〓 Research Area : Design of Environmental Infrastructures

Reliability analysis of geo-structures
The stability of the geo-structures, and the natural slopes need to beanalyzed against the severe natural disasters, namely, the earthquakes
and heavy rains. Based on the analytical results, the appropriate counter measures can be determined. The concept of the reliability -based
design can be conveniently used for the decision making for the optimum alternative of the counter measures. The phenomena of the earthquakes and the rains are probabilistic, and the soil parameters havegreat variability. The reliability-based design can include the uncertainties into the designs. The reliability-based design method is mainly
applied to the earth-fill dams here. In Japan, about 160,000 of earth-filldams exist, and many of them are deteriorated, and the countermeasures are rushed. The reliability based-design method can determine
the priority of the earth-fill dams for the countermeasures.

Breached earth-fill dam byearthquake

3-D model of earth-fill dam site forstability analysis

Subsurface survey inside and under geo-structures〓 Prof.
NISHIMURA Shin-ichi

In-situ investigation of subsurface
layer by CPTu

Visualized strength distribution of subsurface layer-Probability for strength of soil to be low-To evaluate the stability of the geo-structures, the subsurface survey
inside or under the geo-structures are important. The geophysical survey and the sounding tests are convenient. In our research, the electricCone Penetration Test (CPTu) is employed, and spatially long andshort-interval tests are mixed to efficiently evaluate the stability of anembankment. The geostatistical method is used to simulate the N value (strength value) distribution and to predict the weak locations inside
the embankments. The synthesized approach of the CPTu and theSurface Wave Method (SWM), which is one of the geophysical methods, is proposed to compensate for the shortcoming of each approachwith use of the geostatistical approach. Consequently, the insides ofthe embankments can be identified accurately, the high resolution of
the spatial distribution of the strength can be visualized.

〓 Research Area : Design of Environmental Infrastructures

Inverse analysis/data assimilation in civil engineering
Inverse analysis/data assimilation is a methodology to assimilate observation data into numericalsimulation models for realistic predictions and parameter identifications. We have developed inverse analysis methods and demonstrated the effectiveness by applying the methods to numericalexperiments, model tests, and actual construction projects. Figure 1 shows conceptual illustrationof cross-hole tomography which is typical inverse analysis method and is designed to visualize
subsurface in a non-destructive way. Figure 2 shows a comparison between the true image of theground and the reconstructed image by the cross-hole tomography.

True image
Figure 1 Cross-hole tomography

Reconstructed image

Figure 2 Comparison between true image andreconstructed image

Numerical Simulations using particle-based methods〓 Assoc. Prof.
SHUKU Takayuki

We have developed simulation codes of the moving particle semi-implicit (MPS) method to predict large deformation and failure behavior in geomaterials such as clay, sand, gravel and theirmixtures. Figure 3 shows a breach process of an earthen embankment due to overflow simulated by the developed MPS method.

Figure 3 Embankment breach process simulated by MPS method

Graduate School of Environmental and Life Science, Okayama University23