Curved Microtunnel Mean?
A curved microtunnel can be defined as a microtunnel that is excavated on a curved drive. The microtunneling process has evolved over time to allow curved alignments that permit extended drive lengths by avoiding obstacles and intermediate shafts. Curved drives require guidance systems such as those used on longer bores.
Since pipe materials used in trenchless construction are rigid, the deflection is concentrated on pipe joints, and the jacking stresses are transferred across pipe joints in a curved alignment.
Boring microtunnels with tight curves is only possible with rigid, thick-walled reinforced concrete or polymer concrete jacking pipes with articulating joints.
Trenchlesspedia Explains Curved Microtunnel
A microtunneling project is curved for reasons such as when it becomes impossible to reroute the project, or when short straight drives cannot negotiate the curve, and when the social and environmental concerns demand a curved tunnel.
To complete a curved microtunnel successfully, the guidance and navigation system should be able to communicate without a glitch. The guidance system required for a curved tunnel can be a Laser Total Station System or a Gyro Navigation System.
For curved alignments, the pipe joint design is very important because the articulation is concentrated in the pipe joints. Though shorter pipe lengths reduce the joint articulation angle, it increases the number of joints. It is therefore recommended to use longer pipes unless unavoidable, and keep the number of joints to a minimum.
The joints have to provide a good seal against groundwater and soil even in the articulated state. The design of the joint therefore should be such that the area where the pressure is transferred is sealed against water and soil so that the behavior of the pressure transfer-ring is not adversely affected.