1021 Final Exam

.pdf

School

University of New South Wales *

*We aren’t endorsed by this school

Course

1021

Subject

Civil Engineering

Date

Apr 3, 2024

Type

pdf

Pages

Uploaded by samuelharvey15

1. Briefly describe five (5) conditions that must be considered before selecting a suitable trench support method? (10 marks) Soil type: The type of soil whether it is extremely soft or a hard type of soil will effect what trench support method will be used. Depth of cut: How deep the excavation is, is a major factor in determining what trench support systems will be used. It is a general rule that trenches that are more than 1.2 m deep require a protective system. Water content of soil: The water content of the soil must be considered before selecting trench support methods, factors should be taken into place to consider if there is any dewatering requirements and if there is going to be long-term effects on the stability and safety of the excavation. Other operations in the area: You will need to consult with other professionals to see if the trenc support method you want to use will engage in the area's main electricity/ water lines. If there is a live electrical wire nearby, nonmetal shoring may be used. Changes due to weather or climates: If there is sudden flooding or another weather event, the trench support method that is currently being used may need to be changed or replaced. 2. Briefly discuss the challenges associated with tunneling in urban areas and suggest ways of addressing them. (10 marks) There are many potential challenges that may arise when tunneling in urban areas, such challenges include impeding on existing infrastructure in urban areas. There are networks such as gas, water, and electricity that would cause huge problems if these were impeded. The limited amount of space in urban environments also magnifies the challenges of developing tunnels, as there is a higher chance of damaging existing facilities and structures. However, due to the advance in construction technology, there are ways of addressing these issues. For example, there is teams of experienced individuals that will actively survey the urban area and investigate if there is any existing underground structures before the tunneling process begins. Furthermore, there is technology that can scan the ground ahead and alert the tunnel machine operators that there is live electricity main for example and the process can stop before this is damaged and would affect millions of individuals. 3. a. How does very hot weather affect the performance of concrete? (4 marks) Extremely hot weather can adversely affect the performance of concrete ultimately due to the increase in evaporation; this can lead to the concrete drying out and stiffening resulting in a premature finish of the concrete. Through the increased evaporation of moisture from the fresh concrete, this increases the setting time, making it harder to place the concrete effectively.

Due to the need for more water to be added to the concrete mix to maintain workability, this increases the water to cement ratio, resulting in a decrease in strength and durability. The increased rate of evaporation will cause a poor surface appearance of the concrete, there may be a color difference in the concrete b. Briefly explain any five (5) precautions that should be taken when concreting operations have to be carried out in very hot weather in order to minimise the effect of the hot temperature on the concrete performance. (10 marks) Implementing set-reatrding admixtures (Type Re) in the concrete mix to slow down the setting of the concrete, to maintain the initial moisture in the concrete mix, and to keep the concrete workable, this avoids problems such as thermal cracking and poor surface appearance. This is mainly used in large and extremely valuable concrete pours; injecting liquid nitrogen directly into the concrete mixture or truck can lower the concrete temperature and keep it workable. When transporting and working with concrete in extremely hot temperatures, all equipment used such as pump lines, conveyors, and chutes should be enclosed or shaded with reflective colour to reduce the effects of the sun. This prevents the issue of thermal cracking. Pouring concrete at night in extremely hot areas such as Dubai is extremely effective in battling the effects of increased evaporation. This will help increase the setting time and the durability of the concrete. Spraying the concrete with ‘aliphatic alcohol’ after the initial finishing of the concrete will reduce evaporation and ultimately the cracking of the concrete. 4. Mention four (4) ways of ensuring the stability of a constructed scaffold. (6 marks) Checking if the scaffold is built on solid ground: You can ensure your scaffold is stable easily by checking the density of the ground the scaffold has been erected on. Is the ground soft? Is the ground muddy? If so you must check that sole boards have been used to distribute the load properly. Checking if the scaffold is stable: An individual can easily check if the scaffold is stable just by looking at the scaffold to see if it is moving in the wind if it shakes when you move it yourself. If the scaffold is shaking a lot it is not stable.

Checking if the standards are plumb: If the standards on the scaffolds are not plumb, this is an easy indication that the constructed scaffold is unstable. However, you must always check with the installers to see if the standards are designed to be that way. Distance between standards is more than 2.5m: This is an easy way to check if the erected scaffold is a table or not. If there is more than 2.5m distance between two standards, the scaffold would be considered unstable. 5. In recent times, there have been increased drive for underground construction, including tunnel construction in urban areas. Briefly discuss five (5) reasons/factors behind this drive. (10 marks) A desire for individuals to be able to take in the natural beauty this country has to offer such as our incredible mountains, seaside views, and big trees has increased the drive for underground construction to ensure that the natural flora and fauna of the land is not disrupted, An increase in population has led to an increase in vehicles used, therefore to accommodate the increasing traffic requirements there has been a drive for underground tunnel construction this will also reduce traffic. There is also been a drastic reduction in the amount of usable surface land for construction in urban areas, therefore leading to a drive for increased underground construction. There has been an increase in construction technologies and advancements in equipment such as tunnel boring machines, therefore, making underground construction easier, therefore, leading to an increased drive. There has been an increase in people's desire for futuristic construction, and people are more open to taking leaps for example many construction companies want the label of being the first company to produce an underwater bridge etc, 6. a. Mention eight (8) factors affecting the selection of bridge construction methods. (4 marks) The scale of the bridge: The local cost of materials The local weather The local labour markets The accessibility of the site

Your preview ends here

Eager to read complete document? Join bartleby learn and gain access to the full version