Hi, need to submit a 2000 words paper on the topic Construction Techniques and Materials in the A3 Hindhead Tunnel Project.

Hi, need to submit a 2000 words paper on the topic Construction Techniques and Materials in the A3 Hindhead Tunnel Project. Balfour Beatty was awarded the construction of the tunnel which began in January 2007 with tunnelling works proceeding in February 2008. Tunnel bores broke through in 26 February 2009 and tunnel services are expected to be available in 2011.

This paper investigates the design and construction used on the A3 Hindhead tunnel with focus on the functionalities and economic considerations of the techniques and materials used for the tunnelling such as ground supports, waterproofing system and fire-resistance used in the boring substructure.

Geological mapping indicates that the Hindhead area comprises of sequences of sedimentary deposits with the tunnel to go through the 90 meters thick Hythe Beds described as highly glauconitic, cross-bedded and variably sorted sand and sandstone layers. The Hythe beds are divided into 6 lithostratigraphic layers but the tunnel will pass only through 4 of them. The tunnel layout is also designed to be above the observed historical water table with only one location where the maximum water table conditions exceed the invert level.&nbsp.

Geotechnical investigations using the shear box test and pressure meter was preferred over sonic testing and triaxial testing as the latter two either overestimate or underestimate the Elastic Modulus of the rock mass. The layers of the earth on which the tunnel will pass through have UCS classification of 2 to 5 MPa. Other properties were determined and are presented in the following:

The two tunnels were identical in design with cross passages at 100-meter nominal centres. There were two lanes per bore and were 3.65 meters wide each with full batter curbs. 1.2 meter wide verges were also provided on each side of the tunnel to provide sightlines restricted by the horizontal curvature of the tunnel and to also serve as emergency points wide enough for wheelchair access. The vertical clearance was 5.03 meters with an additional 250 mm for monitoring and other equipment.

For drainage, a continuous system was placed beneath the curb. Cable duct banks, fire main and pump main were also buried under the carriageway. Ventilation fans, lighting and communication systems were placed overhead.