Subgrade construction is the basic link of municipal road construction. Subgrade construction quality not only affects the whole road construction quality and road performance, but also has great influence on urban traffic and people's daily life. In municipal road engineering, it is necessary to strengthen subgrade construction, ensure the stability of subgrade and improve the quality of subgrade engineering. At present, with the rapid development of urban economy, the traffic flow increases and the construction site is relatively small, which increases the difficulty of municipal road subgrade engineering construction. Therefore, it is necessary to explore and analyze the construction technology of subgrade engineering, improve and innovate the original construction technology, and adopt reasonable construction technology for subgrade construction to improve the efficiency and quality of engineering construction.

Construction technology and quality requirements of subgrade in municipal road engineering

Subgrade construction process

First of all, we should pay attention to the preparation of subgrade construction. Secondly, the pipeline is buried in the ground according to the requirements of shallow first and then deep, and small structures are established during subgrade earthwork construction to carry out subgrade stonework and earthwork construction. Finally, the quality of subgrade engineering is checked and accepted to see whether it meets the standards of road construction. Through the above procedures, combined with the corresponding technical means, the smooth completion of subgrade engineering can be guaranteed.

Quality requirements of subgrade construction

Maintain the stability of subgrade structure. In the construction of municipal road subgrade, the integrity and stability of subgrade structure must be guaranteed to meet the requirements of road construction. Because the subgrade supports the pavement, the subgrade is stable and the pavement is stable, and the two interact. Therefore, in the process of road subgrade construction, it is necessary to increase the construction intensity, accurately construct, improve the construction efficiency and quality, and avoid serious deformation of subgrade, which will affect the use of roads. Subgrade should have strong bearing capacity. Because the traffic volume is relatively large now, the load intensity of urban roads is required to increase. Therefore, in the construction of road subgrade, it is necessary to strengthen the bearing capacity of subgrade, improve and modify the construction design scheme according to the actual construction situation, and adopt scientific and reasonable construction technology to strengthen subgrade structure. Keep the water temperature balance between the ground and underground. In subgrade construction, the stability of subgrade is affected by the action of ground and groundwater. Especially in frost-prone areas, the water temperature drops sharply and the ground freezes, which leads to the decrease of subgrade strength and road diseases. Therefore, when subgrade construction is carried out in special areas, corresponding preventive measures should be taken, subgrade construction materials should be strictly selected, and the balance of ground and underground water temperature should be maintained to ensure the quality and efficiency of subgrade construction.

Subgrade engineering construction technology mainly includes

Filling construction technology

During subgrade filling construction, the original ground should be excavated and cleaned. When the embankment filling height is higher than 80cm, the embankment base should be leveled first, and then rolled and filled. When the height of embankment fill is less than 80 cm, the original ground should be excavated and cleaned before the fill is leveled and compacted, and then the topsoil should be loosened to 30 cm. Before leveling the soil, on the basis of ensuring smooth drainage and dredging of subgrade, all soil layers on the ground should be filled evenly to ensure uniform stress of all soil layers. In order to improve the compactness of the fill around the subgrade, the fill should be greater than the corresponding standard height when filling evenly. Finally, after the filler is leveled, it is properly rolled by vibratory roller to improve the strength of subgrade.

Excavation construction technology

When choosing materials to dig, we should pay attention to digging according to strict technical standards to avoid less digging or more digging, resulting in rework or waste. The cut slope should be similar to the fill slope. If the soil quality changes during construction, it should be reported to the relevant departments in time to modify the construction scheme, so as to design a reasonable scheme and ensure the orderly construction of subgrade. During subgrade excavation, it is necessary to maintain the normal operation of drainage and dredging, pay attention to the stability of subgrade structure, and choose the top-down method for excavation. According to the local soil conditions, improve the anti-seepage awareness and ensure the reasonable arrangement of drainage. In the case of complex terrain, manual excavation can be carried out to improve the construction quality.

Roadbed protection technology

Build a protective wall. The stone gravity retaining wall is generally used in sites with good foundation, rich stones and low walls, which has a good protective effect on subgrade. After the completion of subgrade construction, wet maintenance of subgrade should be strengthened. When curing, it can be covered with soil or cloth, and a small amount of water is sprinkled on the cover, which not only strengthens the curing of corner cracks of subgrade, but also prevents the materials on the surface of subgrade from being washed away. Because the surface of subgrade is prone to drought, if there is no moisture to nourish it all the time, it will cause surface cracking, so the surface of subgrade should be kept moist within one week after completion.

Problems and solutions in subgrade construction

Meet the requirements of subgrade compaction.

In municipal road construction, if the construction method is not accurate, the compactness of subgrade can not meet the design standard, which will easily lead to the destruction of pavement and affect the performance of road. Through research, the methods to solve this problem are mainly reflected in the following aspects: (1) when filling subgrade, anti-compaction tests should be carried out on different soils to obtain accurate data, determine the relative filling methods for different soils and improve the compactness of subgrade; During subgrade construction, the slope should be checked repeatedly to ensure the uniform stress of each soil layer; The paving method is used to carry out the test, and the corresponding parameters are obtained to guide the subgrade construction, so as to ensure that the compaction degree of subgrade reaches the standard.

Keep the subgrade solid in soft soil area.

In some soft soil areas, such as paddy fields, rivers, ponds, etc., due to the influence of rain, it has been in a wet state for a long time. If the subgrade construction is not handled properly, it will cause subgrade collapse and destroy the integrity and stability of the road. Therefore, when designing the subgrade construction scheme, we should pay attention to the actual situation of the construction site, and choose stable and firm methods such as filling soil, drainage and treating silt with stones to improve the stability of subgrade structure and ensure the road quality.

Prevent unqualified fillers from being used in subgrade construction.

Due to insufficient attention to the selection of soil quality in the road subgrade filling construction, some soil with weeds, strong corrosive soil and topsoil are filled into the road subgrade, and the subgrade structure can not be uniformly stressed, resulting in different bearing strength, which can not meet the relevant standards of subgrade design, and even the subgrade collapses and is damaged, which seriously affects the road quality and hinders traffic and people's normal life. Therefore, before subgrade construction, the soil filled in the subgrade should be strictly screened to prevent the use of unqualified soil from damaging the subgrade.

To sum up, in the continuous development of urban construction, in order to meet the needs of urban construction, the quality requirements of municipal road engineering are getting higher and higher. The quality of subgrade construction has great influence on the whole highway construction project. In the construction of municipal road subgrade, scientific construction technology is the basis to determine its quality. Therefore, in the construction of municipal road subgrade engineering, it is necessary to strengthen the research of construction technology, innovate and transform the traditional construction technology according to the relevant design requirements and accumulated experience conclusions, and adopt scientific and effective construction technology to carry out subgrade construction, so as to realize the high efficiency and high quality of subgrade engineering and promote the rapid development of the whole road engineering.

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