Current Issue : October-December Volume : 2023 Issue Number : 4 Articles : 5 Articles
The construction project is regarded successful when it is given over to the owner within the time, cost, and standards necessary while minimizing delays in public construction projects. Debre Markos University (DMU) is one of the public universities undergoing massive development projects that are experiencing significant delays. This article evaluates the most prevalent delay issues encountered by Ethiopian government-funded construction projects, particularly those using DMU, analyzes their impacts, and suggests a delay management system. The study applied qualitative as well as quantitative techniques to evaluate primary and secondary data. Per the entirety statistics, the top five most important and highly ranked factors are erroneous time estimates, force majeure, lowest bid, procurement policy, and volatile markets, as well as frequent design changes. Nearly everyDMUproject schedule overruns up to 268.67% of its contract duration. As a result, the institution suffered from poor public relations and a high cost of supervision and contract administration (6.87% of the overall project cost). Conducting a thorough and accurate project feasibility study, awarding bids to experienced contractors, avoiding drawing discrepancies, preparing an accurate initial time and cost estimate, and strict schedule monitoring were discovered to be effective techniques for reducing delays in public construction projects....
Soft soil has the characteristics of high compressibility, large void ratio, and strong structure. Therefore, it is more likely to cause surface subsidence or even surface cracking and collapse when laying oil and gas pipelines in soft soil areas through the pipe jacking method. In this study, test soil was pressurized using a flexible loading bladder, and variable formation losses brought on by pipe jacking were mimicked by varying the loading bladder’s water injection level. The surface deformation brought on by pipe jacking construction is related to the four parameters of stratum loss rate, overburden load, soil disturbance, soil tension fissures, and horizontal deformation. The findings demonstrate that the surface deformation brought on by the excavation gradually reduces and starts to stabilize after the thickness of the overlying soil layer on the pipe jacking surpasses 1.5 times the diameter of the pipe jacking. The constructed settling tank is broader the deeper the jacking pipe is submerged. Further ground surface settling will be exacerbated by the weight above the jacking pipe. The maximum ground surface deformation value will decrease with an increase in the overlying load when the overlying load is high (0.018 MPa)....
Ensuring proper and effective cementing of casing pipe columns in boreholes requires maintaining appropriate technological parameters for the developed slurry recipes. It is also necessary to use technology which guarantees effective displacement of the drilling mud for cement slurry injection into the annular space of the borehole. The most important factors that ensure high efficiency of drilling mud displacement by the cement slurry are, among others, the rheological properties of the liquids involved in the process of cementing the casing columns (drilling mud, cement slurry, buffer liquid). The introduced version of the European cement standard, PN-EN 197- 1, includes new types of very economical multi-component cements CEM V/A and CEM V/B, which contain 20–40% Portland clinker with a relatively high content of hydraulic and pozzolanic constituents. They occur in the form of granulated blast furnace slag, natural as well as industrial pozzolans and silica fly ash from the combustion of hard coal. The article presents the results of laboratory tests on the technological parameters of both fresh and hardened cement slurries prepared on the basis of CEM V multi-component cement varieties A and B. These slurries meet the standard technological parameters to a demanding extent, which makes it possible to apply them to cementing columns of casing pipes in deep hole drilling. Their detailed properties can be modified by introducing other mineral additives and chemical admixtures to the cement slurry recipes....
The purpose is to optimize the foundation’s treatment process and improve the foundation’s construction effect to better apply the cement soil composite tubular piles. This exploration is to study the cement composite tubular piles. First, the principle and application of optical fiber sensing technology are discussed. Then, the application design and conditions of the cement composite tubular pile are discussed. Finally, a new foundation treatment technology supported by optical fiber sensing technology is proposed and comprehensively evaluated based on the application of cement soil composite tubular piles. The research results show that: (1) the new foundation treatment technology reflects the optimization of the optical fiber sensing technology for the foundation treatment. Moreover, it is further optimized through the application of cement soil composite tubular piles. (2) When subjected to the same load, the longer the core pile is, the smaller the cement soil composite pile’s settlement is. When the inner core pile is 20m~24m long, the settlement of the cement soil composite pile is small. When the length of the inner core pipe pile is 16m~20 m, the settlement range of cement soil composite pile becomes larger. (3) With the increase of friction coefficient, the settlement distance of cement soil composite tubular pile will decrease. The above data show that compared with the traditional foundation treatment technology, the new foundation treatment technology designed based on the application of composite tubular piles, supported by optical fiber sensing technology, can well solve the foundation construction problems, avoid pavement settlement, cracking, and other phenomena, and ensure the overall safety of the road. This exploration fully reflects the advantages of the new technology of foundation treatment and ensures the quality of road engineering. It provides a reference for the development of foundation treatment technology of construction projects and contributes to the development of the construction industry....
Traditional supplementary cementitious materials (SCMs) have been proven to reduce the negative impact of Portland cement production on the environment. However, the availability of SCMs becomes limited due to their extensive usage. For this reason, our work aimed to investigate the effect of partial substitution of ordinary Portland cement (OPC) with two different types of carbon-rich waste powders—biochar (BC) and coal dust (CD), dosed separately up to 10 wt.% of OPC, on the physical, microstructural and mechanical properties of hardened specimens. Obtained data pointed out that replacing OPC with small amounts of BC and CD (not exceeding 5.0 wt.% and 2.5% wt.%, respectively) initiated an increment in mechanical strengths due to a decrease in total open porosity and enhanced formation of hydration products of such composites compared with the reference. Overall, both examined alternatives, if added in appropriate amounts, have the perspective to be effectively applied in cement manufacturing and concrete production, and thus to importantly contribute to the long-term sustainability of the construction industry in view of energy savings, reduced releasing of the greenhouse gasses and mitigating of global climate changes....
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