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Processing and recycling of aggregate residues after ore extraction for stabilization of mined areas
Get PDFThe article focuses on the treatment and recycling of aggregate. It also addresses the issue of treatments effects on mine tailings, fly ash and acid mine water on the measured parameters of concrete with load-bearing and backfilling paste with non-load-bearing function. Four different mixes were developed, and standard tests were performed on them. These mixtures were made with different types of mine tailing’s fillers with varying degrees of treatment. Mineralogical and chemical tests were carried out on the treated aggregates, with sieve analysis and their subsequent adjustment for suitable aggregate gradation curve in concrete. Strength and volumetric weight tests were carried out on hardened samples at 28, 56 and 90 days. The results of the determined functional specimens showed that it is possible to develop an almost completely waste-free technology using recycled aggregate and fly ash from the ore mining and energy industries and its subsequent processing and use for backfilling of mine deposits with load bearing and non-load bearing function concrete
Structural health monitoring of construction
Get PDFThe paper is concerned with the possibilities of long-term monitoring of constructions using modern wireless sensors and systems. There are currently many constructions under long-term monitoring performed by modern sensors. The monitoring enables an assessment of the current health of the construction or it can be used to recalculate and adjust the BMI models and subsequently evaluate the static and dynamic resistance of the construction. The sensors and systems installed enable the detection of hidden defects or newly emerging failures and damage. Using the results obtained from the monitoring of the construction, it is possible to predict and carry out a timely repair or maintenance of the construction, which will ultimately decrease the financial and time-related costs, ensure greater safety and prolong its lifetime and resistance
OPTIONS SELECTION AND IMPACT STUDY OF INTERCITY RAILWAY TUNNEL CONSTRUCTION UNDER AIRPORT INTERZONE
Get PDFThe selection of tunnel construction program for intercity railroad tunnel under the airport must consider the limitations of environmental conditions and the scale of tunnel construction, and the impact of construction on the airport must be controlled within safe limits. Combined with the intercity rail transit tunnel project through the airport area surrounding environment and engineering geological conditions, the use of theoretical analysis, numerical simulation and other methods, comprehensive navigation, technology, construction period, cost, construction impacts and other aspects of the comparative analysis of the tunnel construction method of open excavation method and shield method, the results show that: (1) Due to the soft soil and groundwater in the tunnel excavation area, the risk of open excavation is greater, while the shield method is more suitable for longer silty soil tunnels without affecting the navigation, accordingly, the shield tunnel construction is more suitable for the tunnel construction under the airport. (2) Open excavation method has the shortest construction period to meet the requirements of rail transit, the unit cost is between 1 and 2 shield machines, and the total cost is close to 2 shield machines; for lower total cost, choose 1 shield machine, for shortening the construction period, choose 2 shield machines. (3) The maximum ground settlement caused by shield tunneling construction is 20mm, the maximum vertical differential settlement perpendicular to the tunnel is 2.8cm, and the maximum differential settlement is 0.93 ‰. On the one hand, it meets the requirements of airport settlement control, and on the other hand, it has little impact on the vertical connecting road and west station apron, and will not affect the opening of the airport runway and the operation of the terminal
Positional accuracy of cadastral maps digitized from the stable cadastre system
Get PDFThe accuracy of positional data in cadastral mapping is crucial for various technical activities within the cadastre and related decision-making processes. With digital maps becoming ubiquitous in cadastral operations, assessing the positional accuracy of cadastral maps digitized from stable cadastre systems has become essential. These maps, categorized as DKM and KMD, present different challenges in determining their overall positional accuracy. While DKM maps offer high accuracy, KMD maps, derived from stable cadastre systems, pose challenges due to their varied origins, including potential positional errors inherited from historical data.
This study proposes a methodology for assessing the positional accuracy of KMD maps by comparing digitized boundaries with actual field measurements. The evaluation considers factors such as cadastral area characteristics, available survey data, and the timing of digitization efforts. The study aims to categorize objects based on their positional accuracy by analysing shifts in boundary points and building positions.
Results from testing in selected cadastral areas reveal varying degrees of accuracy in KMD maps. While some areas demonstrate high accuracy, others exhibit significant positional inaccuracies, particularly in peripheral regions or linear parcels. The study suggests that areas outside municipal boundaries may require immediate remapping to ensure accuracy.
Overall, the findings highlight the importance of assessing and improving the positional accuracy of cadastral maps to enhance their utility in land management and decision-making processes. Further research in this area could focus on developing automated methods for detecting and correcting positional errors in digital cadastral maps
Comparison of elastic properties of periodic and aperiodic porous structures produced by additive methods
Get PDFThe aim of this work was to design, print, and examine elastic properties of porous structures with various parameters and beam distributions. These structures, generated using an algorithm, featured three types of lattices: octet, cubic, and Voronoi diagram-based, with different porosities (40 %, 60 %, 80 %) and beam sizes (0.45 mm, 0.66 mm). They were printed using Direct Light Processing and examined using X-ray computed microtomography. Compression tests were conducted to determine the Young’s modulus. The results were compared with computer simulations performed using Abaqus. The tools used, such as 3D printing and X-ray computed microtomography, were described, and the results and conclusions of the tests were presented. As a result, comparable outcomes were obtained for structures with higher beam diameter, while significantly different results were observed for structures with lower beam diameter
POLYURETHANE CEMENT REINFORCEMENT FOR SEISMIC TESTING OF CURVED BEAM BRIDGES PIERS
Get PDFDue to the "bending and torsion coupling" effect of curved bridges, the shear fracture and bending collapse of curved girder bridge piers and columns under the action of earthquakes are more likely to occur, resulting in the serious consequences of the overall collapse or overturning of the bridge structure. Polyurethane cement is a kind of reinforcement material used for structural seismic reinforcement in this case, which has excellent reinforcement performance. In this paper, based on the three-way shaking table test of curved girder bridge, OpenSees finite element software is used to establish the fiber unit model of the abutment specimen, and the model is used to carry out the parameter sensitivity analysis to investigate the influence of the height of abutment and polyurethane reinforcement on the seismic performance of polyurethane cement-reinforced abutment specimen, and it is known that, the higher the abutment is, the worse is the reinforcing effect of polyurethane cement; the higher is the thickness of polyurethane cement, the better is the reinforcing performance of polyurethane cement. The higher the abutment is, the worse the reinforcing effect of polyurethane cement is; the higher the thickness of polyurethane cement reinforcement is, the more obvious the effect of polyurethane cement reinforcement is. Based on the data of parameter sensitivity analysis, the parameters are optimized, and the most economical parameters are derived, thus providing sufficient theoretical basis for polyurethane cement reinforcement of curved beam bridge piers
PREVENTION AND DRAINAGE TECHNOLOGY FOR ANTI-STUCK AND DISCHARGING DURING SHIELD TUNNELING IN COMPLEX RED ROCK STRATA WITH ULTRA-LARGE DIAMETER UNDER NORMAL AND PRESSURIZED CONDITIONS
Get PDFDuring the construction process of shield tunneling with ultra-large diameter under normal and pressurized conditions, problems such as mud cake formation on the cutterhead, stagnation of mud in the chamber, blockage of slurry discharge chute, high cutterhead torque, and slow excavation speed are prone to occur. In severe cases, these issues can impact construction progress and pose a threat to construction safety. Taking the Guangzhou Haizhu Bay Tunnel project as a case study, this paper proposes prevention and drainage technology for anti-stuck and discharging during shield tunneling in complex red rock strata with ultra-large diameter under normal and pressurized conditions, focusing on mud slurry control, optimization of cutterhead flushing system, excavation parameter control, and cutter tool optimization
Effect of surface area on the wear properties of Al-based automotive alloy and the role of Si at eutectic level
Get PDFThe efficiency of an engine material is closely correlated with its surface area. In order to investigate wear properties, effect of surface contact area as well as silicon addition at the eutectic level of Al-Cu-Mg alloy has been studied. This test is performed under room atmosphere and dry sliding conditions using a standard pin-on-disk apparatus. Weight reduction method is adopted to measure the wear rate in microns to get more accurate results. A load varying from of 5 to 50 N and a constant sliding speed of 0.77 ms−1 are maintained throughout the test. The test results show that a lower contact surface area has a negative impact on the wear properties having higher wear rate, while the coefficient of friction of the alloy and Si addition into the alloy improve the properties to some extent. Reduction of the contact surface area increases the unit pressure and decreased material volume causes softening of the alloy matrix, resulting in a higher wear rate and coefficient of friction. The Si addition offers such an improvement mostly for an increase in strength via the Si-rich intermetallic formation. A microstructural study confirms a lower abrasive wear with a minor plastic deformation on the worn surfaces of Si added alloy and wear with higher contact surface. The Si-added alloys contain the fine and strong Si-rich intermetallic, which are responsible for such a smooth worn surface
Possibilities of reinforcement of subtle translucent concrete panel
Get PDFTextile-reinforced concrete not only has many advantages that lead to less consumption of primary resources, but also enables the creation of thin and subtle elements. The high performance of such elements allows us to create interesting architectural features, such as translucent concrete. This article focusses on the possibility of reinforcing translucent concrete panels
A COMPARATIVE ANALYSIS BETWEEN PERSONAL AND TERRESTRIAL LASER SCANNING FOR THE DOCUMENTATION OF HERITAGE SITES
Get PDFThis paper presents a comparative analysis of mobile and terrestrial laser scanning techniques in the 3D surveying of Bashtova castle in Albania, showcasing the integration\u27s efficacy in capturing a comprehensive and accurate representation of this historical structure. Personal laser scanning (PLS), characterized by its mobility and ability to capture data while in motion, offers advantages in terms of efficiency and coverage of large areas. Conversely, terrestrial laser scanning (TLS), with its stationary setup and high precision, excels in capturing detailed information and intricate architectural features. Thanks to the research on the case study of the Bastova Castle in the article, it can be stated that the integration of data from PLS and TLS is seamless with the help of modern software while respecting the basic photogrammetric-geodetic rules and demonstrates the possibility of creating a complex 3D model, usable for further analyses for architects and conservation professionals, as well as for restorers and civil engineers. Research has shown that the difference between point clouds from PLS and TLS is within one centimeter