Dynamic injection is a technique which efficiently injects with high dense slurry into rock fractures. This technique improves the fluidity and penetration properties of grout materials, thus preventing blockade phenomena. In this paper, the efficiency of the dynamic grouting and the optimum condition of injection are confirmed from the results of the large-scale injection tests with a fine model fracture and a large fracture, the rheological tests using a viscometer specially designed for its test, and the analysis of unsteady flow through a parallel fine slit. In addition, the paper describes an outline of the dynamic grouting system for on-site works.

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Grouting specifications for dam foundation are often formulated based on a previous experience in projects with similar foundation conditions. Grout injection is normally started from thin mix with water cement ratio of 10 (by weight). Thicker mix as the starter is considered to be unfavorable for successful filling of the joints; namely the inherent higher viscosity may cause the mix to settle at a reduced penetration or plugging near the injection hole. In our laboratory tests on penetration properties in jointed rock, cement grouts of different water cement ratios (W/C=0.8, 1, 2, 10) were injected into plane-parallel joint plane model with aperture from 0.1mm to 1mm. Grout mix with W/C of 2 exhibits penetration properties similar to thinner mix of W/C of 10 with respect to the plugging property, penetrated distance, and critical sedimentation velocity. Cored samples from the grout curtains were analyzed by X-ray diffraction test. The comparison of the calcium-compounds contents with the laboratory mix have revealed that grout curtains injected by thicker mix have been found to be successful. Both the laboratory tests and the field verification have suggested that foundation grout starting with thicker mix of W/C of 2 was found to be more successful than that with thinner mix. It should be noted that injection of thick mix as the starter will lead to economical advantage by a reduction in grout operation time.

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Conventional continuous concrete mixer are considered very speedy in terms of mixing rate, but at the same time, have some problems particularly in the quality control of the concrete in comparison with that from conventional batch type mixers. In recent dam construction projects, the need has been highlighted to introduce an effective continuous construction method for concrete, which will rationalize site work and contribute to energy-saving on sit. Taking into consideration the above-mentioned problems, the main aim or this study was to concentrate on a development of the new continuous concrete production system for such dam construction projects. The proposed new system, which contains energy-saving gravity mixer, has many advantages for mixing efficiency. Various mixing experiments were carried out to evaluate mixing efficiency of this system. In conclusion, it was verified that this plant satisfied the requirement for the technical assessment as recommended by JIS. And it is clear that this mixing plant can produce a similar quality of concrete to that from conventional one.

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Although grouting is one of the most general methods for dam foundation treatment, fundamental parameters for injection such as injection pressure and W-C ratio are empirically decided in general. This paper covers the following studies; 1. Statistical analysis of grouting data obtained in an actual construction work, 2. Suggestion of injection method, 3. Verification of the suggested method (High Thickness-Low Pressure Grouting Method: HTLP Method) by in-situ experiments. As the result of those examinations, it is found that HTLP Method is essential for effective and efficient grouting.

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Centrifuge model tests were carried out to investigate the pore-water pressure response and hydraulic fracturing in embankment dams, caused by a rapid increase in the height of reservoir water during flooding. Embankment behavior at failure during flooding is discussed to consider whether sliding of soil mass, interior erosion (piping) of fill materials or exterior erosion by the action of over-flow water is the most influential factor in the failure process. Transmission of pore water pressure in the fill is associated with its permeability and the rate of reservoir filling, which is another important subject to be discussed how and to what extent it may cause such catastrophic damages. FEM unsteady saturated and unsaturated seepage analysis was conducted on the pore-pressure behavior in embankment dams before flooding to give supplementary discussions on the mechanism of seepage failure during flooding, and also to examine reliability of the test results and validity of applying the centrifuge model test on this subject.

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