What are the methods of improving the highway subgrade?

There are many methods, which should be determined according to the actual situation.

CFG pile method, improved soil replacement, geogrid, etc.

Such a big problem cannot be explained clearly in one or two sentences, and it takes several books to understand a little bit of it

<>1, according to the location of the junction of filling and excavation, it can be divided into: longitudinal filling and excavation junction and transverse half-excavation and half-filling, preventing uneven settlement is the main goal of subgrade treatment at the junction of filling and excavation. Longitudinal filling and excavation junction treatment:

In order to reduce the uneven settlement between the filling and excavation sections, the soil layer within 80cm of the roadbed in the excavation area is overexcavated and backfilled; At the same time, the steps are excavated along the longitudinal direction, and the width of the steps is not less than 2m. When the original ground slope is steeper than 1:5, the step should be dug for treatment, the width of the step is not less than 1m, the height of each step is not about 30cm, the bottom of the step is inclined inward with the town spike 2-4%, and the roadbed can be filled only after compaction.

2. The soil foundation (regardless of embankment or trench) must be rolled by heavy-duty rollers or equivalent rolling machinery, so as to control the optimal water content on the site for rolling. If dry soil is found, it should be sprinkled; If it is too wet and the "spring" phenomenon is found, it should be treated by digging and drying to change the soil, mixing granules and other measures.

3. Permafrost is divided into two categories: seasonal permafrost and perennial permafrost. Permafrost has higher strength and lower compressibility in the frozen state. The bearing capacity decreases sharply after melting.

The compressibility is improved, and the ground travel foundation is prone to thaw and settle, and the frost heave generated in the frozen soil is not good for the foundation. Generally, the finer the soil particles, the greater the water content, the greater the frost heave and thawing sedimentation of the soil, and vice versa. In urban roads, the frost heave amount of soil foundation is proportional to the thickness of the permafrost layer, and the uneven soil quality and compaction degree are also prone to uneven settlement.

For seasonal frozen soil, in order to prevent the pavement from being damaged due to the deformation of the subgrade frost heave, the following points should be paid attention to in the design and construction of the next journey:

1) should minimize and prevent surface water or groundwater on both sides of the road from seeping into the top of the roadbed before or during freezing, can increase the total height of the roadbed to meet the minimum fill height requirements.

2) Select the pavement structure layer material that does not occur frost heave. Understand the relationship between different pavement materials, soil foundation and freezing depth and temperature under the pavement, so that the thickness of the frozen layer of the soil foundation does not exceed a certain limit. Control the frost heave amount of the soil foundation and do not exceed the allowable value.

3) For the structure that does not meet the requirements of anti-frost heave, measures such as adjusting the thickness of the structural layer or using materials with good temperature insulation performance can be used to meet the requirements of anti-frost heave. Porous slag is a good insulation material.

4) In order to prevent uneven frost heave, the thickness of the antifreeze layer (including the pavement structure layer) should not be lower than the provisions of the standard.