Large dams are dams that will cause great damage when the accident occurs, so the survey, design, construction should be very careful. In addition to adhering to the current rules, the author warns that the seven additional issues detailed in the article should be addressed.
Abstract: Generally, high dam is that when happen a catastrophe with it will cause serious damage, so, it must be very carefully while conducting geotechnical investigation, design and construction in order minimize risk. Up to now inVietnamthere is not state standard for geotechnical investigation for high dam. The author of the paper advised that, beside of following present investigation standard for irrigation construction it must be pay attention on 7 problems. They are: using many different methods for investigation works; investigation depth deeper than the depth where discharge of water in water compress test in bore hole less than 0,01 l/min.m; geotechnical surveying larger then usual; paying attention on reservoir-induced earthquakes; instability of foundation hole's slope causing by decreasing of stress; permeability due to high hydraulic head and deformation of rock, especially cement in fracture due to constant load.
The issue of "big dams" in Vietnam has only been considered recently. The dam was only established in 2004. So far, the definition of "big dam" has not been unified. As a general understanding, large dams must be grade I or grade II dams, ie large in size (dam height and water storage capacity), which, when occurring, cause great damage to human and economic life. However, it has also been argued that dams are not large in scale, but after the dams are national key projects, which, when dams occur, cause great damage to the State, must also be classified as large dams. . As such, understandings may vary in size but are consistent with the extent of damage they cause. Therefore, the problem of geological survey of this project is not only related to the size of the project, but also the common issues to consider when conducting the survey to ensure the increase of safety. All for works.
In the field of irrigation - hydropower, so far as said, even the term is not uniform so there is no standard norms that regulate the geological survey works for construction of large dams. So, obviously, when drafting and conducting geological survey works for construction of large dams we still have to comply with current regulations. "Industry Standard 14 TCN 115-2000 - Composition, internal use and volume of geological survey in the stages of project planning and design of irrigation works, "collected enough data to design engineers calculating subsidence, sliding stability and permeability, however we Please note the following:
1. On the application of survey methods
The methods of geological survey works to collect information on the usual geological conditions of the works include:
- Geological survey works
- Drilling and exploring
- Geophysical survey
- Field experiments (CPT, SPT, piercing, hollow compression, cutting, compression in pits, pouring water, draining water, squeezing water in boring hole, ...)
- experiments in the room.
