Notice of RetractionRisk analysis of shield tunnel segment failure based on Fuzzy Fault Tree method
Through analyzing and summarizing the types of shield tunnel segment failure and the relevant causes of the accident, Fuzzy Fault Tree Analysis (FTA) was employed to study the failure risk of segment and the Fuzzy Fault Tree system model of segment and segment-related systems were established. The potential failure modes of risk accidents and their influencing factors were discussed through qualitative and quantitative analysis. With its application on practical project, some effective control measures were proposed. This research could be valuable reference for the design, construction and control of shield tunnel segments.
Tunnelling through a frequently changing and mixed ground : a case history in Singapore
The Kranji tunnel is part of the Deep Tunnel Sewerage System in Singapore. It is approximately 12.6 km in length. Along the tunnel alignment, all the ground is composed of granite with different weathering grades (from fresh rock to residual soil). The changing ground from hard rock to mixed face and soft ground (and vice versa) at the tunnel level was anticipated. The tunnel depth along the route is between 15 m and 50 m. Two EPB TBMs were deployed at this tunnel with a bored diameter 4.90 m. These machines were designed so that both hard rock and soft ground could be excavated. The cutter head was equipped with a combination of both rippers and disc cutters. During the excavation, it was found that the frequency of the ground change between hard rock and residual soil is much higher than that expected. Due to the frequently changing ground, correspondingly the tunnel boring machine (TBM) operation mode had to be transferred frequently from hard rock tunnelling to transition mode and to earth pressure balance (EPB) close mode. It resulted in great difficulties for the TBM in an optimized operation condition. These difficulties included high cutter wear and flat cutters, tunnel face instability, water inflow at weathering interface, and time delays. In order to overcome these problems and speed up the tunnelling progress, the TBM used in the north drive was modified to attempt the frequently changing ground. The performance of the modified TBM was highly improved. However, the highly abrasive and frequently changing mixed face ground still caused high cutter wear, especially flat cutter wear. These posed many challenges to the equipment and the tunnel crew.
Realist Review of Programs, Policies, and Interventions to Enhance the Social, Emotional, and Spiritual Well-Being of Aboriginal and Torres Strait Islander Young People Living in Out-of-Home Care
The child protection system in Australia includes out-of-home care (OoHC) for children and young people at risk of harm and neglect. In Australia, Aboriginal and Torres Strait Islander children and young people are 9 times more likely to be placed in care than non-Aboriginal young people (Australian Institute of Health and Welfare, 2015). Australia’s history of colonization and subsequent policies have caused trauma to individuals, families, and communities and resulted in poor physical and mental health and mistrust of services. This review was undertaken to identify programs and policies currently in place that aim to improve the mental health and well-being of this vulnerable population. It provides an analysis of both the strengths of the current system as well as what has been inadequately addressed based on literature in the area.By incorporating an Aboriginal perspective, this review focuses on social, emotional, and spiritual well-being (SESWB) and the aspects of a child’s life and community that promote this. A realist review of the academic and grey literature was conducted in 2014. It included an extensive search of government and non-government (NGO) publications. The review identified nine programs or policies that are designed to improve the SESWB of Aboriginal young people in OoHC in local and international settings. These are the Aboriginal and Torres Strait Islander Child Placement Principle, cultural support plans, Aboriginal Community Controlled Organisations (ACCOs), family group decision-making, therapeutic care, and Panyappi Mentoring Program. Given that culturally competent service provision is important to SESWB, the review concludes that an increase in monitoring and evaluation is necessary to determine the effectiveness of programs and ensure their implementation and sustainability when warranted. Policy and research work is needed to adapt and devise programs promoting the SESWB of Aboriginal young people (at both the individual and system levels), determine their effectiveness, and ensure they are sustained when warranted.