Steel casing, Qionghai manufacturer of large diameter thick-walled steel casings

In bored pile construction, steel casing is commonly used to locate the pile positions to be drilled. The casing is made of steel with a wall thickness of 10mm. When positioning the casing, first use the pile center as the center of a circle and mark the casing position on the soil based on the casing radius. After the casing is in place, apply pressure to bury it about 50cm deep. If it's difficult to push down, first excavate some soil at the hole position, then place and bury the casing underground. During the burial process, check if the casing is vertical, and if any tilt is found, correct it promptly. After the casing is buried and in place on land, backfill and compact the soil outside the casing with clay to prevent leakage around the casing. The backfill thickness should be about 40-45cm, with the top height elevated 0.4-0.6m above (water) level. The deviation of the casing position from the hole center must not exceed 50mm.

Steel casing function: It can stabilize the hole wall, prevent cave-in, isolate surface water, guide the drill bit, fix the pile position, protect the original ground, etc.

Steel casing characteristics: Generally 20-40cm larger than pile diameter, burial depth depends on soil properties, deviation in plane position not exceeding 5cm, and inclination less than 1%.

Steel casing project quantity calculation considerations:

1. In the steel casing定额, the turnover and distribution for dry placement are calculated based on the design quality of the casing, and no additional calculation is required when using the定额; for underwater placement, the定额 includes the full design quality of the casing, and the recovery amount can be used to calculate the recovery amount according to the design (usually not calculated, as the recovery cost for standard underwater casings is also substantial, akin to picking up sesame seeds while dropping watermelons).

2. Since the定额for burying steel casing in dry areas accounts for turnover amortization (scheduled for 10 amortizations), the amount is calculated based on the full design quality in water, and the recycling amount is determined according to the design specifications. Therefore, it is necessary to calculate the quantity and quality of the steel casing in both dry and water areas based on the actual water level survey (most people wouldn't be that detailed).

3. The定额 for protective sleeves already includes the consumption of materials and equipment used for burying clay or guide frames for underwater positioning, as well as ironwork and adhesives for steel or reinforced concrete sleeve joints during installation. No additional calculation is required when using the定额.

4. When constructing using island cofferdams or building islands in water, the steel casing can be buried in the dry area for calculation.

5. Steel sleeve installations in dry locations can be controlled at 2m per pile. Generally, each sleeve section is made to a length of 2m (actual length is based on requirements and can be arranged in a schedule), when burying sleeves in dry locations, the design typically requires a depth of 1.8m into the ground and 0.2m of clay compaction around it (which is already accounted for in the quota), totaling 1.8m + 0.2m = 2m.

6. When using grass bag cofferdams, the top of the steel protective tube should be elevated 0.5-1m above the cofferdam top, and the bottom should generally penetrate the original ground level. For clay soil, the depth into the ground should not be less than 2m, and for sandy soil, it should be at least 3m.

7. The inner diameter of the steel casing in water is generally 20-30cm larger than the pile diameter, and for piles with large bore diameters, it should be at least 40cm larger. The length of the casing must be calculated based on the construction plan, with the top generally 1.5-2.0m above the construction water level (this figure differs from some textbooks; it is recommended that teachers who compile textbooks visit the site more often), and the bottom should penetrate the permeable layer (within a water depth of 5m, the soil depth should generally not be less than 3m; the specific depth will be provided by the design).

8. The quantity of steel casing is calculated based on the design quality, which includes the finished product quality after processing, such as the quality of stiffeners and connecting flanges, etc. When the design does not provide the quality of the steel casing, refer to the "Highway Engineering Budget Quotas" (JTG/T B06-02-2007) Page 340 for the per-meter quality table (the data in this table is the national average level at the time of the 07 quota compilation, and the wall thickness of the current steel casing is thicker than before).

9. If the pile diameter varies, most people would interpolate calculations based on the P340 per-meter weight chart. However, this is not precise because steel casing with different inner diameters have varying wall thicknesses and actual inner diameter expansion values.

The steel casing is a hollow cylindrical barrel with both ends open, made by wrapping iron sheets around the size of the pile hole. Generally, it is 20-40cm larger than the pile diameter and the burial depth depends on the soil characteristics. The deviation in the plane position must not exceed 5cm, and the inclination must be less than 1%. It can stabilize the hole wall, prevent cave-ins, isolate surface water, guide the drill bit, fix the pile position, and protect the original ground during operations.