DEVELOPMENT OF EXPERT SYSTEM FOR CONTRACTUAL RISK SHARING IN TUNNEL CONSTRUCTION

Abstract

Tunnel construction is a subject involving uncertainties arising due to the geology of the rock formations, efficiency and output of the tunnelling equipment and the management conditions. The resulting cost and time overruns are due to (1) job conditions, which cannot be altered; (2) breakdowns or other holdups, over which there is no control; and (3) poor management conditions which are within the competence of the project managers. The need for undertaking a study of management factors . leading to better advance rates in tunnelling has been explained in Chapter 1. The literature available on various aspects of management factors related to the construction industry, particularly to subsurface construction, has been reviewed in Chapter 2. There are many factors that affect the management conditions during tunnel construction all of which contribute to greater advance rates of tunnelling. An opinion poll was carried out among tunnelling experts representing both the owner (government) and the contractor, regarding the relative importance of the . various management factors in tunnel excavation. The findings of the poll are reported in Chapter 3, as they apply to the three types of tunnels: (A) short tunnels, (B) long tunnels in good or poor rock, and (C) long tunnels in very poor rock or poor environment conditions. One of the factors is the sharing of risks which is unfortunately not given due importance in India. Risks in tunnel construction arise due to a variety of causes. Thrusting all the risks on any one of the parties involved in tunnel construction, namely, the owner, the engineer, the contractor, the geologist and the insurer, will lead to adverse (ii) situations culminating in costly litigation much to the detriment of the project. Equitable sharing of risks will result in a congenial atmosphere. The risk associated with a. particular action should be borne by the party who took that action. Risks in underground construction appear at all stages - right from investigations, bidding and preparation of contract documents to actual construction. Chapter 4 discusses some aspects of sharing of risks in tunnelling contracts. In Chapter 5, the utility of expert systems in construction engineering has been described. Also elaborated are the various features of the expert system shell EXSYS used in this study. In Chapter 6, an expert. system - ESSOR -- Expert System for Sharing of Risks, has been developed. to determine whether the risks have been shared equitably by the different agencies responsible for the tunnel construction. The computer program usable on a personal computer may be used by the owner and the contractor, before, during or after the construction regarding the sharing of risks. ESSOR includes 1798 knowledge-based rules in the form of IF-THEN rules utilising a computer software EXSYS - a commercially available expert system package. A conceptual model of risk sharing has been presented. The clauses or provisions in a tender/contract documpid will cilhor benefit or adversely affect the interests of the persons involved in any underground construction: government department, engineer, 'geologist and insurer all collectively termed as the owner, and the contractor. The provisions can be fed into the expert system ESSOR, which will indicate at the end whether the sharing of risks has be,,n equitable or not. 'Flv contract documents of two projects: Project A and Project n which involve tunnel construction, have been studied and the contract clauses fed into ESSOR. The results of the test runs are included. GAPS IN THE EXISTING KNOWLEDGE From a review of the literature available on construction management, the following grey areas were identified: 1. The management factors that influence tunnel advance rates in India and how they affect tunnels of different lengths and varying site conditions need to be studied, 2. The relative importance of management factors on tunnelling rates in India needs to be understood, 3. An expert system for sharing of risks in underground construction, especially tunnels is not available, 4. No guide lines are available for energy management, 5. No reports are available on management consultancy in tunnelling, 6. Causes of failure to achieve projected targets particularly in tunnels in the Himalayan region have not been documented, 7. An urgent need exists to update technology of tunnelling in India, 8. No guidelines are available to suggest a reasonable amount of pre-bid investigations desirable in the Himalayas, which are noted for their geological complexities, • 9. The type of contract best suited to all circumstances of a tunnelling project needs to be identified, 10. Documentation of causes of delays, type and duration of delays, phase of project in which delays occurred, is needed with recommendations for prevention of delays, 11. Actions to be considered by owners in an attempt to increase 'efficiency and productivity of underground construction projects need to be reported, . (iv) 12. Factors favouring management of planning, design and construction 'by a single contractor (as opposed to separate firms for design and construction management) needs to be studied, 13. Suggestions to increase productivity of team members on a tunnel project (owners, design engineers, contractors, construction managers, and construction employees) need to be reported, 14. Organisation structure for long and short tunnels needs to he examined, 15. Improvements in contracting practices which are expected to have a strong influence on decisions affecting tunnel construction need to be suggested, 16. A satisfactory procedure for sharing inflationary effects needs to be evolved, 17. The extent of disclosures of subsurface information for prospective bidders needs to be studied, and 18. The acquisition of data and their availability after completion of the project should be ensured. Of the various grey areas existing in our present knowledge, the following three areas have been covered in this study, (I) The management factors that influence tunnel advance rates and how they affect tunnels of different lengths and varying site conditions in India, (2) The relative importance of management factors in tunnelling rates in different site conditions in India, and (3) The development of an expert system for sharing of risks, in underground construction, especially tunnels.