Simulation of dilatancy-controlled gas migration processes in saturated bentonite using a coupled multiphase flow and elastoplastic H2 M model

Dilatancy-controlled gas flow in preferential pathways plays a key role in the safety analysis of radioactive waste repositories.This is particularly the case for bentonite,an often-preferred barrier material.Gas flow in preferential pathways is characterized by localization and spontaneous behavior,which is challenging to simulate in numerical models due to strong hydro-mechanical coupling.To analyze a laboratory experiment in the framework of the DECOVALEX-2023 project,this study introduced a new approach of combining continuous modelling methods with spatial material properties derived from material heterogeneities and experimental observations.The proposed model utilized hydro-mechanical spatial distributions,namely Young’s modulus and gas entry pressure,and elastoplasticity combined with a linear swelling model.A conceptual strain-dependent permeability approach simulated dilatancycontrolled gas flow based on hydro-mechanical coupling.To test the effectiveness of the presented approach,a gas injection test in a compacted,saturated bentonite sample was simulated using the opensource code OpenGeoSys 5.8 and compared with experimental observations.The presented methodology is capable of simulating localized gas flow in preferential pathways.The spatial distributions of Young’s modulus and gas entry pressure affect the swelling pressure,relative permeability and,in combination with the strain-dependent permeability model,also the intrinsic permeability.

A Simplified Method for the Stress Analysis of Underground Transfer Structures Crossing Multiple Subway Tunnels

According to the design specifications,the construction of extended piles involves traversing the tunnel’s upper region and extending to the underlying rock layer.To address this challenge,a subterranean transfer structure spanning multiple subway tunnels was proposed.Deliberating on the function of piles in the transfer structure as springs with axial and bending stiffness,and taking into account the force balance and deformation coordination conditions of beams and plates within the transfer structure,we established a simplified mechanical model that incorporates soil stratification by combining it with the Winkler elastic foundation beam model.The resolved established simplifiedmechanicalmodel employed finite difference technology and the Newton-Simpsonmethod,elucidating the mechanical mechanism of the transfer structure.The research findings suggest that the load carried by the upper structural columns can be transferred to the pile foundation beneath the beams through the transfer structure,subsequently reaching the deep soil layer and ensuring minimal impact on adjacent tunnels.The established simplified analysis method can be used for stress analysis of the transfer structure,concurrently considering soil stratification,pile foundation behavior,and plate action.The pile length,pile section size,and beam section size within the transfer structure should account for the characteristics of the upper load,ensuring an even distribution of the beam bending moment.

Thermal and Mechanical Characterization of Compressed Clay Bricks Reinforced by Rice Husks for Optimizing Building in Sahelian Zone

This article deals with the characterization of local materials used in insulation building heat. These materials are bricks of earth compressed and stabilized with rice husks. Thermal conductivity, the specific heat and the thermal diffusivity of materials based on clay incorporating rate of 0, 2%, 4%, 6%, 8% and 10% are determined. The results showed that the clay blocks + rice balls had better thermal insulators than simple clay blocks. However, these composite materials used for the envelope of the building must have sufficient mechanical resistance when used in construction. The measurement of mechanical properties such as compressive strength showed an improvement of 6% and beyond, a drop in resistance when increasing rice husks in clay is observed. These results allow to specify the optimal conditions of use of these materials for the building envelope.

Investigation of the Effect of the Force Arm on the Bending Capability of Prestressed Glulam Beam

Prestress enables the Glulam beam could make full use of the compression strength,and then increase the span,but it still could not reduce all drawbacks,such as cross-section weakening and small force arm.To avoid slotting and ensure suitable tension and compression couple,one kind of novel anchor has been proposed,which could meet the bearing capacity requirement.And then the bending test of prestressed Glulam beams with a geometric scale ratio of 1:2 was simulated,to investigate the effect of the force arm on bending capacities,failure modes,and deformation performance.Results show that increasing the force arm could improve the ultimate bending per-formance of the beam significantly,and the anchor arm length has a certain effect on the performance,but it is not obvious.Finally,based on Finite element method analysis,the practice design suggestions have been offered.

Research on seismic behavior and shear strength of SRHC frame columns

The seismic behavior of steel reinforced high strength and high performance concrete （SRHC） frame columns was investigated through pseudo-static experiments of 16 frame columns with various shear span ratios, axial compression ratios, concrete strengths, steel ratios and stirrup ratios. Three kinds of failure mechanisms are presented and the characteristics of experimental hysteretic curves and skeleton curves with different design parameters are discussed. The columns＇ ductility and energy dissipation were quantitatively evaluated based on seismic resistance. The research results indicate that SRHC frame columns can withstand extreme bearing capacity, but the abilities of ductility and energy dissipation are inferior because of SRHC＇s natural brittleness. As a result, the axial load ratio should be restricted and some construction measures adopted, such as increasing the stirrup ratio. This research established effect factors on the bearing capacity of SPHC columns. Finally, an algorithm for obtaining ultimate bearing capacity using the flexural failure mode is established based on a modified plane- section assumption. The authors also established equations to determine shearing baroclinic failure and shear bond failure based on the accumulation of the axial load force distribution ratio. The calculated results of shear bearing capacity for different failure modes were in good agreement with the experimental results.

A Model for Regional Energy Utilization by Offline Heat Transport System and Distributed Energy Systems—Case Study in a Smart Community, Japan

Under the Kyoto Protocol,Japanwas supposed to reduce six percent of the green house gas (GHG) emission in 2012. However, until the year 2010, the statistics suggested that the GHG emission increased 4.2%. What is more challenge is, afterFukushimacrisis, without the nuclear energy,Japanmay produce about 15 percent more GHG emissions than1990 inthis fiscal year. It still has to struggle to meet the target set by Kyoto Protocol. The demonstration area of “smart community” suggests Japanese exploration for new low carbon strategies. The study proposed a demand side response energy system, a dynamic tree-like hierarchical model for smart community. The model not only conveyed the concept of smart grid, but also built up a smart heat energy supply chain by offline heat transport system. Further, this model promoted a collaborative energy utilization mode between the industrial sector and the civil sector. In addition, the research chose the smart community inKitakyushuas case study and executed the model. The simulation and the analysis of the model not only evaluate the environmental effect of different technologies but also suggest that the smart community inJapanhas the potential but not easy to achieve the target, cut down 50% of the CO2 emission.

Geophysical Study: Estimation of Deposit Depth Using Gravimetric Data and Euler Method (Jalalabad Iron Mine, Kerman Province of IRAN)

Mineral exploration is done by different methods. Geophysical and geochemical studies are two powerful tools in this field. In integrated studies, the results of each study are used to determine the location of the drilling boreholes. The purpose of this study is to use field geophysics to calculate the depth of mineral reserve. The study area is located 38 km from Zarand city called Jalalabad iron mine. In this study, gravimetric data were measured and mineral depth was calculated using the Euler method. 1314 readings have been performed in this area. The rocks of the region include volcanic and sedimentary. The source of the mineralization in the area is hydrothermal processes. After gravity measuring in the region, the data were corrected, then various methods such as anomalous map remaining in levels one and two, upward expansion, first and second-degree vertical derivatives, analytical method, and analytical signal were drawn, and finally, the depth of the deposit was estimated by Euler method. As a result, the depth of the mineral deposit was calculated to be between 20 and 30 meters on average.

Influence of the Colorless Waste Glass on the Mineralogical, Microstructural and Mechanical Properties of Clay Material from Wack (Adamawa, Cameroon)

This study reports the investigation of the influence of adding waste glass on the properties of fired clay specimen. Four different particle sizes (smaller than 100 μm, 300μm, 500μm, and 800 μm) of waste glass were mixed with a clay material at contents of 0%, 2%, 6% and 10% per weight. Specimen samples were fired at 750℃ in an electrical furnace for 6 hours, at a heating rate of 5℃/min. The physical and mechanical properties of terracotta are studied. The chemical analysis revealed that the clays were dominated by kaolinite and montmorillonite with small proportion of mixed layers clay. The fine grained texture (0.002 mm > 25%) and high plasticity (WP > 30%) of the clays were responsible for the moderate and high values of shrinkage upon oven drying and firing. The firing color variation from reddish brown shade was due to the amounts of iron and titanium oxides present in the obtained material. The water absorption was varied between 17.40% and 13.70%, while the linear shrinkage was estimated to be between 0.70% and 1.20% and the flexural strength from 5.30 to 8.10 MPa. These results showed that mixing clay with waste glass at 750℃ is an interesting approach to obtain reddish brown ceramics destined for bricks or roofing tiles.

Urban and architectural sustainable design strategies:Case of Chongqing

Sustainable design strategies for Chongqing City,China,are presented. The analysis is made on the local climate context,since it is quite essential for sustainable building design. An emphasis is put on passive design,considering both urban and building scales. Other issues of relevance are also discussed,such as the potential for the use of renewable energy systems. The analysis of a case study,a typical detached house,newly built,is also shown.

Electronic Structure and Thermoelectric Power Factor of Na_xCoO_2 from First-Principles Calculation

To investigate the relationship between the electronic structure and the power factor of Nax CoO2 （x = 0.3, 0.5 and 1.0）, the first-principles calculation is conducted by using density functional theory and the semi-classical Boltzmann theory. Our results suggest that with the decreasing Na content, a transition from semiconductor to semimetal is observed. Na0.3CoO2 possesses a higher electrical conductivity at 1000 K due to its increased density of states near the Fermi energy level. However, an optimal Seebeck coefficient at 1000 K is obtained in Na0.5CoO2 because of its broadened band gap near the Fermi energy level Consequently, a maximum power factor is realized in Na0.5CoO2. Thus our work provides a complete understanding of the relationship between the electronic structure and the thermoelectric power factor of Nax CoO5.

Stress Analysis of New Type Pre-Stressed Anchor Bearing Plate Combining Stamping with Welding Forming and Its Anchorage Zone

An anchor bearing plate transfers the anchoring force from anchor plate to the concrete and the pre-stress is formed in the concrete structure. Currently, the main type of anchor bearing plate is cast iron. It is brittle during transportation and tension process. This paper presents a new type of anchor bearing plate combined stamping with welding forming. The structure of the new type anchor bearing plate is introduced. The stress states of the anchor bearing plate and anchorage zone under work are studied. Various specifications of anchor bearing plate are studied by ANSYS finite element analysis software following the AASHTO specification. The analysis results are compared with the results of the same type of OVM round-shaped anchor plate. The study results show that the new pre-stressed anchor plates combined stamping with welding forming are feasible and more sturdy which can meet the engineering demand.

Synthesis and Low Thermal Characterization of Local Soil Based-Building Adobe

This work studies the mechanical properties of the soil cement brick and soil cement brick mixed with fly ash from the east of Thailand, Rayong province. The purpose is to develop the new low cost materials used in the local area of Thailand. Results show that the average of the compressive strength and the modulus of rupture (MOR) of soil cement brick mixed with Eastern Rayong fly ash are lower than those of non-fly ash soil cement brick. Also both properties values increase with increasing cured time. However, the thermal conductivity shows the decreasing trend with increasing fly ash content. By conclusion, considered by mechanical properties show that soil cement brick mixed with an Eastern Rayong fly ash can efficiently produce as the structural clay load- bearing tile.

Structural Condition and Deficiencies of Present Constructed Bridges over Zahirshahi Canal and Proposal of New Design Using AASHTO Codes

This paper addresses a comprehensive design of RCC T-beam Bridge based on AASHTO design standards. The bridge is designed and proposed to be constructed over an irrigation canal (Zahirshahi canal) of Kandahar province, Afghanistan that has more than 30 bridges over it. Yet they are not enough, and the demand for construction of new bridges is gradually arising because of the vast urbanization in the surrounding of the canal. Most of the bridges on this canal are Reinforced Concrete Slab (RCS) bridges;?these type bridges are limited by capacity and are generally found only in smaller spans. Since they can only span short distances and are often constructed as multiple-span?bridges with vertical supports between the abutments to allow a longer length.?All constructed slab bridges over Zahirshahi canal are four-span bridges. Constructing multi-span bridges on the canal decreases waterway due to the existence of many piers and footings that could increase the water level during the peak flow, even, sometimes can cause over flow. Taking into consideration these deficiencies of the present (RCS) bridges, two-span RCC T-beam Bridge is one of the best alternatives to be constructed over the canal. In addition, canal cross-sectional dimensions are almost constant along its length, though the construction of two-span RCC T-beam bridge is applicable at any point of the canal. The design is selected based on exclusive survey of the area during all seasons including the peak flowing of the canal.

Serviceability Analysis of Non-Prismatic Timber Beams: Derivation and Validation of New and Effective Straightforward Formulas

This paper provides innovative and effective instruments for the simplified analysis of serviceability limit states for pitched, kinked, and tapered GLT beams. Specifically, formulas for the evaluation of maximal horizontal and vertical displacements are derived from a recently-proposed Timoshenko-like non-prismatic beam model. Thereafter, the paper compares the proposed serviceability analysis formulas with other ones available in literature and with highly-refined 2D FE simulations in order to demonstrate the effectiveness of the proposed instruments. The proposed formulas lead to estimations that lie mainly on the conservative side and the errors are smaller than 10% (exceptionally up to 15%) in almost all of the cases of interest for practitioners. Conversely, the accuracy of the proposed formulas decreases for thick and highly-tapered beams since the beam model behind the proposed formulas cannot tackle local effects (like stress concentrations occurring at bearing and beam apex) that significantly influence the beam behavior for such geometries. Finally, the proposed formulas are more accurate than the ones available in literature since the latter ones often provide non-conservative estimations and errors greater than 20% (up to 120%).

Assessment of the Influence of Sulfuric Acid/Hydrogen Peroxide Mixture on Organic Sulfur Reduction of High Sulfur Coals and Their Chemical Composition

One of the contaminants in coal is sulphur. The adverse impact of sulfur on coal, such as environmental pollution, degradation of steel quality, and reduction of coal’s thermal value, has led to the attention of sulfur separation methods in recent decades. Leaching (chemical dissolution) is one of the best methods for desulfurising coal, reducing sulfur in coal. In this study, hydrogen peroxide as an oxidising agent on sulfuric acid yield in reducing sulfur types of coal and chemical structure and the organic texture of high sulfur coal was investigated. The experiments were designed using a three-level response surface methodology with four duplicate points and 27 experiments. The independent variables studied were temperature, time, stirring speed and ratio of sulfuric acid to hydrogen peroxide. Dependent variables included reduction percentage of total, pyritic and organic sulfur. This study showed that 99.99% of total sulfur, 30.11% of pyritic sulfur and 69.08% of organic sulfur were reduced. These values were obtained at a temperature of 60°C, time 120 min, stirring speed 200 rpm and 3:1 ratio of sulfuric acid to hydrogen peroxide. Significant changes were observed by infrared spectroscopy (FTIR) of the coal structure before and after desulphurisation. On the other hand, the studies showed no specific changes in the bonds related to the organic coal matrix. The results showed that this method could be used as a secure process for removing inorganic and organic sulfur without destroying the organic coal matrix.