This study experimentally investigated the effect of connecting vertical plates and horizontal plates and their combinations to single and double pipes on scouring under pipes. Experiments were performed in a laboratory flume 13 m long, 0.4 6m wide, and 1 m deep. Results showed that attaching a 0.25D vertical plate under a single pipe prevented scouring under it. Further, in order to control scouring under pipes using a horizontal plate, regardless of the number of pipes and their distance from each other, the plate should extend 0.5D upstream and downstream of the pipes. A combination of horizontal and vertical plates under pipes showed that in cases where the length of the horizontal plate was not enough to prevent the formation and development of scour under the pipes, the addition of vertical plates on both sides of the horizontal plate can protect the pipes against scouring.
This paper presents the major causes of deterioration and discusses the factors, which can improve the durability of concrete structures. This paper also presents the results of an extensive experimental investigation for the reuse of industrial by product materials such as blast furnace slag (BFS) and silica fume (SF) in producing high performance concrete. Producing of high strength concrete has a worthy priority field of study worldwide, their production is largely expanded the last two decades. Potential applications of light weight high strength concrete are in producing thin durable sections and in strengthening and repairing defaulted structures. It is shown that it is possible to develop a concrete matrix of high strength and excellent durability by taking the advantage of the interactions of cementitious system and the Portland-cement slag system is shown to offer a good example of this nature. However, development of light weight strength and performance concrete will be necessary to protect the concrete from aggressive and unfriendly environmental and climatic conditions. Lightweight concrete can significantly reduce a dead load of structural concrete elements compared to normal-weight concrete. Self-curing concrete is one of the innovative concretes that can be cured without using conventional curing regimes. Lightweight concrete is made from lightweight coarse aggregates instead of natural coarse aggregates. It has gained popularity due to its lower density and superior thermal insulation properties. In this investigation, the durability of lightweight self-curing concrete under the attack of sulfates and chlorides was studied. The effects of sulfates (as 20% concentrated sodium sulfates solution) on compressive, splitting tensile and flexure strengths after different ages (2, 4, and 6 months) were studied. The effects of chloride attack (as 20% concentrated sodium chloride solution) were studied on bond and flexure strengths after two ages (2 and 4 months). Also, the flexure behavior of the lightweight aggregate self-curing reinforced concrete beams is studied under a four-point load system before and after chloride attack. Test results indicated that dolomite then crushed concrete followed by Addibor can be used as coarse aggregates for structural self-curing concrete under chlorides or sulfates Using lightweight aggregates (Addipor-55) or lightweight bricks as a replacement of dolomite can be used to produces lightweight self-curing concrete with satisfied durability characteristics under chlorides or sulfate attack.
In this paper, the author performed two centrifuge model tests at the University of Science and Technology of Hong Kong for two cases where the tunnel was located at cover over diameter (C/D) of 1.5 and 3.3 to investigate the passive failure and deformation mechanism due to tunneling in two-layer soils, sand and clay. The tests were carried out on a 1/100 scale miniature model. The experimental process simulated the progress of the tunnel face with a speed of 0.2mm/s (equivalent to 15m per day in practice), and displaced to 40mm then stopped. Linear variable differential transformers (LVDTs) are used to measure the ground transitions during the testing process. The particle image velocimetry (PIV) technology measures the movement of soil in front of the tunnel face. The loadcells attached to one end of the tunnel face in order to obtain the passive pressure exerted on the tunnel face. As the tunnel face displacement, the ground in front of the tunnel face is shifted forward, while the ground which is far from the surface of the tunnel is pushed outward, effected on the ground and thus causes the ground to emerge so form a breakout. The partial failure mechanism in front of the tunnel face is similar to localised cutting mechanism. When the observation failure mechanisms are idealized by continuous lines, the failure mechanism of ground in front of the tunnel face is shaped like a funnel.
Determination of the flow velocity and shear stress is fundamental for river restoration projects. There are few studies in estimation of these parameters in the presence of 3D pool and riffle which are dominant bed forms in coarse-bed Rivers. Considering the interaction of 3D bed forms and the flow characteristics in the presence of wall vegetation, the present study aims to determine the velocity distribution, shear velocity, and shear stress in a laboratory scale. Accordingly, the effects of sediment sizes and various discharges on velocity and shear stress distributions and the validity of logarithmic law were assessed in a straight laboratory flume 13 m long, 0.45 m wide, and 0.6 m deep. Experiments were conducted in 4 runs over 3D pool and riffle where the natural vegetation were used along one side of the flume wall. Results showed that the logarithmic law remains valid for relative depths Z/H= 0.36 and 0.84 where Z is distance from the bed and H is the flow depth, in different sections of 3D pool and riffle. The location of maximum velocity changed with increasing the flow discharge. The maximum velocity value occurred at higher relative depths in the pool section rather than in the riffle one. Higher flow velocity values were observed near the water surface in pool section and near the bed in riffle section, respectively. The investigation of shear stress revealed that the maximum and minimum shear stress values occurred in the pool and riffle flows, respectively, and the presence of vegetation led to a change in the location of maximum shear stress. When the median size of the bed particles decreased, less change was observed in the shear stress values.
The UK as a welfare state spends about 30% of the gross domestic product on social expenditures. The acute and biting shortage of housing, particularly social and affordable housing is responsible for the spiralling house prices and rents leading to an affordability crisis. Evidence-based research shows that the UK needs to build over 300,000 houses a year to meet the rising demand, particularly from young adults and families with low-to-middle incomes. As a result, there has been a worrying increase in overcrowding, homelessness, evictions and rent arrears. This research study aimed to investigate prefabrication, also known as modular construction as a solution to tackling the housing crisis in the UK. A mixed method approach was used to collect raw data. As such, five major construction firms were selected as the case study organisations for the research study. The respondents had a senior position in the organisations. The data collection methods that were adopted are qualitative (interviews) and quantitative (questionnaires). The data were analysed using thematic analysis in which emergent themes were identified throughout the interviews and the questionnaires. Findings suggested that the housing crisis is not about houses; instead, it is about individuals. Perceptions about prefabricated houses among the low, middle and high-income earners are largely negative whose implication is that individuals would rather wait to build traditional homes in the future than opt for a prefabricated home. Although traditional home ownership is slipping out of reach for the majority, the demand for prefabricated homes is still low. In urban areas, modular construction is practised on a small scale with the main market limitations being the small size of the domestic market and the existing building regulations which prohibit the use of inflammable materials in urban areas. Moreover, it was found that prefabricated homes may provide short-term and long-term solutions to the housing crisis since they address and resolve some of the most critical issues associated with traditional housing but not limited to high costs, longer construction periods and uncertain budgets.
