Risk Assessment in Deep Excavations and their Effect on Surrounding Structures : A review

—Construction is crucial to a country's overall economic growth, particularly in developing countries, in the current era of globalization. If construction operations are not carried out strictly according to a local or national building code, they might result in large-scale failures endangering human lives, personnel property, and the economic balance. It is vital to handle the construction 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 review of the most effective methods for evaluating hazards related with deep excavation and current mitigating techniques. Theoretical approaches to enhancing the safety of deep foundation excavation are examined in the context of a hospital building in Khartoum state and a residential district project in southern Jianxi province.

Performance Improvement in Pile Anchor System for Deep Foundation Excavation Using Electroosmotic Chemical Treatment

Anchoring force is vital to ensure the acceptable performance of a pile anchor system when supporting deep foundation excavation. The soft soil has several physical properties, such as low shear strength, high water content, large void ratio, and high flowability. Traditional grouting and anchoring techniques have demonstrated technical limits to deal with these soil properties in engineering projects, and accordingly, the anchoring force in the pile anchor system is difficult to meet design requirements. This paper conducted an experimental investigation on the performance improvement in a pile anchor system using the electroosmotic chemical treatment method, with an emphasis on the deep foundation application. Experimental tests and field studies were designed to enhance anchor capacity of a pile anchor system using self-designed devices. The laboratory experiments utilized a simplified anchor system in which anchors were designed as the electrodes to conduct the electroosmotic chemical treatment and consolidate the soft marine soil collected from the project site. In addition, static load tests were conducted on the tested soil to measure the anchoring force. Finally, parametric analyses were performed to investigate effects of several parameters on anchoring force in terms of the ultimate pull-out capacity of the anchor, identifying critical parameters for the field study. Based on laboratory test results, field studies were carried out in the Yingkou city. The results from field studies were compared with laboratory test results to validate feasibility of electroosmotic chemical treatment for a pile anchor system.

Impact of High-Rise Buildings Construction Process on Adjacent Tunnels

The demand for buildings constructed along subway lines is increasing, and analysis of the impact of foundation excavation and building construction on adjacent tunnels is critical. This study investigated the variation law of tunnel deformation and surrounding earth pressure on an existing tunnel resulting from deep foundation excavation and the load of buildings. Four groups of scale model tests and corresponding numerical simulation calculations were conducted in four different modes: over unloading-loading, shallow-side unloading-loading, middle-side unloading-loading, and deep-side unloading-loading, which are according to the different relative position of the foundation pit and the tunnel. The results show that when the tunnel stretches across different areas, corresponding deformation occurs owing to the different mechanical mechanisms during excavation and loading. The results can provide evidence for the further study on the impact of adjacent construction process on the tunnels.

Hybrid SWARA-COPRAS method for risk assessment in deep foundation excavation project: an iranian case study

Existing risks in deep foundation excavation projects is a major issue in developing cities. With the rapid in-crease in the number of various deep foundation and excavation projects in big cities of Iran, many accidents related to deep excavation have been reported every year. These accidents affected delay and increased cost of project implemen-tation. Therefore identification and assessment of risks of these accidents is essential. The aim of the research was to develop a framework to overcome limitations of previous approaches to assess of risks in excavation projects. According to the complexity of a problem and the inherent uncertainty, the framework adopted SWARA (Step-wise Weight As-sessment Ratio Analysis) and COPRAS (COmplex PRoportional ASsessment) methods through introducing new criteria for risk assessment. Data was collected through interview, a literature review and a questionnaire survey distributed to excavation project experts. A case study of deep foundation excavation in Shiraz was presented. The results have shown that the risks involving construction safety, unfavourable geological conditions, shortage of managerial experience, in-complete emergency plan and subsidence of ground are the most significant risks excavation projects in Shiraz. The proposed framework and the obtained results can help stakeholders of excavation projects in developing countries better to manage project risks.

Weight Analysis of Accident Factors in Deep Foundation Excavation Based on Analytic Hierarchy Process

For the past few years, great development has been achieved in deep foundation excavation. However, due to foundation excavation’s locality, individual diversity, complexity and uncertainty, the probability of accidents in foundation pit engineering tends to be greater than that in main works, and the accident rate may even reach about 20%, which makes the study on factors leading to foundation excavation accidents quite necessary and meaningful. By use of Analytic Hierarchy Process (AHP), this paper has figured out the ratio (weight) of the investigation, design, construction and other factors leading to foundation excavation accidents to the whole factor set, which is of great guiding significance to the study on prevention and treatment of foundation excavation accidents in future.