In the construction of roads, soft subgrade with high moisture content is often encountered.
The treatment with geotextile materials can isolate soil particles and transfer them to high-strength subgrade materials, dredge or filter out the water in the soil to prevent softening, and also share the load, so as to maintain the stability of the subgrade and smooth the next process.
In 2019, our company accepted the subgrade project of Machi branch of Baotou 210 national road. One section of K6 + 700-k8 + 700 is soft soil subgrade. When we first arrived at the construction site in April 2019, there was still water on the top surface of the ground.
If the construction is carried out in accordance with the routine, the silt shall be removed and replaced and compacted in layers. But in this way, it not only delays the construction period, but also increases the cost. Finally, the new geotextile technology is adopted.
Geotextile Mat Installation Procedure:
After the water is discharged on the silt top, the geotextile can be laid.
The adjacent two pieces are overlapped by 30cm. In case of wind, it is not suitable to pave too long. It is very simple to press them with the materials of the next process without being blown up.
Then, according to the design requirements, the subgrade auxiliary layer, such as sand, gravel, pebble, etc., shall be laid on the geotextile. The selected auxiliary layer only needs the material that can dredge the water and does not soften.
We use natural gravel and pave a layer of 30cm first. When we use bulldozer to roll, it will bounce back and forth, swell left and right, and the track will sink. But after laying the second layer.
No more bouncing, only a few other places are compacted and leveled manually, and the subgrade is basically formed. When the third layer is paved, the distance from the top surface to the geotextile is more than 80cm.
The load exerted by the roller on the geotextile is triangular. When it is transferred to the geotextile, it has been dispersed enough to bear its pressure, without sinking, deformation or elasticity, and has formed a completely qualified subgrad.
The Main Mechanisms of Geotextile Materials Are as Follows:
① due to the isolation effect of geotextile, the subgrade material is not squeezed into the soft soil foundation, and the system forms a flexible integral raft foundation, thus improving the overall strength of the soil foundation and the allowable bearing capacity of the soil foundation;
② due to the reinforcement effect of geotextile, the system is significantly higher than the strength of plain soil;
③ due to the constraint effect of geotextile on the foundation and aggregate, both increase bearing capacity is improved;
④ due to the separation effect of geotextile, fine-grained soil of subgrade is prevented from squeezing into gravel and the gravel is prevented from embedding into soil foundation;
⑤ due to its friction, boundary and membrane effects, the geotextile system changes the stress acting on the foundation and plays a significant role in preventing the settlement and horizontal displacement of the weak section.
During the construction, it should be noted that there should be firm restraint measures around the soft foundation to prevent the collapse and deformation caused by the external force. If there are practical difficulties, the laying width of nonwoven geotextile can be increased. Generally, the width of each side is 2-3m.
Features of the Project:
① the geotextile sheet system project is used to treat the soft soil foundation, which is not only complete and effective, but also simple and convenient in construction;
② the construction period is shortened, and the economic benefit is significant;
③ the soft soil does not need to be excavated and discarded in construction, which reduces the construction waste and protects the environment. Since the project was opened to traffic in 2001, no deformation has taken place in the subgrade section, and the quality has been guaranteed.
Due to the use of geotextile materials and new construction technology, not only the investment is saved, but also great economic benefits are brought into play.
At the same time, due to the convenience of the construction process, time is gained, construction period is advanced, and great social benefits are brought into play.
Geotextile fabric is used more and more widely. It plays different functions in different applications, such as isolation, seepage control, reinforcement, filtration and drainage, and protection.