and pre-existing fractures, using both experimental and numerical methods. The results suggest that low prepulse loading stress ratios and high prepulse loading number ratios are advantageous loading modes. Multiple hydraulic fractures are generated in the specimen under the advantageous loading modes, facilitating the development of a complex fracture network. Fatigue damage occurs in the specimen at the prepulse loading stage. The high water pressure at the secondary conventional hydraulic fracturing promotes the growth of hydraulic fractures along the damage zones. This allows the hydraulic fractures to propagate deeply and interact with pre-existing fractures. Under advantageous loading conditions, multiple hydraulic fractures can extend to pre-existing fractures, and these hydraulic fractures penetrate or propagate along pre-existing fractures. Especially when the approach angle is large, the damage range in the specimen during the pre-pulse loading stage increases, resulting in the formation of more hydraulic fractures. © 2025 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences

关键词： Fracture networks Fracture propagation Pre-existing fracture Prepulse combined hydraulic fracturing Prepulse loading parameters

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A modified state parameter for identifying flow liquefaction in aeolian sand

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Geotechnique Letters 2025年第2期15卷 1-9页

作者： Xu, Wendong Li, Xuefeng Zeng, Sheng Tang, Zhenghui Lü, Xilin Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education Department of Geotechnical Engineering Tongji University Shanghai China School of Civil and Hydraulic Engineering Ningxia University Yinchuan China Department of Civil Engineering University of British Columbia VancouverBC Canada Guangxi Communications Design Group Co. Ltd Guangxi Nanning530029 China

Static liquefaction is when sandy soils lose shear strength and deform rapidly under undrained shearing. This phenomenon has three undrained responses: flow, limited flow, and nonflow (not liquefied). Among them, flow is the most dangerous, marked by complete strength loss and significant deformation. Thus, recognizing flow liquefaction is crucial in interpreting liquefaction behaviors. Aeolian sand which has low fine content, non-cohesion, and poor size distribution, was found to be highly liquefiable, and so was used to explore the liquefaction characteristics via undrained triaxial tests with different initial stresses and void ratios. The experimental results showed an obvious effect of stress on the flow behavior of liquefaction in aeolian sand. A modified state parameter corrected by critical mean effective stress and void ratio was introduced to consider the stress effect. It was proved to identify the flow behavior on aeolian sand successfully, based on the value of the modified state parameter. A state-dependent hardening plasticity model, incorporating the modified state parameter, was introduced. This model effectively simulates undrained triaxial tests on aeolian sand, accurately capturing all behavior types: flow, limited flow, and nonflow responses. © 2025 Emerald Publishing Limited: All rights reserved.

关键词： Soil liquefaction

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A spatiotemporal data mining method for advanced prediction and assessment of large combined excavation-induced wall deformations and risks

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Journal of Rock Mechanics and geotechnical engineering 2025年第5期17卷 2758-2777页

作者： Tang, Linhong Liao, Shaoming Yang, Yifeng Fan, Yaoyao Liu, Zhi Department of Geotechnical Engineering College of Civil Engineering Tongji University Shanghai 200092 China Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education Tongji University Shanghai 200092 China China Construction Eighth Engineering Division Corp. Ltd. Shanghai 200120 China

A holistic and precise assessment of retaining wall deformations is critical for on-site risk management of large combined deep excavation projects, where the risk-related points are highly dispersed, evolving, and interacting. Despite extensive exploration of this topic in previous studies, the omission of intricate spatiotemporal characteristics of wall deformations has resulted in diminished prediction accuracy and stability. To mitigate this deficiency, a spatiotemporal characteristics matrix for all data points and time series was first generated for a deep excavation scenario and used as input for a new hybrid model that combines convolutional neural network (CNN) and long short-term memory (LSTM) with incorporated attention mechanism (CNN-LSTM-Att), which enables the cross-learning mechanism and improves interpretability. In addition, by leveraging the attention weight, a new risk assessment index for retaining wall deformations across various scenarios was formulated. Then the proposed method was applied in a large combined deep excavation in Shanghai, China. The results show that: (1) The incorporation of fed-in characteristic data and the attention mechanism enables the proposed method to produce satisfactory prediction results for the holistic spatiotemporal distribution of a large combined excavation;(2) Compared with other published models, the proposed model shows much better prediction accuracy, interpretability, and stability, especially in medium- and long-term predictions;and (3) The new risk assessment index serves as a reliable decision-making tool for assessing the risk evolution of retaining wall deformations and provides valuable guidance for effective risk management in multi-scenario excavation projects. © 2025 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences

关键词： Attention mechanism Deformation risk Large combined deep excavation Spatiotemporal characteristics matrix

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Diagnosing building moisture conditions using CNN analysis of infrared and microwave signatures 2

Diagnosing building moisture conditions using CNN analysis o...

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2nd International Academic Conference on Optics and Photonics, IACOP 2024

作者： Wang, Fuzhi Fang, Maoliu Huang, Jizhong Lu, Yuan Department of Geotechnical Engineering College of Civil Engineering Tongji University Shanghai200092 China Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education Tongji University Shanghai200092 China Department of Civil Engineering Shanghai University Shanghai200444 China

ISBN: (数字)9781510688827

ISBN: (纸本)9781510688810

Water is a significant cause of cultural heritage deterioration, making moisture detection crucial for heritage conservation. This study utilizes infrared thermography (IRT) in combination with microwave technology to quantitatively and qualitatively assess moisture distribution and dampness-related deterioration in China's Yungang Grottoes. The method accurately diagnoses moisture content and distribution by using a Convolutional Neural Network (CNN) for multi-feature image fusion. Non-destructive techniques and statistical analyses, such as signal-to-noise ratio (SNR) and spatial stability, improve the detection of moisture damage. Statistical analysis confirmed the accuracy of IRT and microwave technology for qualitative and quantitative moisture assessment, providing valuable support for conservation and management strategies. © 2025 SPIE.

关键词： Nondestructive examination

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