Kohkichi Kikuchi

In situ experimental studies on improvement of rock masses by grouting treatment

Abstract One of the purposes of consolidation grouting for dam foundation is to improve mechanical properties of rock masses. In this paper, we would like to discuss in situ experiment carried out in order to explore the grouting effects of rock masses on mechanical properties. This experiment is mainly consisted of operating, electromagnetic and elastic wave prediction and borehole expansion test. The results obtained through this study are listed as follows. o 1. The change of permeability zone can be identified by change of electromagnetic wave amplitude. 2. Further injection steps may help rock masses to become uniform in terms of electric characteristics. 3. The change of elastic wave velocity by grouting injection also explains uniformity of rock masses. 4. Grouting injection can improve deformability of rock masses. 5. For more deformable rock masses before grouting injection, the more mechanical improvement will be expected. 6. The rheological model explaining grouting injection effects can be verified. This model shows a tendency that poor rock masses which have lower mechanical properties, can be well expressed the experiment results.

Stochastic block theory for initial support decision of large slope

Abstract Stochastic Block Theory is suggested as the management tool for the decision for initial support of key block before every discontinuity trace of the block has not appeared on slope surface, in other word, in the moment some of the discontinuity traces of the block have appeared. The probability of forming a removable block by the next excavation can be calculated by taking rock joint distribution into account. The applicability of the theory is examined using the joint trace maps.

Study on Improvement of Dam Foundation by Grouting Treatment.

The purpose of consolidation grouting for dam foundation is to improve the permeability and mechanical properties of rock masses. For permeability, the grouting effect is usually confirmed by the permeability test at check holes. But for the change of mechanical properties, it has been difficult of confirmation. So, the mechanical improvement of foundation by grouting, like the changes of elasticity and strength, has not been considered in dam foundation design. In this study, an in situ experiment has been made in order to examine the grouting effect on mechanical properties of rock masses. The testing yard where the experiment was performed was 10m square, and 13 boreholes for grouting, divided into four (4) stages, were laid out. These boreholes had the length of 7m each, and the injection material was cement mixed with water. The experiments mainly consisted of elastic wave prediction and borehole expansion tests. As the results, the followings were obtained.(1) The change of distribution of elastic wave velocity by grouting represents the uniformity of rock masses.(2) Grouting can improve the deformability of rock masses.(3) For more deformable rock masses before grouting, the more mechanical improvement is achieved.(4) The reological model can be used to explain the grouting effect. By this model, the experiment results of poor rock. masses, which have lower mechanical properties, can be well expressed.

Prediction Equations for Weathering of Cretaceous Kitakyusyu Granite by Outdoor Exposure Test.

In order to predict the weathering process of rock foundation and rock materials for engineering purpose, fundamental studies have been carrying out to investigate the factor of weathering, changes of some properties and rock deterioration mechanism by weathering.The outdoor exposure tests on Cretaceous Granitic Rock (Kitakyusyu granite) were carried out in this study. The columnar specimens used in this experiment are composed of a series of rocks that include fresh rocks to weathered rocks. Their weathering properties were clarifed by the outdoor exposure, and the regression equations for the deterioration process were obtained as a function of outdoor exposure time. Using these equations, one can predict the weathering process from the initial physical and mechanical indices of rocks.

Stochastic Block Theory for the Observational Construction of Large Rock Slope.

For the excavation and the supporting of large rock slope, the observational construction method is becoming increasingly important in order to carry out the support decision immediately, by taking discontinuity distribution into account, because of the difficulty of supporting after some benches have already cut.It is well known that slope stability is strongly controlled by discontinuity distribution in the case of the hard rock masses. Goodman and Shi (1982) proposed “Block Theory” for the estimation of slope stability considering discontinuity distribution. Key block, however, can be found out after all the discontinuity traces of the block appeare on the slope surface. In that moment, the key block is unstable and can move out of the slope.Considering the above, the authors developed “Stochastic Block Theory” for the prediction of the key block before all the discontinuity traces of the block have not appeared on the slope, in other word, in the moment some of the discontinuity traces of the key block have appeared.Using Stochastic Block Theory, the probability of becoming a key block can be estimated concerning the block surrounding some discontinuity traces and bench.