The following is the relevant content brought to you by Zhongda Consulting on the safe construction technical measures of manually dug holes and cast-in-place concrete piles for your reference.
Manually dug holes for cast-in-place concrete piles are made by manually digging soil into holes, pouring concrete and pounding them into piles; enlarging the diameter at the bottom of the manually dug hole piles is called artificially dug hole-enlarged bottom piles. This type of pile is widely used in various places due to its reliable stress performance, no need for large machinery and equipment, simple construction and operation technology, direct inspection of the rock and soil conditions at the bottom of the pile, high single pile bearing capacity, and no environmental pollution. The disadvantages of manually digging piles are that the labor intensity of digging holes is high, the construction speed of single piles is slow, and especially the safety is poor. Based on my engineering practice, the following will describe common safety accidents and various safety technical measures in the construction of manually dug piles.
1. Common safety accidents of dug piles
Common safety accidents of manually dug piles include stones or debris falling into the hole and injuring the construction workers in the hole. personnel; operators at the hole are poisoned by harmful underground gases and become comatose or even die; the hole wall collapses due to improper support, injuring or even burying the operator alive; the cables and wires in the hole are worn and dampened, causing workers to be electrocuted and injured; a sudden surge of water in the deep hole submerges the operator, etc. wait. Practice has proved that as long as construction personnel establish safety awareness, strengthen safety education, make safety technical briefings, and put various safety technical measures in place, these common safety accidents of manually dug piles can be completely avoided.
2. Measures for protecting the openings
A concrete retaining ring must be poured around the opening, and a fence should be set up on the retaining ring, which should be 0.8m above the ground, as shown in Figure 1 shown. When working in the hole, someone must supervise the hole. The excavated earth should be transported away from the hole in time and should not be piled within 1m around the hole. Tools and people should not be placed on the concrete enclosure. Workers working in the hole must wear safety helmets and safety belts. Under special circumstances, they should also wear gas and dust masks. When using buckets to transport soil, corresponding precautions must be taken to prevent falling objects from injuring people. When using electric hoists to transport soil, their safe lifting capabilities must be tested before being put into operation. During construction, the integrity of the vertical transportation equipment and the condition of the hole walls should be checked at any time.
3. Poison prevention measures in the hole
Special underground formations often contain CO, SO1, H1S or other toxic gases, so the gas in the pile hole must be checked before each hole is drilled. Sampling testing (quick detection tubes can be used), if it is found that the harmful gas content exceeds the allowable value, the harmful gas should be removed to the hygienic standard of the minimum allowable concentration of chemical poisons, and sufficient safety and health precautions should be taken, such as setting up special equipment to ventilate the holes Ventilation (ventilation volume not less than 15L/S) and other measures to prevent acute poisoning accidents. Once an accident such as poisoning or suffocation occurs during manual digging operations, rescue must be carried out on site in accordance with the emergency measures specifications, and timely sent to the hospital for further rescue treatment according to the situation, and reported to the local construction administrative department and labor and health departments so that corresponding measures can be taken .
4. Measures to prevent electric shock
The installation and removal of all power supplies and circuits at the construction site must be operated by certified electricians. Electrical equipment must be strictly grounded or connected to zero protection and installed with leakage protectors. The electricity used in each pile hole must be disconnected. It is strictly prohibited to use one gate for multiple purposes. Cables above the hole must be elevated above 1.0m and are strictly prohibited from being mopped and buried in the soil. Cables and wires in the hole must be sheathed and protected against wear, moisture, and breakage. The lighting inside the hole should use a safety miner's lamp or a safety lamp below 11V. Operators in the hole should wear work gloves on their hands and insulating rubber shoes on their feet.
5. Measures to prevent hole wall collapse
On the basis of familiarity with the geological conditions, in principle, concrete retaining walls or steel casing retaining walls should be installed when excavating pile holes, especially when the diameter is within Pile holes above 1.1m. Each section of the concrete protective wall is 1m high and about 0.1m thick. Appropriate amount of steel bars can be added, and the concrete strength grade is not lower than C10. Generally, 1m deep is dug every day and the formwork is immediately poured to pour quick-hardening concrete, and construction continues the next day.
The bottom expansion of the pile hole should be done as follows: (1) When the bottom expansion of the hole may cause the hole wall to become unstable, corresponding measures must be taken, and construction can only be carried out after approval and signature by the technical person in charge of the enterprise; ( 1) For pile holes that have been enlarged, the pile body should be poured with concrete or the bottom should be sealed in time. For piles that cannot be poured with concrete as soon as possible, the base should not be expanded temporarily to prevent the enlarged head from collapsing.
In the manual excavation process of piles, the method of interval digging should be used to reduce water penetration and prevent soil slippage, so as to prevent the concrete from adjacent piles from being excavated or flushed to form holes. Channeling occurs before initial setting. The hole for a single pile should be dug first in the middle and then at the periphery, and the cross-section should be controlled according to the designed pile diameter plus 1 times the thickness of the retaining wall.
It is generally not advisable to fire blasts in the hole to prevent accidents caused by earthquake collapse of soil or cracking of the retaining wall. If blasting is required based on geological conditions, relevant blasting regulations must be strictly followed.
6. Measures to prevent water inflow from the hole wall
When adjacent piles within 10 meters apart are pouring concrete or the pile hole is filled with water, the dangerous impact on the pile being dug should be considered. Generally, construction should be suspended and no one is allowed to drill holes. Strengthen the observation of water inflow from soil walls at any time, and take timely measures to deal with abnormal situations. When using a submersible pump to pump water, workers can basically drain the water in the hole before they can go down to the hole to dig. When groundwater is abundant, the pile holes in the middle can be excavated in advance to collect nearby groundwater, and use 1 to 1 submersible pumps to pump out the water to dewater deep wells. An emergency soft ladder must be installed in the hole. Electric hoists and cages used by people to go up and down the hole should be safe and reliable and equipped with anti-fall devices. Hemp ropes and nylon ropes must not be used for hanging or stepping up and down the convex steps on the well wall. The upper and lower holes must have reliable communication equipment and clear communication signals.
The workers working in the hole should be rotated frequently, and the continuous working time should not exceed 1 hour to prevent safety accidents caused by fatigue.
7. Other safety measures
If cultural relics, ancient fossils, explosives, cables, etc. are found during construction, the construction should be suspended, the site should be protected, and the relevant departments should be reported in a timely manner and handled according to regulations. , construction can continue.
Before the construction of manually dug piles, a feasible, safe and reasonable construction plan should be prepared based on the on-site engineering geology, hydrological conditions and design requirements, and necessary machinery and electrical equipment should be equipped to ensure that various safety measures are timely in place.
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