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Regional 3D geological modeling along metro lines based on stacking ensemble model

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Underground Space 2024年第5期18卷 65-82页

作者： Xia Bian Zhuyi Fan Jiaxing liu xiaozhao li Peng Zhao Key Laboratory of Ministry of Education for Geomechanics and Embankment Engineering Hohai UniversityNanjing 210098China Yunlong Lake Laboratory of Deep Underground Science and Engineering Xuzhou 221000China State Key Laboratory for Geomechanics and Deep Underground Engineering China University of Mining and TechnologyXuzhou 221000China

This paper presents a regional 3D geological modeling method based on the stacking ensemble technique to overcome the challenges of sparse borehole data in large-scale linear underground *** proposed method transforms the 3D geological modeling problem into a stratigraphic property classification problem within a subsurface space grid cell *** data is pre-processed and trained using stacking method with five different machine learning *** resulting modelled regional cells are then classified,forming a regional 3D grid geological model.A case study for an area of 324 km2 along Xuzhou metro lines is presented to demonstrate the effectiveness of the proposed *** study shows an overall prediction accuracy of 85.4%.However,the accuracy for key stratigraphy layers influencing the construction risk,such as karst carve strata,is only 4.3%due to the limited borehole *** address this issue,an oversampling technique based on the synthetic minority oversampling technique(SMOTE)algorithm is *** technique effectively increases the number of sparse stratigraphic samples and significantly improves the prediction accuracy for karst caves to 65.4%.Additionally,this study analyzes the impact of sampling distance on model *** is found that a lower sampling interval results in higher prediction accuracy,but also increases computational resources and time ***,in this study,an optimal sampling distance of 1 m is chosen to balance prediction accuracy and computation ***,the number of geological strata is found to have a negative effect on prediction *** mitigate this,it is recommended to merge less significant stratigraphy layers,reducing computation *** key strata layers,such as karst caves,which have a significant impact on construction risk,further onsite sampling or oversampling using the SMOTE technique is recommended.

关键词： 3D geological modeling Borehole data Stacking Machine learning

A roughness parameter considering joint material properties and peak shear strength model for rock joints

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International Journal of Mining Science and Technology 2021年第3期31卷 413-420页

作者： liren Ban Weisheng Du Tianwei Jin Chengzhi Qi xiaozhao li School of Civil and Transportation Engineering Beijing University of Civil Engineering and ArchitectureBeijing 100044China Deep Mining and Rock Burst Research Institute China Coal Research InstituteBeijing 100013China State Key Laboratory of Coal Mining and Clean Utilization China Coal Research InstituteBeijing 100013China

This study aims at proposing a reasonable roughness parameter that can reflect the peak shear strength(PSS)of rock ***,the contribution of the asperities with different apparent dip angles to shear strength is *** the shear strength of the entire joint asperities is *** results showed that the PSS of the entire joint asperities is proportional to a key parameter hs,which is related to the geometric character of the joint surface and the joint material *** parameter hsis taken as the new roughness parameter,and it is reasonable to associate the PSS with the geometric characteristics of the joint *** on the new roughness parameter and shear test results of 20 sets of joint specimens,a new PSS model for rock joints is *** new model is validated with the artificial joints in this paper and real rock joints in published *** showed that it is suitable for different types of rock joints except for gneiss *** new model has the form of the Mohr-Coulomb model,which can directly reflect the relationship between the 3 D roughness parameters and the peak dilation angle.

关键词： Roughness Joint material properties Rock joints Peak shear strength Asperities

Estimates of strength and cracking behaviors of pre-flawed granite specimens treated by chemical corrosion under triaxial compression tests

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Frontiers of Earth Science 2022年第2期16卷 411-434页

作者： Zhicong li Richeng liU Shuchen li Hongwen JING xiaozhao li liyuan YU State Key Laboratory for Geomechanics and Deep Underground Engineering China University of Mining and TechnologyXuzhou 221116China

Four types of granite specimens were prepared and treated by chemical corrosion for 5 and 30 days,which were then used to carry out triaxial compression tests under different confining pressuresσ_(3).Type A is the intact sample with no preexisting *** B and C are the samples containing two relatively low-dip flaws and two relatively high-dip flaws,*** D is the sample including both relatively low-dip and relatively high-dip *** influences of pH value of chemical solutions,flaw distribution,corrosion time andσ_(3) on triaxial stress-strain curves and ultimate failure modes are analyzed and *** results show that the pH value of the chemical solution,corrosion time and the arrangement of preexisting flaws play crucial roles in the cracking behaviors of granite *** A specimens have the largest peak axial deviatoric stress,followed by Type C,Type D,and Type B specimens,*** is because the decrease in the inclination of preexisting flaws induces the weakening effect due to the decrease in the shadow area along the compaction *** aσ_(3) of 5 MPa,the peak axial deviatoric stress drops by approximately 40.89%,29.08%,4.08%,and 23.53%for pH=2,4,7,and 12,*** intact granite(Type A)specimens,the ultimate failure mode displays a typical shear *** connection of two secondary cracks initiated at the tips of preexisting cracks is always the ultimate failure and crack coalescence mode for Type B *** ultimate failure and crack coalescence mode of Types C and D specimens are significantly affected by pH value of the chemical solution,corrosion time andσ_(3),which is different from those of Types A and B specimens due to the differences in flow distributions.

关键词： granites preexisting flaws chemical corrosion triaxial compression strength cracking behavior

Deformation characteristics and novel strain criteria of strainbursts induced by low-frequency cyclic disturbance

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Deep Underground Science and Engineering 2023年第1期2卷 52-60页

作者： lihua Hu Minghe Ju Peng Zhao xiaozhao li State Key Laboratory for Geomechanics and Deep Underground Engineering China University of Mining and TechnologyXuzhouChina Key Laboratory of Disaster Prevention and Structural Safety of Ministry of Education School of Civil and Architecture EngineeringGuangxi UniversityNanningGuangxiChina

Strainbursts induced by cyclic disturbance with low frequency(termed as cyclicinduced strainbursts)are major dynamic disasters during deep excavation and *** is currently no quantitative criterion available for the prediction of such disastrous *** this study,based on true triaxial experiments,we analyzed the deformation characteristics,established two novel strain criteria for the cyclic-induced strainbursts,and explained the physical meaning of these *** strains for the cyclic-induced strainbursts were defined,including the control strain ε_(ctr),the strain caused by the combined dynamic and static loading ε_(sd),and the ultimate strain ε_(u) after *** indicated by the results,the deformation evolution of the cyclic-induced strainbursts shows remarkable fatigue characteristics,which resemble that of rock subjected to cyclic loading and *** other words,there are three stages during deformation evolution,namely,initial rapid growth,uniform velocity growth after several periods of disturbance,and sudden sharp growth preceding the *** ultimate strain ε_(u) is insensitive to the tangential static stress and disturbance amplitude,but it changes nonlinearly with disturbance *** the perspective of deformation,the occurrence of a cyclic-induced strainburst is controlled by the control strainε_(ctr).Thus,a control strain criterion is proposed;that is,when the stain ε_(sd) is larger than the control strain ε_(ctr),a strainburst will be induced by cyclic ***,based on the statistical results,a strain ratio criterion is proposed;that is,when the strain ratio ε_(sd)/ε_(u) is greater than 30%,a cyclic-induced strainburst will be induced.

关键词： dynamic disturbance low frequency strainbursts strain criteria true triaxial

Fabric changes induced by super-absorbent polymer on cementelime stabilized excavated clayey soil

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Journal of Rock Mechanics and Geotechnical Engineering 2021年第5期13卷 1124-1135页

作者： Xia Bian lingling Zeng xiaozhao li Xiusong Shi Shuming Zhou Fuqing li Key Laboratory of Ministry of Education for Geomechanics and Embankment Engineering Hohai UniversityNanjing210098China College of Civil Engineering and Architecture Zhejiang University of TechnologyHanzhou310014China State Key Laboratory for Geomechanics and Deep Underground Engineering School of Mechanics and Civil EngineeringChina University of Mining and TechnologyXuzhou221116China Beijing Urban Construction Design and Development Group Co. Ltd.Beijing100037China Seazen Holdings Co. Ltd.Shanghai200062China

This paper studies the microstructure variation induced by super-absorbent polymer(SAP)to understand the mechanism of macroscopic strength improvement of stabilized *** fabric changes of cement elime stabilized soil were analyzed with respect to the variation of SAP content,water content,lime content and curing time,using mercury intrusion porosimetry(MIP)*** can be observed that the delimitation pore diameter between inter-and intra-aggregate pores was 0.2 mm for the studied soil,determined through the intrusion/extrusion *** results showed that fabric in both inter-and intra-aggregate pores varied significantly with SAP content,lime content,water content and curing *** main changes in fabric due to SAP are identified as:(1)an increase in intra-aggregate pores(lime cluster space at higher SAP content;and(2)a decrease in inter-aggregate pores represented by a reduction in small-pores(0.2e2 mm)due to the lower pore volume of soil mixture after water absorption by SAP,and a slight increase in large-pores(>2 mm)due to the shrinkage of SAP particle during the freezeedry process of MIP ***,the strength gain due to SAP for cementelime stabilized soil was mainly due to a denser fabric with less interaggregate *** cementitious products gradually developed over time,leading to an increase in intra-aggregate pores with an increasing proportion of micro-pores(0.006e0.2 mm).Meanwhile,the inter-aggregate pores were filled by cementitious products,resulting in a decrease in total void ***,the strength development over time is attributable to the enhancement of cementation bonding and the refinement of fabric due to the increasing cementitious compounds.

关键词： Fabric Soil stabilization Microstructure Super-absorbent polymer(SAP)

Effects of intermediate stress on deep rock strainbursts under true triaxial stresses

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Journal of Rock Mechanics and Geotechnical Engineering 2023年第3期15卷 659-682页

作者： lihua Hu liyuan Yu Minghe Ju xiaozhao li Chun’an Tang State Key Laboratory for Geomechanics and Deep Underground Engineering China University of Mining and TechnologyXuzhou221116China Sate Key Laboratory of Coastal and Offshore Engineering Dalian University of TechnologyDalian116024China Key Laboratory of Disaster Prevention and Structural Safety of Ministry of Education School of Civil and Architecture EngineeringGuangxi UniversityNanning530004China

The effect of intermediate stress(in situ tunnel axial)on a strainburst is studied with a threedimensional(3D)bonded block distinct element method(DEM).A series of simulations of strainbursts under true triaxial in situ stress conditions(*** tangential stress,moderate intermediate stress and low radial stress)of near-boundary rock masses are *** with the experimental results,the DEM model is able to capture the stress-strain response,failure pattern and energy balance of *** fracturing processes of strainbursts are also numerically *** results show that,as the intermediate stress increases:(1)The peak strain of strainbursts increases,the yield stress increases,the rock strength increases linearly,and the ratio of yield stress to rock strength decreases,indicating that the precursory information on strainbursts is enhanced;(2)Tensile and shear cracks increase significantly,and slabbing and bending of rock plates are more pronounced;and(3)The stored elastic strain energy and dissipated energy increase linearly,whereas the kinetic energy of the ejected rock fragments increases approximately exponentially,implying an increase in strainburst *** comparing the experimental and numerical results,the effect of intermediate stress on the rock strength of strainbursts is discussed in order to address three key ***,the Mogi criterion is applied to construct new strength criteria for strainbursts by converting the one-face free true triaxial stress state of a strainburst to its equivalent true triaxial stress *** summary,the effect of intermediate stress on strainbursts is a double-edged sword that can enhance the rock strength and the precursory information of a strainburst,but also increase its intensity.

关键词： Strainbursts Intermediate stress Distinct element method(DEM) Structural failure True triaxial Strength criterion

Quantitative two/three-dimensional spatial characterization and fluid transport prediction of macro/micropores in Gaomiaozi bentonite

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Journal of Rock Mechanics and Geotechnical Engineering 2022年第5期14卷 1568-1579页

作者： Jiangfeng liu Shijia Ma Hongyang Ni Hai Pu xiaozhao li Shaojie Chen State Key Laboratory for Geomechanics and Deep Underground Engineering and School of Mechanics and Civil EngineeringChina University of Mining and TechnologyXuzhou221116China CAEA Innovation Center on Geological Disposal of High Level Radioactive Waste Beijing Research Institute of Uranium GeologyBeijing100029China Key Laboratory of Mining Disaster Prevention and Control Shandong University of Science and TechnologyQingdao266590China

The sealing performance of a bentonite barrier is highly dependent on its seepage characteristics, which are directly related to the characteristics of its pore structure. Based on scanning electron microscopy(SEM) and focused ion beam-SEM(FIB-SEM), the pore structure of bentonite was characterized at different scales. First, a reasonable gray threshold was determined through back analysis, and the image was binarized based on the threshold. In addition, binary images were used to analyze bentonite’s pore structure(porosity and pore size distribution). Furthermore, the effects of different algorithms on the pore structure characterization were evaluated. Then, permeability calculations were performed based on the previous pore structure characteristics and a modified permeability prediction model. For permeability prediction based on the three-dimensional model, the effect of pore tortuosity was also considered. Finally, the accuracy of numerical calculations was verified by conducting macroscopic gas and alcohol permeability experiments. This approach provides a better understanding of the microscale mechanism of gas transport in bentonite and the importance of pore structures at different scales in determining its seepage characteristics.

关键词： Gaomiaozi(GMZ)bentonite Pore structure Permeability prediction Focused ion beam-scanning electron microscopy(FIB-SEM)

Deep sea mineral resources and underground space as well as infrastructure for sustainable and liveable cities

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Deep Underground Science and Engineering 2024年第2期3卷 129-130页

作者： Jianguo Wang Heping Xie Chunfai Leung xiaozhao li School of Mechanics and Civil Engineering China University of Mining and TechnologyXuzhouChina Institute of Deep Earth Sciences and Green Energy Shenzhen UniversityShenzhenChina College of Water Resource and Hydropower Sichuan UniversityChengduChina Center for Offshore Research and Engineering National University of SingaporeSingaporeSingapore State Key Laboratory of Intelligent Construction and Healthy Operation and Maintenance of Deep Underground Engineering China University of Mining and TechnologyXuzhouChina

This issue covers the papers on two special themes:(1)Mineral resources from deep sea—Science and Engineering and(2)Planning and development of underground space and infrastructure for sustainable and liveable cities.

关键词： underground sustainable Deep

Exploring the frontiers of deep underground sciences and engineering—China Yunlong Lake Laboratory is striving to be the best

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Deep Underground Science and Engineering 2022年第2期1卷 131-137页

作者： lihua Hu Jianguo Wang Ali Karrech xiaozhao li Peng Zhao Lulu liu State Key Laboratory for Geomechanics and Deep Underground Engineering China University of Mining and TechnologyXuzhouChina Department of Civil Environmental and Mining EngineeringUniversity of Western AustraliaAustralia

This paper introduces the establishment of deep underground infrastructure for science and engineering ***,the representative deep underground research laboratories and facilities in the world and their functions were summarized and ***,the plan and service target of China Yulong Lake Laboratory were proposed for the storage of resources and energy,as well as the sealing of hazardous waste in deep underground *** this basis,this paper reveals how the facility addresses its key scientific issue on“The law of fluid matter migration in deep underground space”and engineering ***,the construction progress of the facility components was demonstrated in *** is hoped,this paper would provide useful reference to the deep underground research community;meanwhile,international collaboration on deep underground research is highly welcome.

关键词： fluid matter migration large spatial scale long time scale multi-lithology research laboratory and facility underground space