台灣位處歐亞板塊和菲律賓海板塊相擠邊緣，地質年輕、地形變化多，岩層和土層剖面也都相當複雜而多元，地震、颱風、豪雨等各種天然災害無一倖免，再加上人口密集，因此在台灣從事大地工程確實是很大的挑戰。也就是說大地工程師經常要面對許多不確定因素以及由這些不確定因素所引致之風險。不過從正面來看這些難題雖是挑戰但也同時提供了地工人一展長才發揮所學之絕佳機會，誠如土壤行為學大師Prof. J. K. Mitchell在他的經典著作Fundamental of Soil Behavior 一書的緒論裡所說，由於邊界條件不易界定及材料性質不確定等，反而提供大地工程師可以用富有想像力(imaginative) 和富創意的(creative)工作態度來面對挑戰。
Space limitation often goes along with the development of a metropolis. As a result, there are increasing needs to move civil infrastructures to the underground spaces. Similar challenges encountered by the underground projects are various uncertain factors to overcome throughout the development of a project. Geotechnical engineers are required to tackle these uncertainties rationally. In recent years, “Risk Management” has emerged to become a useful tool in the face of uncertainty. This paper attempts to summarize current status and provide future outlook of risk management application on underground projects. Past failure case records are first reviewed to learn the essence of hazard events and the need of risk management. Guidelines of risk management for engineering projects have been published over the past few years. Currently, the implementation of a risk management system to a project is the main theme in this subject matter. The framework and basic components of a risk management system are introduced, and some detailed elements that require further addressed are outlined.
Underground engineering should be conducted in complex geological formation, encountering the enormous pressure from rocks, soil and groundwater inflow . Most works use high-powerful equipment, the highly potential hazards should be overcomed. Even the slightest mistake may cause caving strata, gushing, mechanical collision and other serious disaster . Safety managements are difficult due to complicated factor of disaster . This article applies the Risk Management System standards to establish the series procedure from design to construction, to minimize the potential hazards risk .By the effective management system, safely and successful completion will be anticipated.
The international state of the practice of dam safety risk management was discussed and the methods for dam safety risk analysis were investigated in this paper. Semi-Quantitative Analysis approach, named Failure Modes, Effects and Criticality Analysis (FMECA), by which the main defects or weaknesses of the dams can be explored in a systematic manner was adopted to demostrate the safety risk analysis for an earth dam in Taiwan. The approach first divides a dam system into several subsystems, then further into elements influencing the dam functions. Combination of the failure mode occurrence possibility, the detection or intervention feasibility and consequencies following the failure, the criticality value for each failure mode can be obtained. Predominant failure modes are then determined with higher criticality values. The results of FMECA can be used to reduce the dam safety risk efficiently.
A total of 209 shield tunneling construction failure factors, which include: 1. shield machine, 2.launch and arrival, 3. alignment management, 4. excavation management of earth balance type shield machine, 5. excavation management of slurry type shield machine, 6. segment, 7. backfill grouting, 8. water stop, with their general control measures are identified. Risk Priority Number of Failure Mode and Effective Analysis is adopted to evaluate risks of shield tunneling in order to recognize high-priority risk activities. General control measures of these high risk activities are reviewed throughout the process. According to the principle of the Total Quality Control System, proper actions are required based on each case condition during design and construction stages, respectively.
Uncertainties in geo-material property and modeling are often involved in the design and construction stages of geotechnical-related projects. Risks that follow the uncertainties are one of the major factors contributing the increase in cost and construction period of a project. Risk management that was introduced recently provides concepts to systematically control the engineering-related uncertainties and reduce risks to as low as reasonably practicable until a project is accomplished. This paper presents how risk management concept is installed at the early stage of project design. A design project for Taipei Metro System is used as an example, in which risk assessment is carried out for the construction methods of shield tunnels. Techniques such as event tree analysis, fault tree analysis, expert opinion method, and risk matrix are applied for the assessment, and the associated risk-reduction approaches are proposed. These results are used as references for the decision-making of construction methods and, furthermore, management policies in the construction stage.
It has been widely accepted for the use of risk management in underground engineering in many countries but it is only in a new era in Taiwan. In this paper, concepts and procedures of risk management will be introduced and its application in two examples of deep excavation and shielding tunnels will also be described. It is concluded that each project has its own risks and has to be evaluated carefully and independently. Protection measures suggested based on risk management results have to be completely implemented in the project. In addition, study of case histories and establishment of database of risks are also important. At the end, it is suggested that researches associated with risk management shall be taken in the future include (1) ground deformations induced by deep excavations and shielding tunnels; (2) influences on geotechnical risks from site investigation; (3) applicability of existent risk assessment models in Taiwan; (4) Application of the observational method and value engineering and (5) risk sharing and dispute solving in the contract.
As a result of the accumulated experiences for many years on deep cut as well as the developed and improved analysis approaches and theories, the key point of successful or failed construction is in connection with the quality of diaphragm wall, and one of the major construction items which are difficult to control is exactly the diaphragm wall construction generally applied to deep cut construction. The primary cause lies from the guide wall construction up to the water-stop grouting between the finally completed units; in addition, the constructors used to count on the similar projects or local experiences, grasp at times and identify in advance the influence of site stratum change to construction. In view of this, this article is to analyze the risk jeopardy degree during diaphragm wall construction by means of quantitative method through risk management concept, and to apply in advance the available prevention measures so as to eliminate or reduce the uncertainty risk factors in construction. Ultimately, we hereby provide a successful application demonstration to verify the correctness of the original analysis with the interpretation from design to construction for deep cut construction risk management reference.
Risk management is a technique dealing with uncertainties and corresponding risks. It has been attracted great attention worldwide in geotechnical practice after the occurrence of several severe underground accidents in recent years. In Taiwan, the Airport Link Contract IATX03 is one of the projects formally incorporating this technique into its management scheme. This article introduces fundamentals of geotechnical risk management and demonstrates the application by the case of underpinning in this project.