PS (Paper Sludge) ashes are discharged from paper mills. In this study, to efficiently utilize them for the treatment of sludge or construction waste soil, a simple testing method is developed to measure the water absorption performance of PS ash. From the test, the performance index named as water absorption ratio wab can be obtained. By using the index, water absorption characteristics of various PS ashes produced with different incineration methods can be evaluated. Furthermore, in order to obtain more stable and higher water absorption performance from the various PS ashes, several treatment methods considering the incineration conditions were also developed. Then a mixture design method which consider the consistency characteristics of mud and water absorption performance of PS ash simultaneously, is proposed for the mud modification. Finally, the effects of particle crushing of PS ashes on the water absorption performance are investigated.
The two major subjects were considered based on a result of the shaking experiment of a slope model under 1G field in this paper. One is the behavior to being unstable from stability of a slope. Second is applicability of Newmark method for the behavior beyond the stable limit behavior. The existing experimental data obtained by shaking table tests of slope models under 1G were used. The slope models consisted of 3 layers such as surface layer, weak layer and base layer. Among the models, the heights were 1.0m for small size model, 2.0m for medium size model. The occurrence location of slip surface is restricted in the weak layer. It is found that slip surface is formed by connecting shear cracks which have formed discretely after generating a tensile crack in the top, and that the yield acceleration is the same with the acceleration which acts on a slope when collapsing against a sinusoidal input wave. Furthermore, for the experiment that three conditions including the acceleration at the time of the slip surface formation are clear in the conditions that are necessary for the application for Newmark method, it is found that the results that the estimated value is less than the experimental value have the same tendency with the existing studies and that it was the point to take into account when designing.
In the pre-ground improvement method, the ground around the tunnel is applied by the replacement method or the improvement method. In previous researches, the optimum ground improvement area was discussed through the numerical simulations at the excavation process. However, the seismic behavior of the tunnel was not clearly discussed. In this study, dynamic centrifugal model experiments under a gravitational acceleration of 50 G were conducted to clarify the dynamic behavior of the shallow tunnel with pre-ground improvement. In addition to the simple tunnel without ground improvement, two ground improvement patterns; (1) the ground around all the cross-sections of the tunnel was improved, and (2) the ground around the crown of the tunnel and the top section was improved, were investigated. From the results, it is confirmed that when the entire ground around the tunnel was improved, shear deformation of the tunnel could be suppressed by the increment of the whole rigidity of surrounding ground. On the other hand, when the ground around the tunnel crown and the top section was improved, the response of the tunnel was amplified by the concentration of the weight at the upper part of the tunnel. Moreover, large cross-sectional forces were generated at the boundary between the improved and unimproved ground.
The authors have performed many investigations on the stability of cliffs with toe erosion in Ryukyu Archipelago. It is found that the degradation of a lot of erosion cliff failure surfaces was almost uniform. For example, a failed cliff with erosion on Sesoko Island was characterized as a three layered structure with different degradation degrees. Therefore, it is necessary to research the causes related to crack propagation and rock masses deterioration using different technique. In this study, we utilized an infrared camera, model experiments using shaking table and a series of finite element analysis. The finite element analyses were carried out by considering a three layered structure with different deterioration states. The site investigations, model tests and numerical analyses revealed that the conditions of degradation should have been different as the time of occurrence of tensile cracks was different in each layer. It has found that the tensile strength of rock mass should range between 0.24 and 0.35 MPa from the collapsed histories.
As a cause of the seismic damage to embankments, liquefaction of the sandy ground located under an embankment has been mainly focused in the past. However, many embankment damages were observed also in river levees constructed on non-liquefiable ground, in which thick clay and/or peat layers were deposited, during the 2011 off the Pacific coast of Tohoku Earthquake. In this research, to investigate the dynamic deformation mechanism of an embankment constructed on a clay deposit which received a consolidation history, a series of shaking table tests in a centrifugal field were carried out by changing the consolidation state (i.e., normal consolidation or overconsolidation) of the clay deposit under an embankment, the embankment material, and the input level of an earthquake motion. The experiments have revealed that an embankment constructed on a normally-consolidated clay deposit and affected by the consolidation settlement showed a larger seismic damage compared to that on an overconsolidated clay deposit, although the embankment settlement due to the earthquake loading was smaller than that arising from the consolidation settlement of the normally-consolidated clay. This suggests that the stress state within the embankment changed from its initial state immediately after the construction of the embankment due to the consolidation settlement of the clay deposit. To estimate the seismic damage of an embankment constructed on a clay deposit, it is thought that the influence evaluation of the consolidation history in the clay deposit becomes important.
Nowadays, the cut and embankment slopes of expressway are damaged due to heavy rainfall and large earthquakes. On the other hand, the expressway facilities are worried about the age deterioration since about 40% expressway facilities has been used for more than 30years. Firstly, the authors showed the four cases of major damages in the view point of the inducements and predispositions. In addition to this, the predispositions of the slope damage such as a topography, a geology, and a geomaterial composed which greatly affects the damage were analyzed with using total 213 damage data obtained from the experience for recent 25 years (1994-2017) in Tohoku district. As the results, it was found that vulnerable slopes have a certain characteristics and that the drainage capacity of the cut and embankment slope affects the vulnerability of slopes.