Keywords: fuzzy set, fuzzy logic, grouting, personnel safety, tunnel construction.

The main purpose of grouting in tunnel construction is to prevent water inflow at the shaft and to strengthen and solidify the ring shape of the tunnel by stabilizing the material above and behind the concrete rings of the tunnel. The grouting method and technique varies according to the structure of the tunnel, the soil, and other material surrounding and supporting the tunnel. In the case of shallow tunnels, the majority of grouting works takes place from the ground surface, as opposed to deep tunnels where grouting is performed from the inside of the tunnel. As a result, different patterns of grout are established for both cases. However, when grouting is to be performed inside the tunnel, additional safety measurements and precautions should be considered, primarily due to zone conflict with other running activities. These activities include boring, extracting the muck, and installing concrete rings.

In this paper the authors focus on safety assessment of tunnel grouting, whose basic operations depend on the four main factors:

1. Machine and equipment: Site conditions, including accessibility and material type are key factors in determining the type machine and equipment employed.
2. Grouting materials: The grout material contains chemical products that are classified as toxic or hazardous that can adversely affect workers' general health. These materials should be handled with special care.
3. Grout location: Grout holes can be drilled from the inside or outside of the tunnel; however, grouting from the inside of the tunnel requires more movement restriction and tighter health considerations.
4. Housekeeping: To maintain a safe and clean environment for the workers housekeeping is required. In so doing, the number of enabling or triggering causes can be reduced.

Safety assessment associated with grouting operations is often determined through the use of subjective judgment and personal opinion. These judgments are often articulated through the use of linguistic expressions which are not easily defined. For this reason, the authors use the fuzzy set concept as a tool to assess such safety. A rotational fuzzy logic model which involves the use of ramp functions having both positive and negative characteristics is introduced in this paper. The graphical model is presented for use to determine the performance and safety of a grouting operation.

The nature of the project requires daily inspection on grouting activities and all related items including machines and equipment to ensure continuous progress and a safe path for the tunnel boring machine. The monitoring system can be used with the help of the software based on a given condition on site. For example, the condition states that if the grouting performance is good then the safety of grouting operation is safe, but what if the real case on site is that the grouting performance is very good, or very poor, then the question arises as to how safe is the tunnel grouting operation? By applying the MPD operations the inspector will be able to find the safety value of a certain tunnel grouting operation.

The expected result of this study is a computer model that can be used to simulate the safety assessment of a grouting activity during tunnel construction. The potential benefits of this tool are multifold: (1) users can use their subjective opinion to monitor grouting operations, (2) they can also employ this tool as a quality control model, and (3) when using this tool, they do not need to understand the underlying concept of fuzzy logic which is often complex in nature.

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