Reduce Construction Costs Research Articles

The Influence of Structural Design on the Hydrodynamics of Floating Offshore Wind Turbine Platforms

Floating offshore wind turbine (FOWT) platforms are subject to a wide range of hydrodynamic loading and dynamic movement, making hydrodynamic force evaluation difficult. Amongst various floating platforms, submersible platforms are structurally complex, with multiple members held together by cross-braces. The influence of these members on hydrodynamic loading is poorly understood. An investigation of the effect of these members on loads is essential to optimise the design of FOWT platforms, mooring systems, and protective coatings, leading to a reduction in construction and maintenance costs. This paper numerically investigates the effect of structural members on the forces acting on a static semi-submersible platform in a unidirectional current flow of Reynolds number (Re) ranging from 2000 to 200,000, based on structural diameter and tidal velocity. The OC4 semi-submersible is chosen as the baseline platform. For each Re, this study is divided into three stages, such that in each stage, the number of members increased. These stages are as follows: (1) a finite cylinder (FC), (2) a finite cylinder with a heave plate (FCHP), (3) three cylinders with heave plates (TCHP) in an equilateral triangle arrangement, and (4) the OC4 semi-sub. The drag coefficient (C¯d) increases with increasing structural members and weakly varies with increasing Re. However, the viscous drag coefficient (C¯f) decreases with increasing Re, and a reverse trend is seen in the case of the pressure drag coefficient (C¯p), with pressure drag dominating over friction drag. Further, the contribution of individual members is observed to vary with Re. The contribution of cylinders towards C¯d is higher than heave plates, showing that contributions directly depend on the aspect ratio of members. In the case of TCHP and OC4, the contribution of the rear members is higher than that of the leading members due to the strong wake effect of the former. Also, the braces and pontoons of OC4 have contributed substantially towards total C¯d, unlike the central cylinder, which has experienced low drag due to the wake effect of the front cylinder and heave plate. Also, flow visualisation has shown vortex cores, and recirculating flows in the near wake of the cylinders and under the heave plates. Recirculation zones under the heave plates lead to vertical pressure on the structures. This vertical pressure increases with the number of structural members and the vertical pressure coefficient (C¯v), varying with Re due to three-dimensionality in the wake. Further, this pressure varies across the bottom surfaces of structures. Analyses of the streamwise pressure coefficient have shown it is highest on the front surfaces of cylinders. The highest friction is on the top and sides of the heave plates, and there is considerable friction on the sides of the cylinder.

Analysis of The Application of Value Engineering In The Construction of Soil Retaining Walls on The Bendung-Bantengan Road Section In Mojokerto District, East Java

Mojokerto, as a key economic center in East Java, faces increasing demands for reliable and efficient road infrastructure to support its economic growth and regional connectivity. The lack of adequate retaining walls along the Bendung-Bantengan road section has resulted in significant road damages, including cracks and subsidence, which pose risks to road users and increase maintenance costs. This study investigates the application of Value Engineering (VE) as a strategic method to enhance the efficiency and cost-effectiveness of retaining wall construction in the area. Using secondary data from topographic surveys and triaxial soil tests, the study evaluates various design alternatives to identify cost savings, stability improvements, and impacts on project duration. The results demonstrate that adopting VE (Alternative 1) reduces construction costs by IDR 284,244,698 through optimized structural dimensions, while maintaining quality and stability standards. Additionally, the project completion period is shortened to 121 days, offering a faster turnaround compared to the initially planned six-month schedule. The findings emphasize VE's potential to optimize material use, minimize waste, and achieve environmental sustainability by reducing carbon emissions during construction. Moreover, VE enables enhanced collaboration among stakeholders, including consultants and contractors, to develop effective and efficient solutions for infrastructure challenges. This research underscores the importance of integrating VE during the planning stages of infrastructure projects, particularly in areas with high erosion risks. By applying VE principles, the Bendung-Bantengan retaining wall project not only meets safety and quality requirements but also contributes to long-term infrastructure resilience and economic efficiency in Mojokerto.

Zoning design of cemented sand and gravel dam materials based on DeepFit–memory gradient search–particle swarm optimization fitting optimization

Cemented sand and gravel (CSG) dams are preferred for their cost-effectiveness and adaptability. This study introduces a zoning fitting optimization design method aimed at improving material strength utilization and reducing construction costs. Using Latin sampling and reduced strength safety calculations, an implicit function relationship is established between zoning parameters and safety through an improved deep neural network (DNN). Subsequent dimensionality reduction facilitates optimization using the memory gradient search–particle swarm optimization (MGS-PSO) algorithm. The method's efficacy is demonstrated by optimizing zoning parameters for Japan's Tobetsu Dam, achieving significant improvements in safety and material use. This approach increases safety by 22% and reduces cementing dosage by 36% compared to traditional methods, underscoring its potential in enhancing dam stability and efficiency.

Use of Waste Plastic as a Replacement for Bitumen in Road Construction

Plastic waste pollution has become a global environmental crisis, particularly due to non recyclable and low-density plastics, which contribute significantly to landfill accumulation and environmental harm. This research investigates the use of plastic waste in road con-struction as a sustainable alternative to traditional materials like bitumen and aggregates. By integrating plastic waste into road infrastructure, this study explores methods such as plasticcoated aggregates, plastic-modified bitumen, and fully plastic based roads. These approaches not only enhance the mechanical properties of roads but also help reduce the environmental footprint of construction activities. Plastic-coated aggregates and plastic-modified bitumen improve road durability, weather resistance, and load-bearing capacity, making them more suitable for high-traffic areas and harsh climates. Furthermore, plastic roads show lower maintenance requirements, resulting in long-term cost savings. From an environmental perspective, using plastic waste in road construction helps reduce plastic pollution, curtailing the burden on landfills, and decreas-ing the energy consumption and carbon emissions associated with conventional road-building materials. This research underscores the potential of plastic waste integration as a dual solution: ad-dressing the plastic waste crisis and promoting sustainable infrastructure. The findings highlight the eco-friendly and cost-effective nature of using plastic waste in road construc-tion, presenting it as a promising approach for the future of sustainable infrastructure de-velopment. Using waste plastic as a replacement for bitumen in road construction reduces environmental pollution, enhances road durability, reduces construction costs, minimizes plastic waste, and lowers environmental pollution. However, potential drawbacks include microplastic release, health concerns during production, and the complex waste segregation requirements.

Effect of Cost of Construction of Medium-Level Building Projects on Project Productivity in Kirinyaga County, Kenya

The construction industry is important in society, the economy and the environment. Despite its importance, it is faced with the challenge of the increasing world's urban population at a rate of 200,000 people per day who require affordable housing, social transportation and utility infrastructure. To counter this challenge, the industry will be under a moral obligation to transform by way of reducing construction costs, improving the use of scarce materials and making more eco-efficient over time. Therefore, this study's objective was to evaluate the effect of the cost of construction of medium-level building projects on project productivity in Kirinyaga County, Kenya. The total costs of construction (cost stack) are split into hard costs, soft costs and unforeseen costs. The methodology adopted for data collection was through the administration of structured questionnaires to select seven categories considered to be the main key stakeholders in the construction of building projects. These comprised landlords/homeowners, architects, structural engineers, quantity surveyors, building contractors, construction project managers, and Ministry of Housing and Infrastructure officials. To analyze the results, descriptive statistics and correlational analysis were used. In the analysis, emphasis was placed on the evaluation of the effect of the cost of construction on project completion time, quality and costs. Results from the study show that key factors affecting project productivity through increased costs are delay in payment to contractors and suppliers, high cost of construction materials and choice of construction materials. Other factors are the level of project complexity, site topography, architectural design errors and changes as well as structural design errors and changes.

Investigating the Construction Procedure and Safety Oversight of the Mechanical Shaft Technique: Insights Gained from the Guangzhou Intercity Railway Project

Currently, subway and underground engineering projects are vital for alleviating urban congestion and enhancing citizens’ quality of life. Among these, excavation engineering for foundation pits involves the most accidents in geotechnical engineering. Although there are various construction methods, most face issues such as a large footprint, high investments, resource waste, and low mechanization. Addressing these, this paper focuses on a subway foundation pit project in Guangzhou using mechanical shaft sinking technology. Using intelligent cloud monitoring, we analyzed the stress–strain patterns of the cutting edge and segments. The results showed significant improvements in construction efficiency, cost reduction, safety, and resource conservation. Based on this work, this paper makes the following conclusions: (1) The mechanical shaft sinking method offers advantages such as small footprint, high mechanization, minimal environmental impact, and cost-effectiveness. The achievements include a 22.22% reduction in construction time, a 20.27% decrease in investment, and lower worker risk. (2) Monitoring confirmed that all cutting edge and segment values remained safe, demonstrating the method’s feasibility and rationality. (3) Analyzing shaft monitoring data and field uncertainties, this study proposes recommendations for future work, including precise segment lowering control and introducing high-precision total stations and GPS technology to mitigate tunneling and assembly inaccuracies. The research validates the mechanical shaft sinking scheme’s scientific and logical nature, ensuring safety and contributing to technological advancements. It offers practical insights, implementable suggestions, and significant economic benefits, reducing project investment by RMB 41,235,600. This sets a benchmark for subway excavation projects in South China and beyond, providing reliable reference values. Furthermore, the findings provide valuable insights and guidance for industry peers, enhancing overall efficiency and sustainable development in subway construction.

An Experimental Study on Steel Fiber Effects in High-Strength Concrete Slabs

This study investigated the impact of varying steel fiber ratios by volume on the performance of HSC slabs. Incorporating steel fibers into high-strength concrete (HSC) has been shown to significantly enhance its mechanical properties, particularly by improving its load-bearing capacity. Furthermore, the addition of steel fiber reduces the reliance on traditional reinforcement bars, leading to a more efficient use of materials. This not only simplifies the construction process but also contributes to a reduction in overall construction costs. This study investigated the behavior of HSC slab specimens under loading and elevated temperatures. Three groups of specimens were created based on their thickness (8 cm, 12 cm, and 16 cm) using a single high-strength concrete mixture and four varying steel fiber proportions (0, 37.5, 75, and 150 kg/m³). Two-point monotonic loading was applied to each slab specimen until failure. To determine the splitting tensile strength, 12 cylinders were cast. Additionally, 84 cubes were cast to assess the effects of elevated temperatures and different cooling techniques on compressive strength (fcu). The results revealed that incorporating steel fibers into high-strength concrete slabs has a negligible effect on the concrete's density and compressive strength. However, it notably enhanced the splitting tensile strength and modulus of rupture. These improvements significantly boosted the material's resistance to cracking, making it more durable and better suited for applications requiring superior tensile performance. This is particularly important in structures subjected to dynamic or cyclic loading, where the risk of cracking and failure is greater. Doi: 10.28991/CEJ-2025-011-01-013 Full Text: PDF

3D concrete printing of self-supported filaments via entrained cables: constructing formwork-free spanning structures

ABSTRACT 3D concrete printing (3DCP) enhances design flexibility, reduces construction costs and lowers environmental impact. Traditionally used for wall fabrication, this study introduces a system for printing self-supporting spanning structures using reinforced concrete filaments with tensioned cables, eliminating the need for formwork. The research involved conceptual design and prototyping to integrate cables into the printing process, as well as structural testing of a small-scale model consisting of a reinforced filament. Numerical analysis using the concrete damage plasticity model (CDP) and the traction-separation model simulated the filament's non-linear behaviour and damage. Compared with experimental data, numerical analysis showed good accuracy. Reinforced filaments exhibited a significant increase in flexural strength, from 1.2 kgf·m to 5.0 kgf·m, compared to non-reinforced filaments. Results confirm the feasibility of the proposed method, though challenges remain in ensuring long-term functionality and scalability. Improving the bond between concrete and cables, refining printing parameters and exploring alternative materials are key aspects. While this study focuses on reinforced filaments as proof of concept, future work will address multifilament and multilayer elements like slabs. Highlights A process for 3D concrete printing spanning structures without formwork was developed. A custom device unwinds cables and prints the concrete filament on top, making it self-supported. Kevlar cables were shown to be compatible with the process, while basalt cables presented difficulties. The flexural strength of cable-entrained filaments improves significantly compared to those without cables.

Research on the Mechanical Properties of EPS Lightweight Soil Mixed with Fly Ash.

Expanded polystyrene (EPS) bead-lightweight soil composites are a new type of artificial geotechnical material with low density and high strength. We applied EPS bead-lightweight soil in this project, replacing partial cement with fly ash to reduce construction costs. EPS beads were used as a lightweight material and cement and fly ash as curing agents in the raw soil were used to make EPS lightweight soil mixed with fly ash. The EPS bead proportions were 0.5%, 1%, 1.5%, and 2%; the total curing agent contents were 10%, 15%, 20%, and 25%; and the proportions of fly ash replacing cement were 0%, 15%, 30%, 45%, and 60%, respectively. Unconfined compressive strength (UCS) and scanning electron microscopy (SEM) tests were conducted. The results showed that the EPS content, total curing agent content, and proportion of fly ash replacing cement had a significant impact on the UCS of the lightweight soil. This decreased with an increase in EPS content and decrease in total curing agent content and decreased with increased proportions of fly ash replacing cement. When the proportion of fly ash replacing cement was not too high, the strength of the lightweight soil decreased less, and its performance still met engineering needs. At the same time, the soil can also consume fly ash and reduce environmental pollution. EPS lightweight soil mixed with fly ash still has advantages, and it is recommended to keep the proportion of fly ash replacing cement less than 30%. The failure patterns for lightweight soil mainly include splitting failure, oblique shear failure, and bulging failure, which are related to the material mix ratio.

ADDITIVE TECHNOLOGIES IN CONSTRUCTION: TECHNICAL, ECONOMIC AND MANAGEMENT ANALYSIS

The study is devoted to a comprehensive analysis of the introduction of additive technologies into modern construction production, revealing the technical, economic, and managerial aspects of concrete 3D-printing of architectural structures. The work systematically analyzes the evolution of additive manufacturing technologies and identifies the main structural types of 3D-printers (an additive machine for layer-by-layer construction of objects), including portal, robotic, mobile, and hybrid systems. A detailed study of the technological parameters of concrete 3D-printing with concrete mixtures is presented, in particular, optimal printing speed modes, layer parameters, criteria for shaping and quality of building structures. A comparative analysis of the technological capabilities of leading world equipment manufacturers, such as ICON, COBOD International, Apis Cor, and WinSun, is conducted. The economic analysis demonstrates significant advantages of additive technologies: reduction of construction time by 2-6 times, reduction of construction cost by 20-35%, and increase in the load-bearing capacity of structures. The study comprehensively explores the structure of capital and operational expenses associated with technology implementation. Special emphasis is placed on the management aspects of introducing additive technologies, highlighting the critical need for an interdisciplinary approach and knowledge integration across architecture, engineering, management, and computer modeling. The study determines the prospects for the development of concrete 3D-printing technology in the construction industry and outlines the main directions of further scientific research and practical implementation of innovative solutions. This study was developed between the Department of "Integrated Technologies of Mechanical Engineering" named after M. Semko of NTU "KhPI" and "Geopolimer" LTD to implement innovative technologies in the construction industry.

Optimization of water distribution networks using simulated annealing (SA) with variable neighbourhood search (VNS): a case study in the city of Malard

ABSTRACT Water distribution networks (WDNs) are essential for modern cities, as effective design can reduce construction costs and ensure reliable service. As cities expand, optimizing these large networks becomes increasingly complex. In this work, we introduce a novel approach by combining simulated annealing (SA) with variable neighbourhood search (VNS) into a single heuristic algorithm for WDN optimization, marking the first use of the SA-VNS method in this context. Additionally, we apply Taguchi's design of experiments (DOE) to tune the parameters of the SA-VNS algorithm specifically for water networks. We tested our new algorithm on four standard benchmark networks and a real-world WDN, including a case study of a large city. Our results demonstrate that the SA-VNS algorithm outperforms existing methods in terms of cost, speed, and overall effectiveness, making this research a significant advancement in both heuristic methods and parameter-tuning techniques for WDN optimization.

Risk−Based Cost−Benefit Optimization Design for Steel Frame Structures to Resist Progressive Collapse

The design of structures to resist progressive collapse primarily focuses on enhancing structural safety and robustness. However, given the low probability of accidental events, such designs often lead to a negative cost–benefit. To address this problem, this paper uses risk analysis to optimize the progressive collapse resistance design of steel frame structures. The elements’ cross-section design for the progressive collapse resistance of steel frame structures is optimized using genetic algorithms and SAP2000 23, which identify the structural model with the minimum robustness index while ensuring safety. The results show that the risk-based robustness index can effectively assess the cost of progressive collapse design. More importantly, the optimization model can rapidly identify the most cost-effective structural design solution that complies with progressive collapse resistance guidelines, enhancing the simplicity and usability of the structure design optimization process. Additionally, the integration of the SAP2000 API with Python 3.8 automation streamlines the parameterization process, minimizes manual errors, and enhances the precision and efficiency of the structural design optimization. Finally, the model’s effectiveness is validated through a case study, where the refined single-frame structure shows a reduction in initial construction and collapse-related costs by 2.4% and 9.1%, respectively. Meanwhile, the three-dimensional frame shows a 2.9% rise in initial costs but a 13.5% decrease in total collapse-resistant design costs, illustrating the model’s ability to balance safety with cost-effectiveness.

Research on the optimization of proportions for synchronous grouting material in composite muck during shield tunneling

To tackle the challenge of onsite resource reuse of composite muck, which relies on a shield tunneling section in the case of Nanjing Metro Line 7, this paper examines the effects of component substitution and varying proportions of factors on slurry properties through laboratory tests and multiobjective modeling. From a practical application perspective, the potential of using composite muck as a synchronous grouting material for shield tunneling was explored. In reference to the common mixed strata encountered in shield tunneling construction in the Nanjing area, a general slurry mixing ratio suitable for various mixed strata conditions was derived. The research results indicate the following optimized mixing ratios for the composite muck slurry: a water-to-binder (cement + fly ash) ratio of 0.76, a cement-to-fly ash ratio of 0.53, a binder-to-soil (silty clay + silty fine sand + river sand) ratio of 0.67, a clay (i.e., silty clay)-to-sand (i.e., silty fine sand + river sand) ratio of 0.4, and a substitution ratio (i.e., silty fine sand/silty fine sand + river sand) of 0.2. This slurry is feasible for practical applications and can reduce construction costs by 38.13%. The obtained general mixing ratio for the composite muck slurry, suitable for various mixed stratigraphic conditions, essentially meets onsite construction requirements (the bleeding rate is controlled within a low range of 1.1–3.1%, and the maximum compressive strength reaches up to 6.76 MPa at 28 days), with reasonable costs. It streamlines construction by eliminating the need for onsite screening of muck, allowing for the direct onsite reuse of composite muck in shield tunneling.

COMPARATIVE ANALYSIS OF TECHNICAL, ECONOMIC, WEIGHT, AND SIZE CHARACTERISTICS OF HORIZONTAL AND VERTICAL STEAM GENERATORS FOR 1000 MW NUCLEAR POWER PLANT UNITS

A comparative analysis of the technical characteristics and parameters of horizontal and vertical steam generators for reactorinstallations with water coolant in modern 1000 MW NPP power units has been conducted. It is noted that the peculiarities of thedesign schemes and constructions of steam generators in NPP power units with water coolants are significantly influenced by thestrong dependence between the coolant temperature at the steam generator inlet and the pressure in the reactor circuit. Thedependencies of coolant and working substance temperature changes and the amount of heat transferred in steam generatorelements have been considered. The t-Q diagram of a steam generator with a water coolant featuring a non-boiling economizer,evaporator, and superheater is presented. The parameters of water coolants and working substances in nuclear power plant steamgenerators are provided. The t-Q diagram for steam generators without a superheater section is shown, because in modern 1000MW nuclear power plant units with steam generators which use water as the working substance in the steam-turbine cycle,saturated steam without superheating is used. This is because minor superheating of the steam does not significantly increase theefficiency of the steam-turbine cycle but requires significant complexity in the design of the steam generators. It is noted that thecorrect choice of their structural schemes is crucial in the creation of steam generators with water coolants. It has been proven thatthe characteristics determining the structural schemes of steam generators with water coolants are: the scheme of washing the heatexchange surface with the coolant, the form of the heat exchange surface, the layout of steam generator elements, the principle ofworking substance movement, and others. The technical characteristics of a horizontal-type steam generator for 1000 MW nuclearpower plant units are presented, which have proven to be quite effective in operation. However, their designs and characteristicslimit the potential for further improvement of the technical and economic indicators of nuclear power plants. It is noted thatimproving the technical and economic efficiency of 1000 MW nuclear power plant units while simultaneously reducing capitalcosts for their construction is possible by increasing the unit capacity of powerful vertical-type steam generators installed on them.Compared to horizontal steam generators, vertical steam generators allow for a more rational layout of the primary circuitequipment in the reactor department, thus reducing the volume and cost of construction and installation works. The maindimensions and weight characteristics of possible designs of vertical steam generators for nuclear power plants with VVER-1000reactors are provided. It is concluded that once-through vertical steam generators with spiral wound heat exchange tubes and watercoolant in the first circuit tubes weigh approximately 1.5 to 2 times less than vertical steam generators with natural circulation. It isdetermined that once-through vertical steam generators with a hydraulic scheme involving the movement of the working substancein the tubes and the water coolant in the inter-tube space significantly lag behind once-through vertical steam generators with watercoolant in the tubes in terms of dimensional and weight characteristics and also vertical steam generators with natural circulation interms of weight. It is concluded that for VVER-1000 nuclear power plants, the most promising of all options are vertical once-through steam generators with the movement of the water coolant in spiral wound heat exchanger tube bundles. These steamgenerators occupy approximately four times less area in the reactor department than horizontal ones with the same steamproduction, which significantly reduces construction costs for nuclear power plants.

Optimum Geometry of Double-skin Self-Shading Facade of Classrooms with the Aim of Creating Energy Saving and Visual Comfort in Isfahan Province, Iran

The significant energy consumption in educational spaces worldwide and its environmental impact greatly influence the quality of space, learning levels, and student comfort. Despite offering free school energy costs, developing countries like Iran have not established specific design principles to ensure student comfort. Additionally, the poor design of school building exteriors, such as the common installation of large, unshaded windows in Iranian schools, causes glare issues. The primary objective of this study is to control direct sunlight and increase shading, thereby reducing its impact on energy consumption and enhancing visual comfort. This paper proposes a novel solution that combines a self-shading facade with a double-skin facade for classroom spaces. The study variables, involving the modification of the geometry of the double-skin self-shading facade via DesignBuilder software and the Daysim plugin, were compared to a simple double-layer facade. Based on the results, the optimal scenario for the self-shading double-skin façade with the specifications of a triangular pyramid module shape, ridge position fold 3/2 the module height, cavity depth 7.0, and number of module 2×2 exhibited 40% lower cooling load, 25% lower heating load, and 95% lower lighting load than a simple double-skin facade. At the same time, all scenarios of the new solution provided better visual comfort and daylighting criteria compared to the simple double-skin facade. The modularity and use of indigenous brick materials in the double-skin self-shading facade design reduce construction costs.

Numerical simulations of floating offshore wind turbines with shared mooring under current-only conditions

In recent years, with the continuous development of offshore wind power, reducing construction costs has become one of the key issues. Among them, the mooring system cost accounts for about 20%–30 % of the entire floating offshore wind turbine investment. The concept of shared mooring systems can potentially reduce the cost of floating offshore wind farms (FOWF). In this paper, research is carried out on the dynamic response of an FOWF under representative current conditions of the South China Sea. The comparative analysis focuses on the motion response of a single-spar Floating Offshore Wind Turbine (FOWT)and a dual-spar FOWF. A sensitivity analysis was performed on the length of the shared mooring line. The NREL 5-MW wind turbine with a spar platform is taken as a basis FOWT model for this work. The frequency-domain hydrodynamics is computed based on potential flow theory. The time domain analysis was simulated in a software for marine operations: SIMA(DNV). The viscous effect on the floater is modeled by the drag term in Morison's equation and the hydrodynamic force acting on the mooring line is computed using Morison's equation. Based on the finite element method, the mooring line is defined by a sequence of segments with homogeneous cross-sectional properties. The result shows that with the increase of the current return period, the two platforms move synchronously, and the movement increases almost linearly. Moreover, the motion response of the shared mooring platform is smaller than that of the single mooring platform under the same conditions, especially in the vertical direction. This paper contributes to improved fundamental understanding of shared mooring systems under complex marine environmental loads.

Geotechnical, Mineralogical, Petrographic and Microstructural Characterization of Two Lateritic Gravels from Congo

The recovery of lateritic gravel contributes to the reduction of road construction costs and environmental impact. These materials are of particular interest in road construction because of their abundance, especially in tropical countries, as in the case of Congo. The results obtained on the soils of ʽʽTSANGA and TSIAKIʼʼ show an identical appearance of the two particle size curves, with more fines in the TSANGA sample. Both soils are moderately plastic and their properties predispose them to mechanical treatment (TSIAKI soils) and hydraulic binders (TSANGA soils). The lateritic gravels of TSIAKI can be used as road sub-base for medium traffic while those of TSANGA as sub-base for low traffic. The geotechnical properties of the two samples differ due to the mineralogy, petrography and microstructure which vary from one deposit to another. The SEM microstructure study shows two matrices completely made of kaolinite and the matrix facies are cemented by hematite. X-ray microscopy and SEM allowed the differentiation of goethite and hematite to distinguish the two forms of iron oxides. The TSIAKI soil has a normal iron oxide content (mainly goethite), and has less quartz and kaolinite, which could justify its high CBR index.

Comparative Study on the Prevention and Control Effects of Rockburst Between Hydraulic Fracturing Sections and Blank Sections.

Influenced by various factors such as the complex environment and high key layers in coal mines, hydraulic fracturing technology has gradually become the main means of controlling the hard roof strata to prevent and control rockburst in recent years, which can effectively release the stress on the roof, reduce the intensity of pressure, and ensure the safe and efficient mining of the working face in coal mines. However, the current research on hydraulic fracturing to prevent and control rockburst is mostly limited to optimizing fracturing parameters and monitoring and evaluating fracturing effects, and there are few studies on blank sections, which cannot guarantee the overall prevention and control effect of rockburst, or increase unnecessary construction costs. In this paper, for the directional long borehole staged hydraulic fracturing project, triangular-type blank sections and regular-type blank sections are defined, and the rockburst prevention and control effects of fracturing sections and triangular-type blank sections during fracturing are compared and analyzed by the underground-ground integrated microseismic monitoring technology and transient electromagnetic detection technology, and the rockburst prevention and control effects of fracturing sections and regular-type blank sections during the coal extraction period are compared and analyzed by the underground-ground integrated microseismic monitoring data such as microseismic energy level and frequency as well as the online stress monitoring data. The results show that leaving the triangular-type blank sections can result in reduced construction costs without compromising the effectiveness of rockburst prevention and control. Additionally, the performance of rockburst prevention and control in regular-type blank sections is notably superior to that observed in other working faces without hydraulic fracturing. However, when compared to fracturing sections, the efficacy of rockburst prevention and control in regular-type blank sections remains relatively inferior. Therefore, during the design of fracturing boreholes, it is imperative to strive for maximum coverage of regular-type blank sections. The research findings of this paper comprehensively summarize two prevalent types of blank sections encountered in directional long borehole staged hydraulic fracturing projects. A rigorous comparative analysis is undertaken to evaluate the rockburst prevention and control effects between fractured sections and blank sections. This comparative evaluation serves as a valuable reference for the optimal design of fracturing boreholes, ensuring a balance between achieving effective rockburst prevention and control measures and minimizing economic costs.

Utilization of coalmine overburden-furnace slag and fly ash mixed cement-treated subbase/base course material for sustainable flexible pavements: mechanical performance and environmental impact.

The scarcity of conventional aggregates with tremendous growth in highway construction and the indiscriminate dumping of industrial waste materials in precious landfills has become a huge global concern. This study is aimed at utilizing wastes from various industries, including coalmine overburden (OB) dump, basic oxygen furnace (BOF) slag, and fly ash to produce suitable and sustainable cement-treated subbase/base course layers (CBSB/CTB) for flexible pavement construction. Response surface methodology was used to optimize the composition of the blended material considering unconfined compressive strength (UCS) and Poisson's ratio. Results demonstrated that 50% OB dump, 40% slag, 5% fly ash, and 5% cement achieved a 7-day UCS of 4.84MPa and Poisson's ratio of 0.25, in line with IRC:37-2018 guidelines. X-ray diffraction (XRD) and field emission scanning electron microscope (FESEM) analysis confirmed the presence of ettringite crystals, calcium-silicate-hydrate (C-S-H), and calcium-aluminosilicate-hydrate (C-A-S-H) gels which are the source of strength development in the blend. Further, a soaked California bearing ratio (CBR) of 136.08% and flexural strength of 2.06MPa after 7days and 28days of curing, respectively, demonstrates the overall strength of the stabilized waste. Approximately 4% weight loss was observed after wet-dry durability tests, indicating exceptional performance of the optimal blend in inclement weather conditions. Furthermore, the environmental impact of the blended material was studied through a leaching study. Fly ash had a high zinc (Zn) level, while BOF slag showed a rich concentrationof chromium (Cr), manganese (Mn), and iron (Fe) in the acid digestion test. In spite of this, the toxicity characteristics leaching procedure (TCLP) test indicated that the levels of heavy metals that leached from the stabilized material stayed considerably below the permissible limits set forth in Indian Standard, IS:10500 (2012). Finally, cost analysis showed a 51.6% reduction in construction cost with cement-treated industrial wastes instead of granular base/subbase made with conventional aggregates. The study recommends the suitability of the stabilized waste material as an alternate construction material for large-scale field applications, which could encourage the construction of flexible pavements that are environmentally benign, economical, and sustainable.

Physico-mechanical characterization of compressed earth blocks reinforced with waste fibers from calamus rotang: Case of the elastic soil of western region of Cameroon

In order to enhance the value of local materials and contribute to reducing construction costs in Cameroon, rattan waste is used to reinforce compressed earth blocks (CEB). This main work’s objective is the study of the effect of rattan waste on the physical and mechanical properties of CEB. For this, a soil sample taken in the western region of Cameroon, more precisely in Bangangté, was analyzed, the analysis includes the granulometric analysis, the Atterberg limits, and the Proctor test. Then the CEB samples with different rattan waste contents, that is 0%, 2%, 4% and 6%, were developed for a compaction stress of 7.5 MPa. These different samples were characterized through mechanical and physical tests carried out in the laboratory. It appears that the blocks reinforced with 2% of rattan waste have better mechanical characteristics, respectively 0.70 MPa in three-point bending and 3.04 MPa in compression. On the other hand, the presence of rattan wastes has a positive effect on the mechanical behavior of the composite, by increasing its ductility compared to the fragile behavior of the control block, which is observed during crushing. Thus the mechanical properties of CEB improve with the incorporation of rattan waste, which is optimal for a content of 2%. But they increase the material's porosity, and then its sensitivity to water unlike the control CEB.