The underground construction services provided by our Group can be categorized into the following components, whereas individual engagements undertaken by our Group can comprise more than one of the following components:

1. Tunnel construction services

Tunnel construction is a branch of civil engineering concerning with the construction of underground enclosed tunnels, shafts, chambers, passageways and other related underground facilities such as railway stations and ventilation shafts. In terms of our Group’s operations, this generally relates to

(i). advanced work such as slope stabilisation around the tunnel, and the construction of shafts for transporting equipment；

(ii). the main tunnel construction works, including excavation, shotcreting and concrete lining; and；and

(iii). structural works such as the construction of ancillary buildings.

Advanced works

Advanced works in tunnel construction are mainly related to slope works, which are a type of civil engineering relating to the engineering behaviour of slopes, and using physical techniques such as soil nails to stabilise and reinforce slopes. In terms of our Group’s operations, this generally relates to the advanced works required prior to the tunnel construction and more specifically, to reinforce the slopes above the tunnel opening in a mountain, or to provide a stable working environment for cut and cover tunnel construction.

In our provision of slope works services, we mainly employ the soil nailing method which involves drilling holes on the slope, driving steel nails into the holes, and grouting concrete into the holes to stabilise the slope. We generally provide such services in conjunction with other tunnel construction-related works such as the construction of shafts as part of the preparation for the tunnel construction works.

Main tunnel construction works

Main tunnel construction works are a part of tunnel construction concerned with the construction of tunnels, and mainly consist of four stages, namely

(a). excavation of rocks and soil;

(b). stabilisation of tunnel walls;

(c). design and fabrication of tunnel shutters; and

(d). in situ concrete lining.

For excavation of rocks and soil, our Group mainly employs the drill and break or drill and blast methods to remove rocks. After the excavation, we would proceed to stabilise the exposed tunnel walls by using a method called wet shotcreting, which involves spraying a layer of concrete-like material on the tunnel walls to stabilise the tunnel structure and prevent loose rocks from falling down. We would then proceed to the design and fabrication of steel tunnel shutters, which subsequently act as a mould for the concrete lining.

Lastly, we implement in situ concrete lining, which involves pouring concrete into the lining between the shutters and the tunnel walls, forming the final structure of the tunnel and the surface of the tunnel walls.

Structural Works

Structural works are a branch of civil engineering concerned with the analysis and design of structures that support or resist loads.

In terms of our Group’s operations, this mainly relates to the construction of ancillary buildings, and permanent or temporary support structures which usually form part of a larger tunnel construction project. Our Group’s operations include, but are not limited to, the construction of ancillary buildings such as plant rooms, workshop buildings and sewage-treatment plants. To complete the construction of ancillary buildings, our Group

(a). designs and provides supporting calculations for temporary and permanent structures;

(b). provides temporary falsework as working platforms;

(c). provides temporary formwork installation services; and

(d). provides concreting services.

In terms of our Group’s operations, our tunnel construction projects may sometimes only contain one, a few, or all of the above mentioned procedures.

2. Utility construction services and others

Utility construction services are a branch of civil engineering relating to the construction and refurbishment of underground utility works including gas pipelines and electricity cables. In terms of our Group’s operations, we mainly provide underground utility construction and refurbishment services relating to underground gas pipelines.

Our Group is also engaged in the provision of other general structural and slope works apart from those mentioned under the paragraphs headed ‘‘Advanced works’’ and ‘‘Structural works’’ above. Such general structural or slope works would not be related to, or form part of, the tunnel construction projects. Our Group has been engaged by customers from both private sector and public sector on the provision of such general structural and slope works.