Common diseases of highway subgrade and preventive measures?

Nowadays, with the rapid development of the national economy, in order to create a comfortable and smooth traffic environment for the society, all builders on the traffic front do their best to ensure the smooth flow of roads, and road traffic plays an important role in today's society. However, due to the increasing traffic volume and the influence of climate and other factors, the subgrade of many sections has been damaged to varying degrees, which not only increases the maintenance cost of the highway, but also greatly shortens the service life of the highway and increases the difficulty of treatment.

1 Common diseases of highway subgrade

Bump at bridgehead 1. 1, subgrade compaction is insufficient.

Bump at the bridgehead of subgrade and pavement is a very serious form of longitudinal deformation, which is usually caused by pavement settlement. The main reason is that the fill at the bridge head is thick, while the bridge head is rigid, and its settlement is relatively small, so there will be relatively large settlement at the part connected with subgrade and pavement, and there will be the problem of staggered platform height difference. When the subgrade is not compacted, plus the depth of water accumulated on the pavement, it will lead to the problem of longitudinal cracks on the pavement.

1.2 Slope collapse

Slope collapse is also a common disease in highway subgrade, which can be divided into landslide and slip according to different soil types, failure reasons and scales. Landslides are mainly caused by insufficient soil stability, such as steep slope of highway subgrade, exposed toe of slope or improper arrangement of fill height. Slip is mainly caused by the downward movement of a small amount of geotechnical slope and the downward sliding of thin soil on the slope surface, which is mainly caused by running water scouring the slope or improper construction.

1.3 subgrade settlement

Highway subgrade settlement refers to the vertical settlement of subgrade surface, and this settlement is usually irreversible. Subgrade settlement is an irreversible common disease, and it is also the most common disease among subgrade diseases.

There are many reasons for subgrade settlement, mainly caused by foundation and self-compression settlement. Foundation settlement refers to the existence of soft soil, swamp or loose soil on the original natural ground, and its bearing capacity is extremely low. Without treatment before subgrade construction, under the action of subgrade self-weight, the subgrade sinks or both sides are squeezed out, resulting in subgrade sinking. Subgrade settlement is caused by improper selection of subgrade filler, unreasonable filling method, insufficient compaction and formation of over-wet interlayer inside subgrade embankment. Under the combined action of load and water temperature, subgrade deformation and vertical displacement occur.

1.4 crash and fragmentation

Collapse and debris are also common in highway subgrade, mainly because the slope of cutting makes the rock surface different. Under the alternating action of atmospheric humidity and temperature, and under the action of rain erosion, the surface rocks peel off from the slope and roll down. When a large rock is separated from the slope surface, it can be called collapse. These debris are accumulated in the side ditch of highway cutting, which has a great influence on the drainage of the side ditch. When the drainage of cutting section is not smooth enough, it may cause other pavement diseases.

2 subgrade quality objectives and requirements

2. 1 The subgrade should have sufficient overall stability.

Subgrade is built by directly filling or excavating a part of the ground. After subgrade construction, the natural balance of the original ground has been changed. In areas with poor engineering geology, the construction of subgrade may aggravate the unbalanced state of the original ground, thus leading to various damage phenomena of subgrade. Therefore, in order to prevent the overall deformation or damage of subgrade structure under the action of traffic load and natural factors, certain measures must be taken according to local conditions to ensure the stability of subgrade overall structure.

2.2 The subgrade should have sufficient strength.

Subgrade strength refers to the ability of subgrade to resist deformation and damage under traffic load. Due to the traffic load and the self-weight of subgrade and pavement, the lower part of subgrade and foundation are deformed to some extent, and the larger deformation will affect the service quality of pavement. In particular, uneven settlement directly leads to uneven settlement of pavement, which reduces the smoothness of pavement and is also an important reason for early damage of pavement. In order to ensure that the subgrade does not deform beyond the allowable range under the action of external force, it is required that the subgrade has sufficient strength.

2.3 Subgrade should have sufficient water temperature stability.

The water temperature stability of subgrade refers to the ability of subgrade to maintain its strength under the action of water and temperature. Under the action of surface water and groundwater, the strength of subgrade will be significantly reduced. Therefore, for subgrade, it is not only required to have sufficient strength, but also to ensure that the strength will not be significantly reduced under the most unfavorable water temperature conditions. This requires the subgrade to have certain water temperature stability.

3 subgrade disease prevention measures

3. 1 Carry out subgrade construction in strict accordance with subgrade construction requirements.

3. 1. 1 Select appropriate filler and do a good job of compaction.

In the process of subgrade filling, subgrade fillers with good stability, high hardness and good solidification should be selected, such as sand and gravel. In the process of construction, we should mainly deal with the stability of subgrade filler, adopt reasonable construction methods and strictly abide by the requirements of highway subgrade construction specifications. After selecting the filler, in the process of compaction, the method of layered compaction should be adopted to ensure the compactness of each layer of filler in the subgrade, so that the subgrade can have enough strength, compactness and stability to withstand the load of vehicles and the damage of natural disasters [2].

3. 1.2 Control subgrade water content.

In the process of subgrade filling, it is necessary to control the moisture content of subgrade, otherwise, weak interlayer will be formed between layers, which will affect the strength and stability of subgrade and also bring some influence to the compaction of subgrade. In this respect, when cohesive soil with high water content and low natural consistency is used as subgrade filler, the properties of subgrade filler can be changed by adding quicklime, and the subgrade can be solidified through the water absorption of lime. It can also be mixed with bentonite, super absorbent resin and other materials.

3.2 Slope protection

There are generally two ways of slope protection, namely slope protection and slope protection, as follows:

3.2. 1 slope protection

The main purpose of slope protection is to prevent surface water erosion and rock weathering and peeling. The common slope protection measures are mainly vegetation fixation, that is, planting corresponding vegetation in concrete or stone frames such as square, prismatic and M-shaped to solidify the slope and prevent sliding [3].

slope protection

Slope protection is the most commonly used form of subgrade slope protection at present. Pave (mortar or dry masonry) flaky, rubble or precast concrete blocks on stable slopes to prevent surface runoff or slope water from scouring the slopes. In general, the laying method is mortar. When the erosion is slight, the embankment on soft soil foundation can be protected by dry masonry to adapt to subgrade deformation caused by uneven settlement of foundation.

3.3 Treatment of Special Foundation

Soft soil foundation is extremely destructive, but in a broad sense, as long as external load will cause harmful excessive deformation and insufficient strength, should it be regarded as soft soil foundation treatment? In this case, it can be generally divided into two types according to the treatment location: foundation treatment and embankment treatment [4]?

3.4 Take measures to reduce weight

When the sliding surface is not deep, the sliding body is steep and gentle, and there is a certain hillside outside the landslide range, and the landslide cannot develop upwards, the weight can be reduced on the upper part of the landslide to reduce the sliding force of the landslide, which is an economical and simple control measure. The weight-reducing soil accumulated at the toe of the slope can increase the anti-sliding force of the toe of the slope, and the effect is better.

3.5 Improve drainage facilities

The subgrade design must be based on local conditions, overall consideration and comprehensive consideration, and the longitudinal and transverse drainage design of subgrade should be carried out to avoid the subgrade being soaked by accumulated water on both sides of subgrade for a long time, which will lead to the reduction of subgrade bearing capacity and further settlement and deformation? In order to keep the subgrade dry and stable for a long time, it is necessary to intercept the surface water that affects the subgrade temperature and discharge it out of the subgrade range to avoid overflow? Accumulation and infiltration [5]?

Subgrade disease is a serious obstacle to road safety. At present, we can't completely solve the problem of highway subgrade diseases, but we should minimize the harm as much as possible? From the beginning of design, we should investigate, experiment and explore the problems that have been found. I believe that scientific design and construction will cure the disease?

For more information about project/service/procurement bidding, and to improve the winning rate, please click on the bottom of official website Customer Service for free consultation:/#/? source=bdzd