Using Shotcrete in Slope Stabilisation

Shotcrete is a versatile building material that is used in a range of construction projects. One industry that heavily relies on the use of shotcrete is in slope stabilisation, where rock mass is supported on sloping terrain to prevent any rocks from falling below. Slope stabilisation is typically required when building railway lines, highways, or dams, and despite the contractors’ best efforts to cut through the terrain so that the majority of rock mass is self-supporting, additional support in the form of shotcrete and mesh is frequently required.

The characteristics of the terrain play a pivotal role in slope stabilisation so there naturally are many factors which need to be taken into consideration. Some of these factors include the height, stability, soil composition, and gradient, along with the climate’s characteristics. The angle of repose is another vital factor which refers to the angle at which the terrain can support itself. All of these variables must be inspected closely and taken into to account together to produce a complete picture of how to address any slope stabilisation concerns.

Why use shotcrete?

There are a number of approaches used to stabilise slopes, however shotcrete has proved to be very useful due to its versatility, durability, early resistance, and its capacity to adhere to the subtract. The process of pneumatically spraying concrete at high velocity allows the concrete to compact firmly against the surface so that any holes and fissures are filled to prevent rock mass from slipping. Not only does shotcrete offer a protective coating over the slope’s surface, but it also serves as an 'anchoring surface' where rock bolts and soil nails can be attached.

Despite this, there are particular circumstances where shotcrete alone will not be enough and additional stabilisation such as fibres, rebar, and mesh are also needed. This is normally required when very steep slopes with poor rock mass quality need to be stabilised and present an increased risk of slope failure.

How is shotcrete applied?

To stop the development of pockets of material and minimise any rebound, shotcrete is usually applied from the base of the slope upwards. The same strategy is commonly witnessed when using shotcrete as ground support for mining and tunnelling. Due to safety issues with slope stabilisation, mechanised shotcrete equipment is normally used with an extensive spraying arm that can be fixed to trucks to allow greater accessibility. Mechanised shotcrete equipment is used because it enables operators to apply shotcrete from a safe distance and prevents any fallouts.

Either dry-mix or wet-mix shotcrete can be used, however the wet-mix process is normally more suitable to decrease the level of rebound. Despite this, dry-mix shotcrete is less expensive on smaller projects and on projects in isolated areas. It's also pivotal that water drainage is taken into account given that rain and water-related erosion always raise the risk of slope failure. In areas where heavy rainfall is common, it's essential that a drainage system is installed to stop the formation of water passages and build-up of water pressure on the back of the shotcrete facing.

Fibre-reinforced shotcrete

There are some circumstances where using fibre-reinforced concrete is a better alternative than using mesh or rebar as additional support. With very steep slopes, it's typically too challenging to place mesh or rebar without specialised equipment such as man lifts. Also, the type of soil or rock can make it difficult to use pins to hold mesh and rebar in place. Fibre-reinforced shotcrete has offered contractors an easy and effective solution to challenging slope stabilisation projects and is being used increasingly in the civil engineering field.

Evolution Shotcrete have years of experience in all forms of slope stabilisation techniques and have delivered some of the most challenging Road Corridor and Rail Cutting Stabilisation projects. If you're interested in safe and efficient slope stabilisation solutions for a variety of projects, talk to their staff directly on 07 5561 8885.