In trenchless projects, power bushings, communication bushings, etc. generally use AD PE pipes as the main pipes for laying, and the tensile and compressive strength of such pipes is low. During the construction process, pipe back-dragging and flat deformation often occurs. The problems in trenchless construction can be summarized as follows:

First, there are no holes in the sand layer, and forced back-dragging leads to pipe breaking or flat deformation

1. Performance of working conditions:

① No mud discharge from the unearthed pit and the soil entry pit;

② The mud returned from the unearthed pit and the soil entry pit is clean water;

③ The mud returned and the mud entered have not changed much, that is, the mud has not carried the drilling slag and discharged;

④ The rotary torque of the drilling rig and the pull force of the feed-in pullback continue to be at a high level (small drilling rigs generally > 12MPa).

2. Reasons;

① The sand layer is not easy to form holes, and the formation is not compressible;

② The reaming in the sand layer is easier, and the speed is faster. There is more drilling slag per unit time;

③ The performance of the mud is not enough to meet the construction conditions;

The pump volume and the reaming speed do not match.

3. Solution:

① perfect mud mixing system, such formation mud does not mix well can not ensure construction safety;

② mud mixing system at least includes mud mixing and mud storage;

③ reduce the drilling speed or increase the amount of mud pump, so that the two match;

④ improve mud performance, first ensure mud performance and carrying performance;

II. Strong weathering formation drilling slag is not discharged, the hole space is insufficient

1. Performance:

① unearthed pit and into the pit without mud discharge, mud leakage;

② unearthed pit and into the pit return mud is clean water;

③ return mud and into the mud without much change that is, the mud does not carry the drilling slag discharge;

④ return slurry with small slag particles, large particles of drilling slag basically no;

⑤ drilling rig rotary torque and feed pullback pull force continues to be high.

2. Reasons:

① strong weathered formation fractures develop, resulting in mud leakage;

② strong weathered formation is easy to break, large diameter particle slag drilling content is high;

③ mud performance does not meet the construction conditions;

3. Solution:

① If the mud leakage needs to take plugging measures, the specific method is to add plugging inert materials in the mud, such as crushed newspapers, crushed plant debris, etc.;

② Improve the performance of the mud, so that it can carry the larger diameter particles Drilling slag outside the discharge hole;

3. The clay expansion pore size in the clay layer is reduced

1. Working conditions:

① The unearthed pit and the soil pit do not return slurry, and the slurry is produced along the way;

② Drill pipe and reamer adhere to very thick clay;

③ Drilling torque and feed pullback pull force continue to be at a high level

2. Reasons:

① clay layer belongs to water-sensitive strata, clay in contact with water expansion caused by the hydration of the clay block under cutting to produce greater viscosity;

② clay in the depths of the hole wall swells in contact with water and shrinks the pore size;

③ The clay block under cutting is not minced and scattered due to reaming too fast.

4. Dragging back or reaming too fast

1. Reason

Reaming too fast The hole collapses and the drilling slag is buried, resulting in the pipe pulling flat

2. Solution

① Reduce the speed of reaming and pulling the pipe;

② Increase the pump volume, so that the pump volume matches the speed of reaming and pulling the pipe;

Source: Hubei AD Building Materials Co., Ltd., welcome to share! Wuhan PE towing pipe construction consultation hotline: 17399989993