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Estimation of hydraulic parameters from pumping tests in a multiaquifer system

Underground Space 2020年第3期5卷 210-222页

作者： Da Ha Gang Zheng Haizuo Zhou Chaofeng Zeng Huihui Zhang School of Civil Engineering Tianjin UniversityTianjin 300072China Key Laboratory of Coast Civil Structure Safety of Ministry of Education Tianjin UniversityTianjin 300072China Hunan Provincial Key Laboratory of Geotechnical Engineering for Stability Control and Health Monitoring School of Civil EngineeringHunan University of Science and TechnologyXiangtanHunan 411201China School of Resources and Environmental Sciences Wuhan UniversityWuhan 430079China

The hydrogeologic conditions in Tianjin,China,are characterized by a system of multiple alternating aquifers and aquitards and a high groundwater ***,the groundwater system to a depth of 70 m includes one phreatic aquifer and three semiconfined aquifers(AqI–AqIII).The distribution of aquifers varies *** estimates of aquifer parameters from pumping tests are essential in geotechnical engineering *** this study,the applicability of different models for estimating hydraulic parameters in a multiaquifer system is *** avoid errors in the graphic-analytical process and to enhance the efficiency and accuracy,a hybrid algorithm,called GALMA(a genetic algorithm(GA)combined with the Levenberg–Marquardt(LM)algorithm),is used with the Neuman and Witherspoon model and ratio *** estimated values in the second and third semiconfined aquifers(AqII and AqIII)from various solutions are compared with the measured *** validations based on the prediction of the drawdown values are performed via a three dimensional numerical simulation.

关键词： Hydraulic parameter Leaky aquifer Pumping test Optimal approach

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Experimental study of one-part geopolymer using different alkali sources

Experimental study of one-part geopolymer using different al...

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2020 International Conference on Internet of Things, Artificial Intelligence and Mechanical Automation, IoTAIMA 2020

作者： Ouyang, Shuntian Chen, Weiquan Zhang, Zongtang Li, Xinming Zhu, Wenfeng Hunan No.6 Engineering Co. Ltd. Changsha410015 China Hunan Prov. Key Laboratory of Geotechnical Engineering for Stability Control and Health Monitoring Hunan University of Science and Technology Xiangtan411201 China School of Resource and Environment and Safety Engineering Hunan University of Science and Technology Xiangtan411201 China

This paper investigates the feasibility of combining different solid alkali materials as activator to prepare one-part geopolymer mortars. The effects of different composite solid activators on aluminosilicate materials were studied and compared with the traditional water glass and sodium hydroxide composite solution activator through the measurement of fresh and harden properties and microstructural analysis. The results showed that sodium metasilicate pentahydrate was more suitable than quick-dissolving sodium silicate for preparation of geopolymer. The addition of sodium carbonate and calcium hydroxide in solid activator enhanced the compressive strength and decreased the setting time and flowability of the mixes. The highest compressive strength (47.4 MPa, 28 d) was obtained with the activators consisting of sodium metasilicate pentahydrate and sodium carbonate. While scanning electron microscope (SEM) analysis indicated that micro-pores left by the dissolution of metasilicate particles might have an adverse effect on the mechanical properties of mortar samples. © 2020 Published under licence by IOP Publishing Ltd.

关键词： Geopolymers

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Hydration mechanism and mechanical properties of slag-phosphogypsum solid waste-based cementitious composite incorporated silica fume

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Construction and Building Materials 2025年 485卷

作者： Ma, Binhui Li, Yuqi Lan, Tian Huang, Bo Chen, Jiasen Peng, Quan Du, Bicheng Ma, Minglei School of Civil Engineering Hunan University of Science and Technology Xiangtan411201 China National Key Laboratory of Green and Long-Life Road Engineering in Extreme Environment Changsha410114 China Hunan Provincial Key Laboratory of Geotechnical Engineering Stability Control and Health Monitoring Xiangtan411201 China Engineering Research Institute China Construction Eighth Engineering Division Corp Ltd Shanghai200000 China Engineering Testing Center Hunan University of Science and Technology Xiangtan411201 China

A new solid waste-based cementitious composite was proposed in this study. Silica fume was incorporated based on the determination of the optimal mixing ratios of granulated blast furnace slag, phosphogypsum and carbide slag to further improve their material properties. Analysis of the strength and material characterization test results revealed that the addition of silica fume led to increased paste viscosity and reduced system alkalinity. These changes hindered the dispersion of precursor particles and decreased the formation of hydration products, collectively resulting in diminished early-age strength of the cured paste system. However, silica fume consumed excess carbide slag, preventing deterioration of hydration products as well as the precipitation and structural alterations of calcium hydroxide crystals, and avoiding the resultant late-stage strength decline. And because the silica fume fills the internal pores while providing additional nucleation sites for the hydration products, the internal structure of the hardened paste became denser, the hydrated gel is tightly connected to the ettringite, and the number of microcracks and harmful pores was significantly reduced, so that it has a higher late-stage strength. The maximum strength of 28d can reach 57.7 MPa. This solid waste-based cementitious composite does not require a chemical activator and high-temperature curing, which can effectively reduce energy consumption and carbon emissions, be conducive to the green development of the construction industry, and promote the recycling of solid waste. © 2025 Elsevier Ltd

关键词： Debris

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Experimental Study on Shear Behavior of Expansive Soil Modified by Gravel Sand 3

Experimental Study on Shear Behavior of Expansive Soil Modif...

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3rd International Conference on Traffic engineering and Transportation System, ICTETS 2019

作者： Yang, Lu Deng, Xiufu Hunan Prov. Key Laboratory of Geotechnical Engineering for Stability Control and Health Monitoring Hunan University of Science and Technology Xiangtan Hunan411201 China School of Civil Engineering Hunan University of Science and Technology Xiangtan Hunan411201 China

Using the strain-controlled direct shear equipment, some direct shear experiments were carried out on the soil samples of Nanyang expansive soil with different gravel ratios under the specific water content, and the shear strength, cohesion and internal friction angle of the expansive soil samples were studied. The experimental results show that the shear strength of the expansive soil samples increases with the increase of vertical pressure. As the proportion of gravel sand increases, the shear strength of expansive soil samples increases to varying degrees. The shear strength of expansive soil increases significantly when the proportion of gravel sand is in the range of 10%∼40%, and the shear strength of remolded soil is the highest when the gravel sand content is 10% under the lower vertical pressure. Under the higher vertical pressure, the shear strength of the remolded soil is the largest when the gravel content is 20%, and the shear strength of expansive soil is close to that of pure expansive soil when the proportion of gravel sand is 50%. The cohesive force of the sample increases first and then decreases sharply with the increase of the proportion of gravel sand, and is maximum when the content of gravel sand is 10%. The internal friction angle increases first and then decreases slowly with the increase of the proportion of gravel sand, and is maximum when the gravel sand content is 40%. The results show that gravel sand can effectively enhance the shear strength index of expansive soil, which can be used as a good engineering application material for improving expansive soil. © Published under licence by IOP Publishing Ltd.

关键词： Shear strength

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Unified theoretical approach to ultimate horizontal pullout capacity of vertical strip anchor plate in sand

Unified theoretical approach to ultimate horizontal pullout ...

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China-Europe Conference on geotechnical engineering, 2016

作者： Hu, Wei Long, Chengbi Gao, Wenhua Zeng, Chaofeng Hunan Province Key Laboratory of Geotechnical Engineering Stability Control and Health Monitoring School of Civil Engineering Hunan University of Science and Technology XiangtanHunan411201 China

ISBN: (纸本)9783319971148

Self-developed visual horizontal drawing strip anchor plate model test and numerical simulation experiment showed that there existed a triangular soil core before anchor plate under ultimate pulling condition, whose two bottom corner’s variation could reflect the symmetry of failure slip-line field indirectly. Along with the increasing of buried ratio, the upper bottom corner enlarged from φ to π/4 + φ/2, and the lower bottom corner reduced from π/2 to π/4 + φ/2 with the sum of two corners basically remained unchanged. In this course, the failure slip-line field before anchor plate evolved from asymmetric to symmetric gradually. Base on this knowledge, corresponding assumptions were put forward to construct the ultimate bearing mechanical model of vertical strip anchor plate under horizontal drawing, and ultimate mechanical equilibrium analysis method was used to derive the unified theoretical formula of ultimate bearing capacity at last. Calculation of four tests and comparison to other two theories indicated that unified theoretical solution had good applicability to vertical strip anchor plate in sand. © Springer Nature Switzerland AG 2018.

关键词： Bearing capacity

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Experimental Study on Shear Behavior of Expansive Soil Modified by Gravel Sand

Experimental Study on Shear Behavior of Expansive Soil Modif...

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作者： Yang Lu Xiufu Deng Hunan Provincial Key Laboratory of Geotechnical Engineering for Stability Control and Health Monitoring Hunan University of Science and Technology School of Civil Engineering Hunan University of Science and Technology

Using the strain-controlled direct shear equipment, some direct shear experiments were carried out on the soil samples of Nanyang expansive soil with different gravel ratios under the specific water content, and the shear strength, cohesion and internal friction angle of the expansive soil samples were studied. The experimental results show that the shear strength of the expansive soil samples increases with the increase of vertical pressure. As the proportion of gravel sand increases, the shear strength of expansive soil samples increases to varying degrees. The shear strength of expansive soil increases significantly when the proportion of gravel sand is in the range of 10%～40%, and the shear strength of remolded soil is the highest when the gravel sand content is 10% under the lower vertical pressure. Under the higher vertical pressure, the shear strength of the remolded soil is the largest when the gravel content is 20%, and the shear strength of expansive soil is close to that of pure expansive soil when the proportion of gravel sand is 50%. The cohesive force of the sample increases first and then decreases sharply with the increase of the proportion of gravel sand, and is maximum when the content of gravel sand is 10%. The internal friction angle increases first and then decreases slowly with the increase of the proportion of gravel sand, and is maximum when the gravel sand content is 40%. The results show that gravel sand can effectively enhance the shear strength index of expansive soil, which can be used as a good engineering application material for improving expansive soil.

关键词： Experimental Study on Shear Behavior of Expansive Soil Modified by Gravel Sand

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A New C++ Programming Strategy for Three-Dimensional Sphere Discontinuous Deformation Analysis

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International Journal of Geomechanics 2020年第10期20卷

作者： Huang, Gang-Hai Xu, Yuan-Zhen Chen, Xiao-Feng Xia, Ming Zhang, Shu Yi, Xiong-Wei Hunan Prov. Key Laboratory of Geotechnical Engineering for Stability Control and Health Monitoring School of Civil Engineering Hunan Univ. of Science and Technology Xiangtan411201 China College of Civil Engineering and Mechanics Xiangtan Univ. Xiangtan411105 China School of Resources and Safety Engineering Central South Univ. Changsha410082 China School of Resource and Environment and Safety Engineering Hunan Univ. of Science and Technology Xiangtan411201 China

A new C++ programming strategy with high modularization and good portability, and a novel data storage format for simultaneous equations with little computer memory consumption, no sorting operation, and simple addressing algorithm are proposed for the three-dimensional sphere discontinuous deformation analysis (3D SDDA) to overcome the shortcomings of existing computation programs. An object-oriented data structure for the 3D SDDA computing code that is highly modular and easily transplanted is designed. Then, to demonstrate the portability of the 3D SDDA computing code, two computation architectures are respectively constructed to form two independent computation programs for 3D SDDA. Finally, several benchmark tests are conducted to verify the correctness of the 3D SDDA model in the new computation program, and a 170,725-sphere landslide example is simulated on a desktop computer to demonstrate the capability of the new computation program in large-scale engineering applications. Comparison between the new and existing computation programs regarding computer memory and time consumed demonstrates the great advantages brought about by the new computation program. © 2020 American Society of Civil Engineers.

关键词： C++ (programming language)

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Effect of geomembrane defects on the degradable contaminant transport through composite geomembrane cutoff walls: A novel transient model

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Journal of Environmental Chemical engineering 2025年第5期13卷

作者： Chun-Hui Peng Xiang-Hong Ding Hong-Xin Chen Yong He Biao Luo School of Architecture and Civil Engineering Jinggangshan University Key Laboratory of Jiangxi Province for Agricultural Environmental Pollution Prevention and Control in red Soil Hilly Region Ji’an 343009 China School of Civil Engineering Central South University Changsha 410075 China Department of Geotechnical Engineering Tongji University Shanghai 200092 China Key Laboratory of Metallogenic Prediction of Nonferrous Metals and Geological Environment Monitoring Central South University Ministry of Education Changsha 410083 China School of Civil Engineering Hunan University Changsha 410082 China

Composite geomembrane cutoff walls (CGCW) are among the most effective techniques for managing contaminated sites. Accurately predicting contaminant transport through CGCW is essential to the efficient remediation and management of contaminated sites. Previous prediction models have predominantly focused on contaminant diffusion in intact CGCW, with insufficient attention given to CGCW with geomembrane (GMB) defects. This study introduces fully transient models for contaminant transport in a CGCW-aquifer system, comprising an upstream slurry wall, a GMB with defects, a downstream slurry wall, and the adjacent aquifers. The model allows for three types of GMB defects, i.e., joint defects, bottom gaps, and GMB holes, and incorporates the contaminant advection-diffusion-adsorption-degradation process in the CGCW-aquifer system. Results indicate that existing CGCW models overlook the critical impact of GMB positioning on the containment performance of CGCW with GMB defects. The semi-infinite boundary assumption and the non-degradation assumption commonly adopted in previous models lead to, respectively, an underestimation and overestimation of contaminant plume concentrations in the downstream aquifer. Additionally, increasing the widths of joint defects, bottom gaps, and GMB holes significantly reduces the containment efficiency of CGCW, especially under conditions of high hydraulic head and low slurry wall permeability. To address this, an equivalent design curve for CGCW with GMB defects is proposed, offering engineers a practical reference for determining the required wall thickness.

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Responses of retaining wall to pre-excavation dewatering under staggered layout of dewatering wells

Responses of retaining wall to pre-excavation dewatering und...

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China-Europe Conference on geotechnical engineering, 2016

作者： Zeng, Chao-Feng Yuan, Zhi-Cheng Xue, Xiu-Li Hu, Wei Hunan Provincial Key Laboratory of Geotechnical Engineering for Stability Control and Health Monitoring School of Civil Engineering Hunan University of Science and Technology XiangtanHunan411201 China

ISBN: (纸本)9783319971148

Pre-excavation dewatering (PED) is an important stage in deep excavation in soft ground with high groundwater level. The PED-induced deformations of retaining wall and surrounding environment can reach centimeter level. However, the method to control this deformation has not been yet proposed by the traditional pit design theory and relevant research. In this paper, a countermeasure, which is called as staggered layout of dewatering well, is proposed. In this method, it is recommended that deeper wells and smaller spacings of neighboring wells are employed near the retaining wall. The numerical results show that this method can effectively limit the PED-induced wall deflection. © Springer Nature Switzerland AG 2018.

关键词： Finite element method

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Distribution patterns of horizontal foundation modulus under pre-excavation dewatering

Distribution patterns of horizontal foundation modulus under...

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China-Europe Conference on geotechnical engineering, 2016

作者： Xue, Xiu-Li Li, Miao-Kun Zeng, Chao-Feng Hunan Provincial Key Laboratory of Geotechnical Engineering for Stability Control and Health Monitoring School of Civil Engineering Hunan University of Science and Technology XiangtanHunan411201 China

ISBN: (纸本)9783319971148

Pre-excavation dewatering (PED) can cause a significant wall deflection. How to predict this deformation is an urgent problem to be solved. The elastic foundation beam method is widely adopted to predict the wall deflection. A key issue that need to be addressed in the use of this method is to obtain the distribution of the horizontal foundation modulus. However, the distribution pattern of horizontal foundation modulus under PED is not clear. In this study, a numerical model is established and verified, and a series of numerical simulations are carried out to investigate the distribution of horizontal foundation modulus along depth under conditions of different excavation width and depth. The numerical results are compared with those computed by the ‘m method’, which is a traditional excavation design method recommended in the Chinese Code. The results indicate that under the common conditions of PED, the horizontal foundation modulus decreases greatly compared with the values determined by m method, and the larger the excavation width and dewatering depth, the greater the decrease extent. When using the elastic foundation beam method to predict the PED-induced wall deflection, the deflection will be underestimated if the m method is used to determine the horizontal foundation modulus. © Springer Nature Switzerland AG 2018.

关键词： Excavation

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