1021 Final Exam

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University of New South Wales *

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1021

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Civil Engineering

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Apr 3, 2024

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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

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The time allowed for construction The obstacles to be crossed The regularity of the span lengths b. Briefly outline the steps involved in the cast in-situ balanced cantilever method of bridge construction. (6 marks) - The form travelers that consit of mainframes, guide rails, and suspended platforms are used. - The superstructure is cast in segments in traveling forms - These travling forms are supported from one end of the completed part of the superstructure, while the other end is a free cantilever. - After the concrete reaches the required strength, the form travelers are moved forward and prepared for the next segments - This process is repeated until the whole bridge is built. 7. In a hierarchical order, briefly describe measures for controlling risks arising from excavation works. (12 marks) Excavation is a task that at times is considered extremely dangerous, there are multiple risks that can arrise during excavation, including falls from one level to another, falling or dislodging earth or rock, vibration and hazardous noise and exposure to airborne contaminants such as asbestos. In order to control these risk that may arise the hierarchy orf controls is implemented. I will lest them from the most effective to the least effective. Elimination, substitution, engineering controls, administrative controls and finally PPE. Elimination: To eliminate the risk would be the most effective to control risks such as falling rocks injuring a worker. An example of eliminating the hazard during excavation would be to use a completely automated excavation system instead of human operations, but this is not all ways possible. Substitution: An example of substitution in excavation would be to use an excavator with a rock breaker instead of a person doing the excavation manually. This controls multiple risks including exposure to hazardous chemicals, falling rocks and many more, Engineering controls: Also known as isolation, installing barriers to separate pedestrians from wrecking balls, excavators and other excavation machinery would reduce the risk of a member of the public being injured or even killed. Using shoring to the sides of the excavation is also a great way to reduce the risk of ground collapse.

Administrative Controls: If there is still risk this is where administrative controls are implemented, this includes installing warning signs near the area where the excavation is taking place so people can distance themselves from the dangerous area. PPE: Finally the use of PPE such as providing workers with hard hats, hearing protection, high vis vests, and masks will reduce the risk of workers being injured, 8. Safe design and construction of piles depend on pre-construction investigation of the ground conditions; briefly describe any four (4) of these pre-construction investigations that are needed to be conducted. (8 marks) There are multiple pre-construction investigations that need to be conducted, including geotechnical investigations and preliminary site surveys. Geotechnical investigations need to be done to identify the load-bearing capacity of the soil, what the soil is made out of, what the aggregate size of the soil is. This is extremely important to ensure the surface where piling is taking place is able to support the weight of the operating equipment and any delivery trucks. The preliminary site survey is an important investigation that needs to be conducted to identify if the land is sacred to the traditional owners. If it is there may be some rituals that need to be performed on the land before construction works can begin. Investigations with the geotechnical and structural engineers need to occur to identify the size of the piles and the type of concrete that will be put into the piles. This all depends on the size of the structure that will be built. Furthermore, geotechnical investigations will reveal if there is a previous history of flooding in the chosen area; if so there must be safety measures implemented to reduce the impact on the project. 9. It is an important practice to prepare a demolition plan to collate the key information relevant to a demolition project. Mention five (5) important issues that a demolition plan must contain. (10 marks) The proposed hoardings, scaffolding, fencing and overhead sidewalk protection: The demolition plan must outline how much hoarding, scaffolding and overhead sidewalk protection will be used. It must contain information such as the width of the sidewalk protection height of the sidewalk protection. It must also contain information regarding where the temporary fencing is being placed, and appreciate permits must be obtained. The location and condition of underground essential services such as electricity, drainage and sewerage, gas and water: The demolition plan must outline the location of all essential services, these must be obtained through companies such as Sydney water, Ausgrid etc. The demolition

plan must outline where exactly these services are located and if the demolition will expose the demolition crew to these essential services. The proposed methods for handling and disposing of demolished materials: The demolition plan must outline how the demolished materials will be removed from the site, if a bobcat will be used to remove the material if a tipper truck will be assisting the demolition crew. And most importantly the demolition plan must outline what the demolition company is to do if they are exposed to asbestos/ how they will be disposing of this. Height of the building, structural system, the extent of damage: The demolition plan must specifically outline if the whole property is being demolished or only certain sections of the building. If it is only certain sections of the building, the demolition plan must outline if there are load-bearing walls, where these are located and if they are being removed. The demolition plan must accurately and represent the areas where the demolition occurs. The emergency arrangements, which should include equipment for rescue injured persons: The demolition plan should include a SWMS, or something similar to that nature that outlines the strict safety protocols implemented in the demolition process. The plan must include a detailed step-by-step process of what will occur if a worker is seriously injured or becomes trapped during the demolition process. 10. Briefly discuss five (5) factors to consider when selecting a scaffold contractor for a given construction job. Cost: As a contractor you should prepare a subcontractor pricing comparison spreadsheet, this will list out every aspect that each scaffolding contractor is going to provide and also anything they will not provide. This will then allow the contractor to analyze who is the most cost effective contractor but also includes everything that is required for the project. Current capacity: You should also consider if the contractor can meet the desired timeframe of your project when it comes to the go live date and the finish date of the project. You should consider if they can have a team ready to erect and dismantle the scaffolding according to your project program. ‘ Familiarity with the contractor: You should consider using a scaffold contractor who has been recommended to you by other industry professionals. You should consider if they are trusted and professional. Reviews: Before selecting a contractor you should analyse any reviews left on the company website/ google page. If you are unfamiliar with the company, this is a good way to assess its performance.

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Experiences with scaffolding: You should consider if the scaffolding contractor has experience in the commercial industry if that is what you are looking for, you should also see if they have performed the exact type of scaffolding work that is required.

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