Supervision Outline of a Hydropower Station Project in Hunan
0.1 Project characteristics and key points analysis The fifth power station in Hunan Province in the cascade development scheme of the main stream of Yuanshui River of the * * * hydropower station project is connected with the tail water of Qingshuitang power station at the bottom and the tail water of Anjiang power station at the top. It is a hydropower project focusing on power generation and giving consideration to comprehensive utilization such as shipping. The installed capacity of the power station is 180MW, and the channel is of Class V, which is a large (2) reservoir and a Class II project. The permanent hydraulic structures such as the retaining dam, the power plant and the ship lock are of Class 3. The main quantities of the hydroproject are: 237900 m3 of earth excavation, 2748100 m3 of rock excavation (including 9200 m3 of tunnel excavation), 12200 m3 of earth rock filling, 491200 m3 of concrete and reinforced concrete, 155255t of reinforcement, 5977m of curtain grouting, 3846.4m of consolidation grouting, and 5347t of metal structure installation. The total construction period is 48 months, the power generation period of the first unit is 36 months, the construction preparation period is 7 months, the main project construction period is 29 months, and the project completion period is 6 months. The daily average peak strength of earth rock excavation of the project is 11488m3/d, and the daily average peak strength of concrete pouring is 1428m3/d. The scope of supervision work covers the process and all-round supervision of the civil engineering and metal structure construction stage of * * * Hydropower Station. It refers to the supervision of the whole process from the design stage of the project, through the project construction preparation stage, construction stage to the final acceptance date at the end of the defect liability period stage. After carefully analyzing the bidding documents, we put forward the following control points based on our own experience: (1) The feasibility study report (preliminary design) determines the project scale, standards, structural types and other major issues in the design phase. Based on our company's years of experience in the design and supervision of low head hydropower stations, we will carry out key research on the overall site construction planning, construction diversion, underwater concrete cofferdam construction and concrete cofferdam removal, structural type of energy dissipators, powerhouse layout, foundation treatment design, etc. (2) According to the flood characteristics of the Yuanshui River basin, the success of the cofferdam project will determine the success of the entire hub; We will strictly control the cofferdam construction as the key point of the whole project quality and progress control. The first stage cofferdam of the project has a large amount of work, and the cofferdam closure flow is large. The closure material source must be guaranteed, and the cofferdam heightening and thickening work is heavy; At the same time, the longitudinal cofferdam of the powerhouse is formed in the foundation pit of Phase I, and there are problems of lateral water retaining and stability after foundation excavation during Phase II construction, which must be paid special attention to. During Phase I construction, strict design and construction assurance measures must be taken to effectively strengthen flood forecasting and flood prevention measures. Considering the difficulty of the later removal of the longitudinal concrete cofferdam, we will take corresponding design and construction control measures in advance to ensure that the cofferdam is completely removed without affecting the safety of the project operation. (3) The total construction period of the project is 48 months, and the first unit is put into operation for 36 months, which is 24 months from the start of concrete pouring. The plan is within the normal construction intensity range, but the temporary construction must be completed as soon as possible, especially the construction traffic roads and auxiliary facilities on the site; The construction intensity in the first dry season is too high. To complete the first stage overflow cofferdam, the powerhouse year-round cofferdam, the excavation of the upstream approach channel, the pre excavation above the normal water level of the ship lock, the foundation excavation and foundation treatment of the first stage flood gate, and some concrete pouring tasks, a reasonable construction organization plan must be adopted, especially the configuration of construction machinery and equipment must be compatible with the construction intensity. (4) At the bidding stage, we will assist the owner to reasonably divide the bid sections, prepare rigorous bidding documents, prepare reasonable control construction schedule and equipment supply plan, so as to fully meet the project needs and minimize the owner's risks. In the construction supervision stage, we will carefully study the reliability of the concrete production system and the reasonable warehousing means and process flow, and urge the contractor to ensure the construction intensity of the project. (5) The powerhouse of Riverbed Power Station has complex structural shape, many orifices and intersections, complex flow channel formwork and reinforcement shape, and heavy workload, which requires continuous construction. This puts forward very strict requirements for the reasonable layout of equipment, formwork installation, concrete temperature control, warehousing means and quality assurance measures, as well as the construction coordination of intersections of various processes, We will strictly control the powerhouse concrete construction as the key part of the whole project quality and progress control. In the construction supervision stage, we will carefully study the reliability of the concrete production system and the reasonable warehousing means and process flow, and urge the contractor to ensure the construction intensity of the project. (6) Tubular units have relatively high installation accuracy requirements and are difficult to install. We will strictly control the uniform rise, layering height and rising speed of concrete on both sides of the tubular seat and draft tube steel lining, strengthen the monitoring of the construction process, and strictly control the pouring shape accuracy to meet the needs of unit installation. (7) In view of the different climate characteristics in winter and summer, we will strictly urge the contractor to take effective thermal insulation measures and heat dissipation measures to control the internal and external temperature difference of concrete and ensure the construction quality of concrete works. (8) The delivery, acceptance and installation of a large number of metal structure embedded parts, gates and hoists in this project are the key monitoring parts of this project. The installation of metal structures has large quantities, tight construction period, high construction difficulty, and cross interference with civil construction, so effective monitoring and coordination must be implemented. According to the general schedule of the project, the river was lowered in September 2005 and the second phase closure was carried out in September 2006. Due to the flood in the flood season and the overflow of the foundation pit, the installation period of some radial gate metal structures in the gate dam of the first phase project must be paid enough attention. (9) The basic principle that we must adhere to in the supervision of the project is to carefully review the construction organization design and quality assurance system of the contractor at all stages and divisional works, and to comprehensively balance and coordinate the relevant processes and parts, and finally ensure their full and effective implementation. We will strictly review the construction organization design according to various specific conditions encountered in the project, to ensure that the construction machinery, tools, instruments and meters invested by the contractor are sufficient, the technical quality and quantity of the construction personnel meet the construction requirements, the scheme is reasonable and advanced, the progress safety is effectively guaranteed, the process management is strict, and the concealed works, key parts Site supervision of key processes, find problems, respond quickly, study in time, propose countermeasures, and ensure the quality and progress of each process. (10) According to the new national regulations, the * * * project must pass the safety appraisal before impounding. We will give full play to the rich experience accumulated in the water storage safety appraisal of other projects such as the Yellow River Shapotou Water Control Project, and actively assist the owner in various preparations and cooperation for safety appraisal.
