From a construction perspective, the onset of winter does not automatically mean winter construction conditions. Strictly speaking, winter construction officially begins only when the average daily outdoor temperature remains below 5°C for five consecutive days. So, what issues should we pay attention to during winter construction? What measures should be taken accordingly? Here is a brief discussion: First, pay attention to personal protection. Due to low air temperatures and relative dryness in winter, the respiratory tract is more irritated, making it easier to trigger respiratory infections, nasal mucosal congestion, rhinitis, and other diseases, so clothing should be adjusted accordingly. In addition, under low-temperature conditions, muscle tissue contracts and extensibility decreases, making large movements prone to strains, and joint flexibility and coordination are relatively reduced. Therefore, before working outdoors, a certain amount of warm-up activities should be performed, such as doing gymnastics, stretching limbs, and moving joints. Cardiovascular and cerebrovascular diseases may also be adversely affected due to contraction in low-temperature environments, so attention is needed. Especially during cold waves with significant temperature drops, the body loses heat rapidly, so everyone must keep warm to prevent frostbite.
At the construction site, everyone should comply with winter construction regulations and pay attention to preventing the following issues:
1. The foundation soil within the construction area must never be soaked by water or melting snow, and ice blocks, residual snow, and other debris must not be mixed into the foundation soil or backfill.
2. During underground foundation pit construction, corresponding anti-freezing measures should also be taken for adjacent foundation soils.
3. Anti-freezing measures must be taken for the set positions of coordinate points, benchmark points, and axis positioning points within the construction area to prevent displacement due to soil frost heave, thaw settlement, and vibration, which could affect measurement accuracy.
4. During shallow foundation construction, the building foundation should be built on soil layers with the same frost heave properties and must not be placed on soil layers of different properties.
5. During shallow foundation construction, excavation of foundation trenches at all parts should be carried out simultaneously, and the thickness of residual frozen soil layers should be recorded at the four corners and middle parts of the trenches, with residual frozen soil layers of standard thickness reserved.
6. During construction, foundations at all parts should be constructed simultaneously; partial construction and partial idleness are not allowed. After construction is completed, the side soil must be backfilled in place promptly.
7. To avoid impacts on the surrounding environment, vibration prevention and isolation measures should be taken when performing dynamic compaction or pile driving on frozen soil.
8. During dynamic compaction construction, trial compaction should be conducted according to national standards to set construction technical parameters, and unauthorized violations are not allowed.
9. When performing heavy tamping, ensure that the foundation soil is in an unfrozen state. Methods such as segment-by-segment excavation and compaction can be adopted. However, for already frozen foundation soil, it must be thawed before compaction.
10. During foundation pit excavation, a certain thickness of soil layer should be reserved and removed before compaction. 11. When compacting on sandy soil, water should be added to the foundation trench, and chloride salt antifreeze must be mixed into the water; its concentration can be determined through testing based on temperature conditions.
12. It is prohibited to compact or backfill frozen soil into the bearing layer of the foundation. Backfill soil must comply with relevant quality standards.
13. If dynamic compaction is performed on cohesive or silty soil, coarse-grained materials should be spread on the surface of the compacted soil, and soil and materials adhering to the bottom of the tamper should be cleaned promptly.
14. When driving displacement piles into frozen soil, if the frozen soil layer thickness exceeds 0.5 meters, the method of drilling guide holes should be adopted, i.e., first drill a hole with a diameter 50mm smaller than the pile diameter, and then drive the pile. Of course, if convenient, directly excavating the frozen soil or locally thawing the frozen soil can also be used as a solution.