Technical – Cobra method｜Yasuda Engineering Co., Ltd

Technical Information

All soil compatible type, microtunneling method with slurry and mud pressure balanced. Cobra method

All soil compatible type, microtunneling method with slurry and mud pressure balanced.

The cobra method is an epoch-making microtunneling method that can be used in small shafts from ordinary soil to boulders and bedrock.
With the joint pipe, it can be installed accurately and with peace of mind even on difficult ground condition.
Furthermore, long-distance microtunneling of about 200 m is possible even on difficult ground condition.

Characteristics of Cobra method

Characteristic 1Construction method with a wide range of soil adaptation : With a high torque performance pilot head, it is possible to construct a wide range of soil condition from ordinary soil to gravel, boulders, and bedrock.
Characteristic 2Achieved miniaturization of the shaft : It is possible to launch from a 2.0m or 2.5m circular shaft, then space problems are resolved.
Characteristic 3Improved the convenience of retrieving : The TBM that can be divided into four can be retrieved from the existing manhole. Achieved an economical retrieving.
Characteristic 4Characteristic 4/ Even in harsh ground, it is possible to construct about 200m per span. (Applicable conditions apply)
Characteristic 5Compact construction method in all : Everything related to work, such as a slurry treatment plant that can be mounted on a compact car and a segmented jacking machine, is a compact space-saving design.
Characteristic 6Respond to ground problems : The joint pipe inside the jacking pipe peculiar to Cobra method supports rolling prevention and TBM extraction due to unexpected ground, high-precision construction can be performed.
Characteristic 7Depending on the soil condition, the excavation method can be selected for pipe jacking. In addition to the slurry method excavation, the structure allows the additive to be injected into the face from the cutter face, making it possible to switch to the mud pressure balanced method.
Characteristic 8Not only one-component lubricants, but also two-component lubricants can be injected according to the soil condition. By injecting a two-component lubricant, the accuracy of the jacking pipe can be maintained and stabilized.

For details, please check the Cobra method website.