Добірка наукової літератури з теми "Reinforced concrete Trenches (RCT)"

Surface rupture associated with the 1992 Landers earthquake (Mw 7.3) damaged several structures in the southwest Mojave desert. Six trenches were excavated through and adjacent to three structures that were damaged by directfault displacement. Trenching insights assisted in understanding foundation failures. This investigation confirms the surface shear zones, documents subsurface fault rupture geometry, and describes the effects on those structures. The surface pattern of rupture consisted of left-stepping, right-lateral shears with local vertical components within broader zones of shearing. The trenches generally exposed poorly stratified granular materials in which faults that were previously mapped on the surface were difficult to recognize. The age and material properties of the alluvium influenced the pattern of deformation. A strong correlation was found between the geometry of faulting and the pattern of residential concrete slab deformation. These observations suggest that an adequately reinforced concrete slab with poor coupling to the ground may minimize damage due to direct surface rupturing.

This study suggests a novel beam-column element formulation that utilizes an equilibrium-driven shear stress function. The beam shear is obtained from the bi-axial states of micro-planes, through matrix condensation and zero vertical traction assumptions. This properly remedies the shear stiffening of a one-dimensional beam-column element, keeping its degrees of freedom to a minimum. For verification of the proposed method, a total of seven shear test results of reinforced concrete (RC) beams were collected from the literature, in which the key variables were the reinforcement ratio, the presence of shear reinforcement, and section shape. The advantages are clearly shown in the shear stresses distributions being accurately described and the global load-displacement relations being successfully obtained and matching well with various test results. The proposed model shows satisfactory descriptions of the monotonic load-displacement response of the RC beams failing in multiple modes that vary from diagonal-tension to flexural-compression. In addition, more accurate and reliable information of sectional responses including sectional shear deformation and stresses is collected, leading to better prediction of a potential shear failure mode. Finally, the advantages of the proposed model are demonstrated by comparing the analysis results of an RCT-beam by using the different shear assumptions that include the constant and parabolic shear strains, constant shear flow, and the proposed shear stress function.

Introduction: when reconstructing or overhauling dams, great attention should be paid to drainage systems as the most critical components of the installations. The article describes the typical malfunctions of earth dam pipe drainages. The research considers geological and hydrogeological features that were not taken into account when developing projects. Materials and methods: control and measuring instrumentation (piezometer network), full-scale experiments on disabling pipe drainage and mathematical modelling were used as the filtration regime research methods. Results: analysis of the hydrogeological features of the base of the right-bank floodplain dam of the Nizhegorodskaya hydroelectric power plant and field filtration observations revealed a strong drainage effect of the base on the filtration flow at several areas of the dam body. At the other areas, a high groundwater level position at the dam downstream and its outlet into the pipe drainage at the downstream were recorded. Substantiated by filtration calculations, the proposed repair of the drainage system consisted in designing open drainage along the dam axis and backfilling the territory at the downstream by 2.0 m that excludes impoundment of the territory without the pipe drainage. Conclusions: the following engineering solutions can be recommended for repairing earth dam drainage systems: construction of backfill drainage trenches in the dam downstream, new pipe drainage at higher elevations or an open drainage channel in solid reinforced concrete arranged along the axis of the dam. The proposed version of the pipe drainage repair provides for constructing an open drainage channel in solid reinforced concrete on a reverse filter with an arrangement of gravel-filled asbestos-cement pipes in the dam slopes and bottom. Such a design solution allows repairing the drainage system without dewatering and, if necessary, completely refusing the existing pipe drainage.

The Moroccan road network is susceptible to multiple landslides annually, particularly in the northern regions due to high rainfall and specific geology. These events result in significant economic and social negative consequences, highlighting the need for sustainable and cost-effective solutions for network maintenance. This study outlines the methodology employed in addressing the issues within the RR410 regional road (Rifain region of Morocco), which entailed a thorough examination of the malfunctions, specific surveys, laboratory testing, and problem modeling. By incorporating long-term test-derived shear strength parameters, the model indicated that the road platform was stable, and back analysis using TALREN 4 software allows for model calibration. At kilometric point 23, using earthwork-based solutions (e.g., purging and replacing the base layer, employing granular water-insensitive substitution material) was found to provide a sustainable alternative to the expensive reinforced concrete-based solutions commonly used. Furthermore, these solutions contributed to the use of environmentally friendly and locally sourced materials. Road alignment rectification to anchor the platform in suitable soil was also an effective solution, as demonstrated at kilometric point 48. Additionally, enhancing the drainage and sanitation infrastructure, such as installing draining trenches, spurs, and reinforcing existing water structures, is a crucial aspect of addressing most landslides in the region.

Earthmoving equipment in highly developed countries is a leading place among self-propelled and trailed equipment for various purposes. The basis of such equipment are scientific and technical principles of creation of high-speed low-energy technologies and machines for destruction of natural and artificial environments (soils, rocks, mules, reinforced concrete, bricks, etc.) in various conditions (ground - road, cultivation of agricultural lands, engineering, military and emergency rescue work, cleaning of soils from pollution, reclamation, creation of trenches, canals, which underground - mining, tunnel construction, etc. Continuous action machines are such machines in which the working body contacts with the object of influence (soil) during the whole time of operation and all technological operations are performed simultaneously and continuously. Working bodies of continuous-action machines have the ability to develop strong soils without preliminary loosening During the continuous operation of machines, the process of their work is divided into two processes: the process of cutting soil into slaughter and the process of excavation of soil from the cutting zone, followed by its ejection from slaughter. The article provides an overview of new dynamic working bodies of shrew machines. The descriptions, drawings, highlighted the main disadvantages and advantages. As a result of the synthesis of existing working bodies, a new dynamic working body was developed.

The use of nitrite- and nitrate-based inhibitors provides corrosion protection by the development of passive oxide film on the metal surface in reinforced concrete applications. However, the impact of the nitrite and nitrate ratio in the mixture has not been widely studied. In this study, the corrosion protection provided by NaNO2:NaNO3 inhibitor blends with ratios of 0.5:1, 1:1, and 1:0.5 were studied to maximize corrosion inhibition efficiency. The nitrite species imparted higher corrosion protection, as shown by cyclic potentiodynamic polarization, with an icorr of 1.16 × 10–7 A/cm2 for the 1:0.5 mixture, lower than for both the 1:1 and 0.5:1 mixtures. Electrochemical impedance spectroscopy was also performed, with the 1:0.5 mixture consistently displaying high resistance values, showing an Rct of 1.31 × 105 Ω cm2. The effect of temperature was also assessed; the Ea’s of the corrosion reaction were calculated to be 12.1, 9.2, and 4.9 kJ/mol for the 0.5:1, 1:1, and 1:0.5 (NO2−:NO3−) mixtures, respectively. Density functional theory was applied to analyze the molecular properties and to determine the relationship between the quantum properties and corrosion inhibition. The ΔE of NO2− was found to be −5.74 eV, lower than that of NO3− (−5.45 eV), corroborating the experimental results. Lastly, commercially available inhibitor mixtures were investigated and nitrite/nitrate concentrations determined to evaluate their corrosion protection performance; amongst the two inhibitor blends tested, Sika was found to outperform Yara due to its greater NO2− concentration.

Despite Togo government’s efforts to maintain and expand its storm drainage networks, urban flood disasters remain recurrent. Beyond Shallow zones occupation for construction and climatic causes, it is essential to circumscribe the determinants linked to infrastructure. Based on the inventory and characterization of rainwater drainage infrastructure, this study is a contribution to the reduction of flood risk in the city of Lome in Togo. Surveys were conducted on rainwater drainage works of the 172 paved roads in Lome. A sample of each network group is selected by considering the areas of recurring hazards and broadest catchment areas in the city for the evaluation of their structural and functional states according to the readapted VIZIR method. The relationship between these two states was computed using multiple correspondence analysis (MCA). This study reveals notable insufficiencies in rainwater drainage management in the city, expressed by the existence of roads built without drains, gutters without outlets, and open gutters and makeshift trenches built by the population. Functionally and structurally, almost all the structures are constructed of reinforced concrete. The most cracked are the mainly open pit (92.02%) works of the lagoon complex. The retention basin network includes 36 retention ponds 18 of which are interconnected, 11 drained by gravity and 4 by pumping. The latter are inherently hazardous insofar as pumping energy is not guaranteed. The MCA has shown that the network of piping related to the retention ponds are in similar conditions, and that generally, the closed gutters are not cracked while the open gutters are cracked.

Abstract. The paper gives an overview of the history of evolution and mitigation of the Macesnik landslide in N Slovenia. It was triggered in 1989 above the Solčava village, but it enlarged with time. In 2005, the landslide has been threatening a few residential and farm houses, as well as the panoramic road, and it is only 1000 m away from the Savinja River and the village of Solčava. It is 2500 m long and up to more than 100 m wide with an estimated volume in excess of 2 million m3. Its depth is not constant: on average it is 10 to 15 m deep, but in the area of the toe, which is retained by a rock outcrop, it reaches the depth of 30 m. The unstable mass consists of water-saturated highly-weathered carboniferous formations. The presently active landslide lies within the fossil landslide which is up to 350 m wide and 50 m deep with the total volume estimated at 8 to 10 million m3. Since 2000, the landslide has been investigated by 36 boreholes, and 28 of them were equipped with inclinometer casings, which also serve as piezometers. Surface movements have been monitored geodetically in 20 cross sections. This helped to understand the causes and mechanics of the landslide. Therefore, landslide mitigation works were planned rather to reduce the landslide movement so that the resulting damages could be minimized. The construction of mitigation works was made difficult in the 1990s due to intensive landslide movements that could reach up to 50 cm/day with an average of 25 cm/day. Since 2001, surface drainage works in the form of open surface drains have mainly been completed around the circumference of the landslide as the first phase of the mitigation works and they are regularly maintained. As a final mitigation solution, plans have been made to build a combination of subsurface drainage works in the form of deep drains with retaining works in the form of concrete vertical shafts functioning as deep water wells to drain the landslide, and as dowels to stop the landslide movement starting from the slide plane towards its surface. Due to the length of the landslide and its longitudinal geometry it will be divided into several sections, and the mitigation works will be executed consecutively in phases. Such an approach proved effective in the 800 m long uppermost section of the landslide, where 3 parallel deep drain trenches (250 m long, 8 to 12 m deep) were executed in the autumn of 2003. The reduction of the movements in 2004 enabled the construction of two 5 m wide and 22 m deep reinforced concrete shafts, finished in early 2005. In Slovenia, this sort of support construction, known from road construction, was used for the first time for landslide mitigation. The monitoring results show that the landslide displacements have been drastically reduced to less than 1 cm/day. As a part of the stepwise mitigation of the Macesnik landslide, further reinforced concrete shafts are to be constructed in the middle section of the landslide to support the road crossing the landslide. At the landslide toe, a support construction is planned to prevent further landslide advancement, and its type is still to be defined during the procedure of adopting a detailed plan of national importance for the Macesnik landslide.

Reinforced concrete walls sandwiching granular infill may be used to enhance missile protection of selected facilities. Two behaviors complicate the seismic response of the assemblage of granular material contained by the two concrete wall elements. First, the granular material tends to settle when the walls pull apart in a breathing mode. This settling increases the lateral pressure acting on each wall, generating a set of forces that acts to spread the walls apart. Settling of the granular material combined with spreading of the walls results in breathing mode deformations that can occur in a ratcheting behavior, with the walls moving progressively further apart with each cycle of strong ground motion. Second, friction forces develop between the two walls and granular material. These forces may cause partial flexural coupling of the two walls (i.e., partial composite action). Soil mechanics solutions for lateral soil pressure acting in trenches are adapted to predict the lateral pressure of granular infill. The granular material is represented by a bilinear lateral response representing the active flow regime. The seismic response of granular infill concrete walls is studied using nonlinear finite element analysis. Simple structural models appropriate for routine seismic analysis that capture important aspects of the seismic response are proposed.