In the current construction of water conservancy and hydropower projects, the construction of rockfill dam is the most common construction technology mode and method, and the selection of construction design and construction technology has extremely strict particularity in the construction process. This phenomenon is mainly manifested in the difficulty of blasting control in the process of engineering construction, and the scope of blasting construction technology is getting wider and wider. In blasting engineering, the main difficulties in construction are technical design, selection of blasting equipment, construction organization design and technical safety management. Therefore, we need to carry out systematic and comprehensive control and management in the current engineering construction, and carry out in-depth and systematic thinking and improvement on various problems existing in its construction.
I. Overview of CFRD
Concrete face rockfill dam is widely used in current water conservancy construction, and its construction technology, construction quality and construction benefit have been concerned and recognized by people. At present, in the construction of concrete face rockfill dam, it mainly refers to the dam structure of water conservancy project formed by layered rolling and filling of rockfill or gravel. This kind of dam structure adopts concrete face slab as the main seepage control dam in the construction process, which is called concrete face rockfill dam or concrete face slab dam for short. This dam structure first appeared at the beginning of last century. At that time, the concrete face rockfill dam was mainly a construction stage of rockfill dam, and it was constantly improved and perfected with the development of social science and technology.
1, application and characteristics of materials
1. 1. In the material research and analysis of concrete face rockfill dam, mainly by studying the engineering characteristics of soft and hard rock materials, aiming at how to reasonably apply excavated materials in construction, cushion materials and group materials are determined through self-healing research. At the same time, the reasonable deformation characteristics of rockfill are studied and analyzed repeatedly through the field construction blasting test and field rolling test.
1.2. In the application analysis of stress and deformation of rockfill, the rheological characteristics of rockfill are comprehensively analyzed and studied, and good progress has been made in determining hexagonal model and parameters. Through the study of face slab and neutralization analysis of rheological factors of rockfill, it provides a basis for comprehensive construction and design of dam.
1.3. In the aspect of crack durability of face slab, the crack resistance of concrete and its influencing factors are studied, the crack resistance of face slab is analyzed, the reasonable reinforcement ratio and reinforcement position of face slab are studied, and the crack resistance measures of face slab are put forward accordingly; Study the corrosion mechanism of concrete, and reasonably predict and evaluate the corrosion durability of concrete.
1.4. In the construction of peripheral joint water-stop structure, the conventional water-stop structure is reasonably demonstrated, a safer new structure is put forward, and the self-healing structure is studied. In the construction and analysis of water-stop materials, the performance of domestic plastic caulking water-stop materials has surpassed that of foreign related research materials, and a major breakthrough has been made in the water-stop and analysis design of bottom copper. These research results and achievements can basically meet the needs and construction of 200m advanced panels in application.
In the application field and distribution of hydraulic engineering construction, the dynamic force of concrete face dam is obtained through two-dimensional and three-dimensional vibration model tests, and the automatic vibration frequency and dynamic characteristics corresponding to various test cracks are obtained. In order to provide comprehensive data for checking and improving the calculation method and program, the application measures and programs of three-dimensional effective stress and linear dynamic of panel are studied. Reflection and analysis of measures and methods for roller compaction of rockfill dams with little or no water.
2. Blasting parameters
In the narrow construction area of water conservancy and hydropower concrete face rockfill dam, the excavation of rock layer is subject to many restrictions, and the seismic capacity between rock layer and shaft wall is weak, so certain methods and means must be taken to limit and control it in the construction process. Generally, in construction, small-caliber guns and segmented micro-blasting are usually used for construction. However, the selection of blasting parameters for pile diameter excavation can not be directly applied to the blasting excavation parameters of small mines, nor can it be controlled by fixed parameters. The control of parameter value should be based on the excavation diameter of pile well, and other factors such as weathering degree and cracking condition can not be ignored, so as to ensure that the explosives used can meet the influence of various factors.
Second, the engineering construction case analysis
1, project overview
A hydropower station is located on Baishui River in Baishui Forest Farm, Qiashui Town, Huaiji County, northwest Guangdong Province. The rainwater collection area above the dam site of the power station is 170 km2, with an average annual flow of 6.5 1 m3 per second and a total installed capacity of 36,000 kilowatts. The power station is a diversion power station, which is a water conservancy hub integrating power generation, flood control and irrigation. The whole hub consists of water storage dam, spillway, diversion tunnel, power station and 1 10KV booster station, in which the dam is a reinforced concrete face rockfill dam with the maximum height of 1 10.7m and the crest length of 288.3m.
2 The location and geological conditions of the stockyard
There is a material yard on the left bank of the valley downstream of the dam site, which is a typical valley landform with a linear distance of nearly one kilometer to the dam site. The ground cover of the material yard is 1 ~ 2m, and some rocks are exposed. The material yard is distributed along the river valley, with a utilization length of 300m, an elevation of 5 10/0m ~ 340m ~ 340m, and a reserve of more than 2 million cubic meters. The rocks in the quarry are mainly Yanshanian gray-white fine-grained granite and gray-white and flesh-red medium-grained granite with single lithology and simple geological structure. There are two faults, F 102 and F 165, which are small in scale and well filled, and have little influence on dam material mining and blasting, dam material quality and dam slope stability. The four groups of main joints in rock distribution form natural cutting with each other, which is beneficial to blasting crushing. The physical and mechanical properties of rocks are tested in the laboratory by sampling from excavated sections and open holes. The results show that the specific gravity of the rock is 2.64 ~ 2.65, the density is 2.5 1 ~ 2.64g/cm3, the porosity is 3.03 ~ 4.92%, and the saturated water absorption is 0.2 ~ 1.0 1%. The compressive strength of fresh rock is between123.2 ~178.1MPa, and the average f value of proctor hardness coefficient of rock is about 15, so it is hard and not easy to explode.
3. Advantages of blasting construction
3. 1 From the results of blasting test, rolling test and a large number of excavation sampling tests of dam filling, it can be known that all three kinds of dam-building stones show continuous particle gradation and uneven coefficient Cu >；; 10 (transition material of copper >; 15), fine particles smaller than 5mm account for about 10%, which is beneficial to vibration rolling. It can be seen that the drilling and blasting parameters selected for blasting are reasonable and feasible, which can be used as a reference for related projects.
3.2 The use of 250mm large-diameter drilling for deep-hole bench blasting mining dam materials is prone to more over-diameter stones, and the linear charge should be strictly controlled between 30 ~ 40kg/m, so as to shorten the length of the blocked section as much as possible. The screened stones in the material yard should be decomposed for the second time, and unqualified dam materials should not be filled on the dam.
3.3 When blasting dam materials, in order to increase the content of medium and coarse particles in the secondary batching, consider appropriately increasing the drilling spacing, and the selected chassis resistance line value should not change greatly. In the observation of the blasting effect of mass production of dam materials in the future, there are more over-diameter and large-diameter particles than the general deep-hole bench blasting with a hole diameter of Ф100 mm. In production practice, better results can be achieved by controlling the linear charge density and reducing the length of unnecessary blocking section. In the process of dam filling, a large number of excavation and sampling tests further confirmed that the 250mm large-diameter drilling and mining dam material was successful in a hydropower station dam project, and the technical indexes such as particle gradation, dry bulk density and porosity after rolling all met the design requirements.
Three. Concluding remarks
In the current social development, water conservancy project construction has become an indispensable and neglected important part of architectural engineering design. In the design process, the comprehensive analysis of the performance of various foundation materials of rockfill dam is reasonably used to ensure the rationality and uniqueness of the design, and also to ensure detailed disclosure to all builders in the construction process to improve the engineering quality.
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