1 Example Overview
This section of the waterway improvement project is located in Kunshan City, Suzhou City, within the city, the river is 10.233km long, the pile number is JK0+000 ~ JK11+633. JK6+200 ancient small bridge near the requisition of land within the red line of a 500KV high-voltage towers can not be demolished, the high-voltage tower foundation for the reinforced concrete foundation, only 5 meters from the shoreline before Along the line is only 5 meters, the site measured high-voltage line arc sag from the construction zone ground 23 meters.
2 determine the construction program
2.1 gravity retaining wall
The program construction section is large, the excavation pit seriously invaded the high-voltage tower foundation. If the berm before moving forward along the line and can not meet the waterway construction standards or involves a lot of demolition and relocation work, the cost of the project has increased greatly.
2.2 steel sheet pile shore protection
The program construction is simple, shorten the construction period, greatly reducing the construction work surface requirements. After designing and calculating 10 meters steel sheet piles, considering the construction of steel sheet piles, there will be large-scale machinery into the field, if the geological situation is not suitable, but also may have to enter the field auger drilling rig to lead the hole, so many large-scale machinery gathered in the high-voltage towers within the scope of the obvious does not comply with the requirements of the construction safety.
2.3 Bored Pile Shore Protection
The program is mature, safe and reliable, and can be constructed in the narrow construction site while avoiding the cross construction of multiple machines. At the same time with the pile top concrete breast wall and pile body reinforced concrete veneer, not only has a good water resistance, but also play a good role in protecting the foundation of the high-pressure tower. Technically reasonable and feasible, safety should also be demonstrated:
(1) site site machinery safety demonstration. Site site into the pile machine for the GPS-18 type, the top of the frame to the ground distance of 8.5 meters, pile machine frame top and the shortest distance from the high-voltage line has 14.5 meters, according to the "Regulations for the Protection of Electric Power Facilities and Implementing Rules," the provisions of the fifth article, the minimum safe distance of the 500 kV high-voltage line is 8.5 meters to meet the need for a safe distance. The parameters of CAT-320D excavator are: arm length is 3.5 meters, rotating radius is 2.75 meters, the height of the excavator's arm from the ground is about 6 m. The vertical height of CPS-18 piling machine is 8.5 m. According to the full arm extension height of the excavator is only 6.0 m, which is impossible to exceed that of the piling machine, the safety distance of the operation of the excavator is much larger than the piling machine, which meets the needs of the construction. For construction safety considerations, the site does not use the concrete pump pumping concrete, concrete mixer trucks through the construction road into the construction area directly filling concrete, do not have the conditions of the pile foundation through the excavator transfer concrete pouring.
(2) steel cage lifting safety demonstration. Shore protection pile foundation design diameter of 1.0 meters, pile length of 9 meters, the total length of single pile steel cage is 10 meters, according to the actual situation and safe operation height, the normal height of steel cage erection is not more than 11.5 meters, the top of the steel cage and the distance between the top of the high-voltage line and the lower end of the cage has a distance of 11.5 meters to meet the need for a safe distance. This project utilizes excavator assisted, drilling rig winch lifting construction. Due to the short pile length of this project, a single section of reinforcing cage can meet the design requirements, without the need to lengthen the reinforcing cage, if the pile length of the project is longer, the welding of reinforcing cage joints should try to increase the number of welders and welders, to shorten the time of installation of reinforcing cage. In the end, we determined to use bored pile shoring for construction.
3 Construction safety control workflow
Survey the scope of high-voltage tower foundation → site cleaning and leveling →measure the distance of high-voltage line from the ground level of the piles →understand the appearance of various machinery at the construction site whether it meets the requirements of the safety distance →make a safe construction program under the high-voltage line →report to the supervisor and the security department of the local grid company for approval →strictly in accordance with the approval of the program of the construction →construction of the pre-construction safety education and safety technical briefing →construction process and safety technology briefing → safety monitoring during the construction process.
4 Construction Safety Management Measures and Precautions
4.1 Construction Safety Management Measures
(1) Carry out the policy of "Safety First, Prevention First, Comprehensive Management", and comply with national and local safety laws and regulations. (2) Set up a safety leading group composed of project manager, technical person in charge, full-time safety officer, etc. The full-time safety officer is responsible for daily safety inspection, often communicates with the safety guardian of the local power grid company in Kunshan to supervise the construction personnel to carry out the production according to the relevant safety regulations, and at the same time, the piling construction team should set up a part-time safety officer. (3) Strictly implement the safety production management system, especially "safety education system, safety inspection system, safety reward and punishment system", etc., the construction personnel on site for high-voltage line safety education and training, so that all the construction personnel on site to master the high-voltage line safety construction operation procedures, the safety officer should be a good construction operator for safety and technical briefing. The safety officer should make a good safety technical briefing to the construction operators. The safety leading group regularly or irregularly inspects the safety of the construction site, and issues a "Notice of Rectification of Hidden Dangerous Safety Problems" and orders rectification within a certain period of time. (3) The project department establishes the production safety responsibility system, and clarifies the safety responsibilities of the management personnel at all levels and the on-site construction personnel. (4) the development of anti-electrocution, fire emergency plan, before entering the construction site, the security leading group is responsible for organizing the relevant emergency plan for safety drills.
4.2 Construction Safety Protection Measures
(1) The risk of the pile driving construction process is the greatest directly under the high voltage line. Therefore, the operation area under the high-voltage line tower is equipped with a safety officer to patrol and monitor the construction site 24 hours a day. (2) In order to ensure the safety of construction, outside the safety distance of the high-voltage line using protective fences and hanging warning signs and other protective measures. Measuring personnel should retest the safety distance to confirm the safety distance is correct. (3) When the pile driving machine is installed on the site, the site should be level and stable, without subsidence and collapse, the pile driving machine should be grounded and protected according to the relevant requirements, and the pile driving machine should be tested comprehensively before the construction under the high-voltage line to ensure that the pile driving machine can work normally within the range of the high-voltage line. (4) When adverse geological conditions are encountered under the high pressure line and normal drilling is not possible, or when the drilling rig needs to be repaired and replaced due to mechanical damage, the unrelated construction personnel shall evacuate from the site and wait for as few as possible on-site maintenance personnel, and at the same time, the site shall be prepared with maintenance spare parts to reduce the maintenance time. (5) Special operators, must be licensed to work, enter the construction site personnel, must wear a helmet, and according to the provisions of the safety protective equipment. (6) steel cage lifting, the scene of non-lifting personnel are withdrawn from the high-voltage line outside the scope of influence, and by the lifting conductor is responsible for directing the lifting, lifting before the wire rope must be checked, there shall be no slip wire broken wire phenomenon, to prevent the wire rope suddenly breaks rebound to the high-voltage line. (7) When drilling construction, the drilling speed shall not be too fast or change speed suddenly, which will cause the pile driver to shake violently; (8) There shall be warning lines and warning signs around the mud pool, and there shall be warning lights at night; (9) Tie up the coverings of the rebar processing area and the rebar cage stacking area tightly, and all the miscellaneous matters and coverings at the site shall be compacted, so as to prevent the windy weather from blowing into the high-voltage line, which will cause the line to be short-circuited and electrocuted; (10) The equipment such as rebar Cutting machine, bending machine and other equipment in accordance with the provisions of the zero, grounding protection; (11) pay attention to the local weather forecast, in the case of thunderstorms and other inclement weather conditions, construction must be stopped, the construction workers evacuated in advance of the high-voltage line range. Before and after rainstorms and high winds to check the site temporary facilities, electrical equipment, temporary power lines found tilted, damaged, leakage, etc., should be reinforced and repaired in a timely manner, to eliminate the risk; (12) high-voltage lines shall not pile up the earth, do not pile up flammable and combustible materials; (13) all personnel are not allowed to climb high-voltage line towers, and it is prohibited to throw objects to the high-voltage line.
5 Conclusion
Waterway improvement project construction scope is wide, more safety hazards, construction personnel, especially full-time safety personnel should often patrol the construction along the line, able to detect safety hazards in a timely manner.
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