I. Overview of pump house foundation engineering construction in water conservancy project construction
As the main body of pumping station construction, the construction procedures of foundation and foundation engineering are usually carried out according to the following procedures: firstly, roads and sites are built and leveled; The second is to establish the construction plane and elevation control network to carry out survey and lofting work; The third is to lay facilities for drainage and lowering the groundwater level; Fourthly, excavating a foundation pit, and stacking and utilizing excavated earthwork according to design requirements; Fifth, if you encounter soft soil, collapsible loess and expansive soil that need necessary treatment, you should deal with them in strict accordance with the design requirements. In the process of pump house foundation engineering construction, there are many factors that will affect the quality, such as climate, materials, personnel, equipment, technology, environment, etc. These factors should be considered and reflected in the construction plan. Thus, whether the construction scheme is reasonable or not directly affects the construction quality of the whole pump house and even the whole project.
Second, concrete measures to improve the construction scheme of pump house foundation project in water conservancy project construction.
(A) the coordination of foundation engineering construction and foundation construction
1. Construction Procedure In the actual construction of the foundation project of the pump house of the water conservancy project, considering the actual operation needs, it is often necessary to coordinate the construction procedure between the foundation and the foundation project according to the construction specifications. The specific construction procedures are described above. First, build roads, level the construction site, then set up the construction plane, and at the same time carry out the work of elevation control network and lofting survey. On this basis, reduce the groundwater level and drainage facilities, foundation pit excavation, special foundation treatment, etc. 2. The premise of pumping station construction of drainage system is to have dry land construction conditions, so as to ensure good drainage in the construction process, improve the bearing capacity of foundation, effectively protect the foundation, and make the rock foundation and building foundation have a better combination while reducing the excavation amount. Once the construction drainage problem is not handled properly, it will not only increase the construction difficulty, but also adversely affect the construction quality, leaving hidden dangers for the operation and management of the project. Construction drainage is closely related to basic geology and excavation procedure, depth, external water level height, underground water level height and construction season [1]. During the construction of pump station foundation project, when planning and setting up drainage system in the construction area of pump station, we should comprehensively consider the topographic and geological conditions, hydrology, meteorology, displacement and other factors of the construction site, and pay attention to the coordination and adaptability with the off-site drainage system. Interception ditches should be set around the foundation pit; The main problem to be considered in the construction of pumping station on canal system is groundwater drainage. There are two main types of foundation pit drainage, one is initial drainage, and the other is regular drainage. At the initial stage of drainage, the composition of displacement includes the accumulated water and possible precipitation in the foundation pit or cofferdam, and the seepage of cofferdam and groundwater during pumping, which needs to be determined through certain calculation [2]. In the routine drainage work, the seepage flow, construction wastewater and precipitation during drainage should be calculated separately, and the precipitation cannot be superimposed with the construction wastewater; The selection of equipment needs to determine the maximum pumping intensity, which should be determined according to the sum of construction wastewater and precipitation and seepage flow. In addition, different drainage methods should be selected according to the actual engineering geological conditions and hydrogeological conditions, such as sump and well point method, in which sump drainage and dewatering method is suitable for unconfined aquifers and well point drainage and dewatering method is suitable for aquifers such as sand, sandy soil and sandy pebbles.
(B) the coordination of foundation pit excavation and related issues
1. When excavating a foundation pit, the excavation section must meet the design requirements, construction requirements and foundation pit slope stability requirements. On this basis, a protective layer with a thickness of 0. 1m-0.3m should be left at the bottom of the foundation pit according to the actual soil and climate conditions and construction conditions, and it should be blocked before foundation construction and dug out in turn. At the same time, the bottom of the foundation can't be over-excavated or under-excavated, and concrete can be used to fill it when it is over-excavated in some places; Abnormal phenomena or unexpected situations in the process of foundation pit excavation should be handled in time. In addition, when the temperature is lower than 0℃, the necessary anti-freezing treatment should be carried out immediately after the foundation protective layer is dug [3]. 2. Foundation Treatment In order to meet the requirements of the project in terms of strength, impermeability, overall performance and durability, the foundation should be treated to improve the foundation performance, and different treatment methods should be adopted according to the actual situation of the project. Commonly used soft soil foundation treatment methods include soil replacement compaction method, sand drain preloading method, vibration water flushing method, high pressure jet grouting method, concrete pouring pile method and dynamic compaction method. If the soft layer of the foundation is not very thick, it can be completely removed and then backfilled with clay, sand and sandy loam. It can also be compacted by crawler crane with buffer device, automatic decoupler and rammer. In addition, when the rock foundation does not meet the engineering requirements, the appropriate treatment methods are backfilling concrete and grouting.
(3) Construction quality control
First of all, do a good job in geological survey and design. At the initial stage of the project, we must do a good job in geological exploration, estimate the bearing strength of geological layer per unit area, and then calculate the total tonnage of the whole water conservancy project, which provides a powerful reference for the construction of pump house foundation engineering [4]. At the same time, the design of pump house is also the main factor affecting the quality and cost, construction period and benefit of foundation engineering. Attention should be paid to the training and screening of designers, and comprehensive design should be carried out from the aspects of material utilization, building structure diagram, energy structure and energy saving, so as to maximize economic benefits on the basis of ensuring building quality. Secondly, the leadership responsibility system is implemented on the construction site. Specifically, it is to implement the quality responsibility to specific personnel step by step, and at the same time strengthen supervision and inspection. It should be pointed out that the multi-person management system is prone to shirking responsibility and chaotic management, which is not conducive to team building and construction site management. Therefore, in the construction of the pump house foundation project, we should adopt the responsibility-to-people construction management system, appoint a special and unique person in charge in the leadership mode for unified management, unified planning and implementation, so as to promote the team building of the construction team, enhance the professionalism and sense of responsibility of the construction personnel, and provide basic management guarantee for the implementation of the construction quality management system. Finally, implement the responsibility system for construction quality. Only implementing the leadership responsibility system can not effectively ensure the smooth development of construction quality management of pump house foundation engineering. Therefore, in order to further reduce the difficulty of management and ensure that the project can be completed on time with good quality and quantity, we should also pay attention to the role of individuals. Therefore, on the basis of recognizing the individual's role in the post, it is necessary to further clarify the individual's responsibilities, rights and tasks in the construction, continuously strengthen the individual's sense of belonging to the enterprise, participation and responsibility in the project construction, and create a construction quality management mechanism with everyone's participation, responsibility, supervision and contribution through the responsibility system. At the same time, the quality problems before, during and after work are trained, strictly investigated and audited to ensure that all links can be effectively connected and achieve layer-by-layer management and assessment.
Three. Concluding remarks
Pump house construction is the main part of pump house construction, which is the key link to realize water resources dispatching and management in the whole water conservancy project construction. Therefore, in the construction of water conservancy projects, we should pay more attention to the construction of pump house foundation project, especially the formulation and improvement of construction scheme, and coordinate the relationship between all aspects and links on the basis of comprehensive consideration of quality, efficiency and benefit.
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