Risk Assessment in Deep Excavations and their Effect on Surrounding Structures : A review Syed Uzairuddin 3rd Year UG, Civil Engineering Dept. National Institute of Technology, Raipur [email protected] Abstract—Construction is crucial to a country's overall The amount and direction of the generated deformations are economic growth, particularly in developing countries, in dependent on the building's closeness to the excavations, as the current era of globalization. If construction operations shown schematically in Fig. 1. Ground movement prediction are not carried out strictly according to a local or national and management around these construction pits are critical building code, they might result in large-scale failures during the planning and construction phases of these endangering human lives, personnel property, and the excavations to protect surrounding structures from current and economic balance. It is vital to handle the construction future activities as the project progresses(El-Nahhas 2013). process's risk elements. The self weight of soil behind the retaining line is the driving force and shear strength of soil is the resisting force as a result, deep excavations invariably cause lateral and vertical ground deformations. As a result of the produced ground deformations, nearby buildings and utilities become kinetically loaded. Risks associated with ground movement cannot be calculated solely using mathematical predicting models and engineering simulations as it needs to address the uncertainty of soil properties, Geo-materials, ground constitutive nature, building stage modelling, three- dimensional impacts of deep excavations, time-dependent natures of ground deformations, and the critical necessity to include human variables such as craftsmanship into prediction models are all important considerations.This article provides an overview of risk assessment and management technologies and approaches that have been adapted for use in deep excavations. This article presents a Fig 1. Deformations Induced by deep excvations[] review of the most effective methods for evaluating hazards related with deep excavation and current mitigating techniques. Theoretical approaches to The advancement of science and technology in the enhancing the safety of deep foundation excavation are construction sector, as well as the emergence of multiple fast- examined in the context of a hospital building in growing economies throughout the world, has resulted in a Khartoum state and a residential district project in decrease in the time necessary to finish a project and an southern Jianxi province. increase in the quality of construction. The foundation of a building project is critical for determining Keywords - Deep Foundations, Risk Assessment, Globalisation the structure's stability. Extensive foundations, which are frequently used in commercial structures, need extensive I. INTRODUCTION excavations. The stability of large-scale excavation is critical The use of underground space in the development of to the project's progress. The quality of a building's foundation congested urban areas for various reasons, such as has an effect on its quality, either directly or indirectly. As a transportation tunnels, is becoming increasingly popular result, it is critical to identify and manage the hazards across the country.Parking garages, basements, and utilities associated with deep foundation construction. The soil are all underground. Many plans to use the underground were conditions and the foundations of the surrounding built highlighted by ElNahhas. Deep vertical excavations and environment have a direct effect on the stability of a subterranean tunnels are required for such ambitious projects, foundation. Risk management is the act of identifying which are frequently near to existing structurally susceptible potential hazards and mitigating or eliminating them in order buildings and utilities(El-Nahhas 2013). to maintain a specified degree of safety throughout the duration of the project(Ahmed 2015). A variety of elements, including wall stiffness, ground manifest in the work environment(fok et al 2012). It is a conditions, hydrogeological condition and control methods, continuous process and hazards can be identified in various excavation depth, construction sequences, and craftsmanship, stages of a project. can all effect excavation-induced deformations. TR26: 2010: Technical Reference for Deep Excavation serves • During design and implementation. as a reference for deep excavation design(fok et al 2004). It • Prior to important tasks. necessitates a thorough examination of the potential impacts • During activity. of deep excavations on the surrounding area, particularly • After Near Misses or Minor Events. structures near the excavation sites. This evaluation is an important aspect of the risk management process for the Different types of soil have different stress strain relationship. design of temporary excavation operations. It has been noticed in past years that many excavation slope collapse without prior warning resulting in loss of property, II. RISK MANAGEMENT PROCESS serious injury or even death. Excavations are prone to a Throughout the life cycle of a project, the risk management variety of hazards. Collapse of sides, Proximity to nearby process is a systematic means of finding, analyzing, and structures, Wall deflection more than predicted are to name a responding to risk events with the least amount of money few. spent to achieve the best or acceptable level of risk control(fok et al 2004). RISK ASSESSMENT In this phase of risk management model the identified hazards Steps involved in the Risk management process - are studied extensively on the basis of their probability of occurrence and their ramifications by studying the causes, and • Hazard Identification the magnitude of failure in the past, a risk matrix is designed. • Risk Assessment In this matrix potential hazards are categorized with respect to • Risk Control their frequency of occurrence and the severity of the accident. • Risk Monitoring They are then rated from A-D. In an Ideal situation all identified risks in a particular site should be brought down to a Because each site has distinct soil conditions and soil rating of C or D. characteristics, there is no hard and fast rule for how to implement the risk management measures. It is the expertise RISK CONTROL of designer and constructional professional to identify the This step involves taking actions to eliminate, mitigate, or potential hazards as per the given soil conditions. HAZARD IDENTIFICATION The very first step in the risk management model is Hazard prevent potential dangers, depending on their nature. Risk Identification. A hazard is any source of potential damage, avoidance may entail realigning a public/commercial structure harm or adverse health effects on something or someone(Mair, away from an existing structure during the design phase, for Taylor, Burland 1996) . Risk is the probability of a hazard to example. The risk would be eliminated by demolishing an older structure in the area. Applying steel sheet piles to support the earth excavation operation or reinforcing a Another well known failure in the history due to lack of building's foundation that may be harmed during the geotechnical knowledge is the Nicoll Highway in Singapore excavation process are examples of risk mitigation. All of (Fig. 3), which was caused by insufficient site studies, these strategies include an exhaustive study of numerous misunderstanding of findings, flaws in the bracing system alternatives, as well as the criteria for selecting the best one. design, and the use of an inappropriate technology for wall Cost, duration, and desired project function are some of the strutting by jet grouting(Whittle, Davies 2006). elements that must be considered during the selection process(Burland, Broms, De Mello 1977). As previously stated, it is a continuous process that begins with design and continues well beyond the start of construction. On a regular basis, the contractor may be needed to do additional operations (fok et al 2012). Certain precautions, such as a supervising plan or the use of correct equipment, can help reduce the risk of certain dangers to an acceptable level. RISK MONITORING Risk monitoring is an important phase of risk management model. This stage ensures that the identified and assessed risks Fig 3. Nicoll Highway failure(2004) due to nearby excavation. are maintained at an acceptable level throughout the construction process, and that the assessment is consistent as Much more common than breakdowns are serviceability issues the activities progress. The mitigation measures that must be caused by considerable foundation settling and lateral adopted during construction in order to decrease risk to deformations caused by extensive excavations(Horodecki, acceptable levels are taken and followed through until the Dembicki 2014). Due to the generated deformations, the activities are completed or the related hazards are no longer structure may face distresses such as structural or architectural present(fok et al 2012).During construction, instrumentation element fracturing, uneven flooring, or unusable windows and work is a critical component in assessing the danger of doors(Clough 1990). The quantity of acceptable deformations construction to buildings. The findings of the instrumentation and the degree of earthwork related damages are determined should be interpreted in relation to the construction