A brief discussion on the construction measures for excessively wet soil during roadbed construction?

The following are the construction measures for wet soil during roadbed construction brought to you by Zhongda Consulting for your reference.

1. Characteristics of excessively wet soil

In highway construction, some borrow pits used along the line are silty and weakly expanded clay, and their plasticity index, liquid limit index, The natural moisture content is high, the water permeability is small, the hygroscopicity is high, and it is easy to lose stability. The moisture content must be controlled at about 11 to 15%, otherwise it will easily turn over during rolling. This soil is muddy on rainy days, and the clay surface dries out on sunny days, but the water content in the soil layer is as high as about 30%. Therefore, when this type of soil is used for roadbed construction, it needs to be mixed, dried, crushed, and even mixed with a certain proportion of Lime to reduce its moisture content and improve compaction characteristics. Therefore, when filling the roadbed, it needs to be turned over repeatedly, sometimes as many as 5 to 6 times, which brings considerable difficulty to the construction and also affects the construction progress.

2. Measures to be taken during construction of excessively wet soil

1. Selection and treatment of soil field Since the groundwater level of the soil field in the road section is relatively high, the moisture content of the soil is particularly large. In order to reduce the moisture content of the soil, ditches are first dug around the borrow pit to release water, and then a bulldozer is used to push the soil into a large pile and dry it so that the soil can be directly transported to the roadbed for use as fill soil. In order to ensure normal transportation after rain, the access roads in and out of the earth pit must also be carefully repaired.

2. When filling the roadbed, the thickness of the loose paving should not be greater than 30cm. Each layer must be plowed and crushed until the fill soil has a uniform moisture content and the particles meet the specifications before leveling and grinding can be carried out. Press to the specified compaction degree. Road sections that have passed the acceptance inspection should not be left for a long time. They should be filled with soil in time to avoid exposure to the sun and rain to avoid unnecessary rework.

3. Since over-wet soil has a high natural water content, and its water content will increase after rain, the optimal water content must be strictly controlled during construction. During construction in high-temperature seasons, over-wet soil will The outside is easier to dry after being exposed to the sun, but the moisture content inside is still very high. When a rotary tiller is used to turn and crush the inner layer of wet soil, the outer layer of soil is also dried together and becomes dry soil again, with a moisture content less than the optimal content. The amount of water is not easy to press to the specified density. Therefore, before the backfill soil is put on the roadbed, it should be turned and pulverized off-site until the moisture content is uniform and greater than about 2% of the optimal moisture content before backfilling. This way, less mixing can be achieved. Or without adding lime, it can not only achieve the specified compaction degree, but also simplify the construction procedures. When the natural moisture content of over-wet soil is relatively low in seasons with higher temperatures, a plow can be used to loosen the soil, and a road roller can be used to compact the soil to the required density. However, the working surface should not be too long. It should be filled with soil, leveled, and rolled to prevent water loss.

4. The over-wet soil has too much water content. It can be dug out from the borrow pit, and then piled next to the pit to dry for the first time, and then transported to the construction section for paving; or it can be dug out from the borrow pit and then Transport it to one side of the working section, and then push it to the working section with a bulldozer after preliminary drying, crush it 1-2 times with the above-mentioned machinery, and after leveling, spread all or 2/3 of the specified dosage of external admixtures evenly on. The ash mixing, crushing, mixing and preliminary rolling processes must be completed within the same day.

5. After stuffing the initially rolled soil layer for 24-28 hours, spread the remaining 1/3 lime evenly on the soil layer, then stir it, and measure the moisture content of the lime soil. , level it to the optimum moisture content of ±2% and then roll it with a heavy-duty roller until it reaches the specified density.

6. If it rains during construction, it is generally advisable to press and seal the lower soil with the upper layer of soil. At the same time, it is necessary to strengthen the drainage function, and use rainproof cloth as a temporary torrent on the roadbed slope to prevent the slope from being washed away by heavy rain. For already formed road sections, in order to prevent rainwater from seeping into the soil base, use J rainproof cloth to cover the entire road before it rains. After the rain has passed, open the rainproof cloth, perform necessary re-pressure, and re-test the compaction degree. Only after passing the standard can the next construction process be carried out. In this way, the compaction of the roadbed can be ensured and the construction period can be shortened.

7. For road sections that have been mixed with lime and cannot be leveled and rolled in the future, they must be pressed when it rains. At the same time, it is advisable to cover them with rainproof cloth. Because the road sections are uneven, rainwater may partially seep into the section. , after the rain stops, the rainproof cloth should be opened immediately and partial drying should be carried out. In some places with serious water accumulation, the wet soil can be dug out and replaced with mixed and even lime soil, and then leveled and rolled until the density is qualified.

8. For road sections that are pressed against rain and do not use rainproof cloth, they must be plowed in one direction with a crawler vehicle after the rain stops. It is not suitable to directly use a rotary tiller to crush and dry them because the wet soil sticks to them. , wrap the rotary cutter, and the broken soil blocks form a dense cover, making it difficult to remove water from the lower soil. However, when using a tractor with a plow, the soil blocks are larger, the gaps between the soil blocks are also large, and the air can circulate, which is convenient for reducing the water content. Rotary tillage makes the moisture content of the soil uniform and facilitates compaction.

9. For the filling of the "Nine-Five Area", in order to improve the strength of the roadbed and ensure the overall strength and service life of the road, reinforcement treatment is required. The method is: fill the "Nine-Five Area" with 80cm thick soil. The construction is divided into four layers, each layer is 20cm. The first two layers are mixed with 5% lime, and the last two layers are mixed with 8% lime. This not only treats the excessively wet soil, but also improves the strength of the roadbed.

3. Matters that should be paid attention to when dealing with excessively wet soil

1. When constructing excessively wet soil, the focus should be on the continuity of the construction process, seizing time, conducting surprise attacks, and often Pay attention to the weather forecast and try to avoid rain.

2. For road sections treated with lime, the lime should be fully digested and sieved before use, but the lime should not be piled for too long, especially if it is not covered, as its effective calcium and magnesium content is large. The amplitude decreases and the expected effect cannot be achieved after blending. Lime that originally meets the quality requirements can be reduced to non-standard quality if it is stored without covering for several months. ?Lime must be fully digested and strictly sieved before use, so that less lime that is not fully digested is used to treat the roadbed. After rolling and molding, when exposed to rain, the insufficiently digested lime will continue to digest, which will cause local swelling and bulging, forming Mushroom shape, affecting the strength and smoothness of the roadbed.

3. Control of moisture content of excessively wet soil. Since the natural moisture content of over-wet soil is more than 30%, and its water content will increase after rain, the optimal water content must be strictly controlled during construction. During construction in high-temperature seasons, the surface of over-wet soil will quickly dry out and become dry. , and the moisture content of the soil inside is still very high. When a rotary tiller is used to plow and crush the inner layer of wet soil, the outer layer of soil will also be dried together and become dry soil again. The water content is less than the optimal water content and it is not easy to press it to the required density. Therefore, it should be backfilled Before the soil is put on the roadbed, it should be plowed and pulverized off-site until the moisture content is uniform and about 2% greater than the optimal moisture content before backfilling. This way, less or no ash can be mixed, and it can also reduce the formation of soil clods. Granular pockmarked surface. In this way, the specified compaction degree can be achieved and the construction procedures can be simplified.

4. Since over-wet soil has a high natural water content, and its water content will increase after rain, the optimal water content must be strictly controlled during construction. During construction in high-temperature seasons, over-wet soil will The outside is easier to dry after being exposed to the sun, but the moisture content inside is still very high. When a rotary tiller is used to turn and crush the inner layer of wet soil, the outer layer of soil is also dried together and becomes dry soil again, with a moisture content less than the optimal content. The amount of water is not easy to press to the specified density. Therefore, before the backfill soil is put on the roadbed, it should be turned over and pulverized off-site until the moisture content is uniform and greater than about 2% of the optimal moisture content before backfilling. This way, less mixing can be achieved. Or without adding lime, it can not only achieve the specified compaction degree, but also simplify the construction procedures.

5. Due to the high water content of over-wet soil, the filling thickness should be strictly controlled. The number of over-thinning processes increases, which wastes labor and mechanical shifts, and also affects the construction period. Filling that is too thick cannot be plowed through. Rotary tillers are more difficult to crush. Since the moisture in the subsoil has not been lost, even if it is rolled again, it cannot meet the compaction requirements. When repeated rolling with a heavy-duty roller, the roadbed will form a "spring" state, making the roadbed unable to be stable and unable to continue construction. In the end, it can only be reworked and reworked. Do. Therefore, the thickness of subgrade fill should be strictly controlled during construction in excessively wet soil.

IV. Conclusion

Through the construction of wet soil roadbed, we explored and practiced some rough treatment measures, that is, no lime should be added when filling in high temperatures and sunny days. , but should be carried out preliminary drying treatment off-site before putting on the roadbed. When the moisture content is high and the drying period is long, the required amount of lime (5% to 10%) can be calculated based on the actual moisture content, and then the fully digested and screened lime is laid on the filled road section. After mixing evenly, it can effectively reduce the water content and improve the strength of the roadbed. Taking the above measures will not only speed up the progress of the project, but also ensure the quality of roadbed construction. The above measures can be used for reference in the construction of similar projects in the future. In future project construction, we still need to constantly discover problems, constantly explore and solve problems, ensure project quality, and build excellent projects.

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