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Cross-scale characteristics of backfill material using NMR and fractal theory

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Transactions of Nonferrous Metals Society of China 2020年第5期30卷 1347-1363页

作者： Jian-hua HU Qi-fan REN Dong-jie YANG Shao-wei MA Jun-long SHANG Xiao-tian DING Zhou-quan LUO School of Resources and Safety Engineering Central South UniversityChangsha 410083China School of Civil and Environmental Engineering Nanyang Technological University50 Nanyang AvenueSingapore

This paper analyzed the pore structure, quantified the pore fractal dimension, calculated the grading index(GI) of mixed aggregate, and studied the relationship among GI, pore structure, and strength to describe the cross-scale characteristics of backfill, which is made from stone powder and cemented tailing. A series of experiments were conducted on stone powder cement tailings backfill(SPCTB). The GI formulas for mixed aggregates, containing stone powder and tailings, were derived based on the Füller theory. The nuclear magnetic resonance(NMR) fractal dimensions of backfills were derived using fractal geometry principles. Compared to the mesopore and macropore fractal dimensions, the correlation between micropore fractal dimension and macro-properties in terms of NMR porosity, pore structure complexity, uniaxial compression strength(UCS), and GI is the most significant. Macropore fractal dimension is generally correlated with UCS and GI and the other properties such as the shape of mixed aggregates also have an impact on fractal dimension. However, mesopore fractal dimension has no obvious relationship with macro-properties. Finally, the relationship between GI and UCS was studied, which contributed to improving backfill’s strength and optimizing gradation.

关键词： backfill material cross-scale characteristics grading index fractal dimension nuclear magnetic resonance

Realizing of Optimization of Binder backfill material Under Certain Strength with Fuzzy Sets

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Journal of China University of Mining and Technology 2001年第2期11卷 147-149页

作者：崔明义胡华 Department of Resource Exploitation Engineering CUMT Beijing 100083 P.R.China

The main factors deciding the compressive strength of binder backfill body are tailing density and binder dosage in binder backfill materials. Based on the antecedent of certain pulp density, the method of increasing the tailing density and reducing the binder dosage, or the manner of cutting down the tailing density and gaining the binder dosage are taken to guarantee the strength of backfill body. The problem that should be solved is how to determine the tailing density and the binder dosage rationally. This paper tries to realize the correct selection of the tailing density and the binder dosage in computer with the method of fuzzy mathematics.

关键词： tailing density binder dosage fuzzy sets backfill material compressive strength

Coupled hydro-mechanical analysis of expansive soils:Parametric identification and calibration

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Journal of Rock Mechanics and Geotechnical Engineering 2020年第3期12卷 620-629页

作者： Abhishek Rawat Linzhi Lang Wiebke Baille Anne-Catherine Dieudonne Frederic Collin Department of Foundation Engineering Soil and Rock MechanicsRuhr-Universität BochumUniversitätsstraße 15044780BochumGermany Faculty of Civil Engineering and Geosciences Delft University of TechnologyBuilding 232628 CN Delftthe Netherlands ArGEnCo University of Liege4000 LiegeBelgium

A methodology for identifying and calibrating the material parameters for a coupled hydro-mechanical problem is presented in this pape *** validation purpose,a laboratory-based water infiltration test was numerically simulated using finite element method(FEM).The test was conducted using a self-designed column-type experimental device,which mimicked the wetting process of a candidate backfill material in a nuclear waste *** real-time measurements of key state variables(*** content,relative humidity,temperature,and total stresses)were performed with the monitoring sensors along the height of cylindrical soil *** numerical simulation,the modified Barcelona Basic Model(BBM)along with soil-water retention model for compacted bentonite was *** shows that the identified model parameters successfully captured the moisture migration process under an applied hydraulic gradient in a bentonite-based compacted soil sample.A comparison between the measured and predicted values of total stresses both in axial and lateral directions along with other state variables revealed that heterogeneous moisture content was distributed along the hydration-path,resulting in non-uniform stress-deformation characteristics of soil.

关键词： Compacted bentonite backfill material Deep geological repository Constitutive modeling Hydro-mechanical coupling Water infiltration test

Thermal Response Test by Improved Test Rig with Heating or Cooling Soil

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Transactions of Tianjin University 2014年第1期20卷 15-20页

作者：付文成朱家玲张伟 Key Laboratory of Efficient Utilization of Low and Medium Grade Energy of Ministry of Education Tianjin University Tianjin Geothermal Research and Training Center Tianjin University

An improved test rig providing both the heat and cold source was used to perform thermal response test （TRT）, and the line source model was used for data analysis. The principle of determining the temperature difference between the inlet and outlet of test well can keep the heating or cooling rate constant, along with a reduced size of test rig. Among the influencial factors of the line source model, the temperature difference was determined as the most important, which agreed with the test results. When the gravel was taken as the backfill material, the soil thermal conductivities of heating and cooling at the test place were 1.883 W/（m＆#183;K） and 1.754 W/（m＆#183;K）, respectively, and the deviation of TRT between heating and cooling soil was 6.8%. In the case of fine sand, the thermal conductivities of heating and cooling were 1.541 W/（m＆#183;K） and 1.486 W/（m＆#183;K）, respectively, and the corresponding deviation was 6%. It was also concluded that different velocities of water had less influence on TRT than the temperature difference.

关键词： ground source heat pump thermal response test thermal conductivity backfill material

Recovery of Mining Wastes in Building materials: A Review

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Open Journal of Civil Engineering 2021年第4期11卷 379-397页

作者： Alinabiwe Nyamuhanga Ally Manjia Marcelline Blanche Ursula Joyce Pettang Nana Masika Muhiwa Grâce Ngapgue François Chrispin Pettang Laboratory Engineering Civil and Mechanics Doctoral Research Unit for Engineering and Applications University of Yaoundé I Yaoundé Cameroon Department of Civil Engineering Faculty of Applied Sciences and Technologies Free University of Great Lakes Countries Goma DRC Department of Civil Engineering National Advanced School of Engineering of Yaoundé University of Yaoundé I Yaoundé Cameroon Department of Civil Engineering Fotso Victor University Institute of Technology University of Dschang Bandjoun Cameroon

The use of materials from waste in buildings compensates for the lack of natural resources, solves the problem of waste management and provides an alternative technique for protection of the environment. There are a large number of industrial wastes that are used for full or partial replacement of raw materials in some construction materials. This review assesses mining waste in concrete as a substitute for aggregates and cement;in fired bricks as a substitute for soil;and in road backfill as a substitute for soil. This paper reviews some mining tailings, mine waste rocks and some slags obtained in the exploitation and/or processing of some ores including iron, gold, lead, phosphate, copper, coal, etc. Different physical properties, mechanical properties, chemical properties, heavy metal content, mineralogic composition, geotechnical properties and environmental properties (leaching test) of the mine wastes were examined. The physical, mechanical and environmental properties of the materials obtained by substitution of raw materials by mine waste were examined and compared to reference materials. Mining waste in cementitious materials offers good compressive strengths, while the porosity of the concrete and/or mortar is a factor influencing its toxicity. As for the waste in fired bricks, fired at a temperature of 900°C or more, it offers convincing compressive and flexural strengths. The few research studies obtained on the use of mining waste in road embankments have shown that mining waste can be used as a sub-base layer and backfill as long as it is not toxic. In addition, several other mining wastes require special attention as substitutes for raw materials in construction materials, such as coltan, cobalt.

关键词： Mining Waste Tailings Waste Rock Slug Fired Brick backfill material Cement materials