Until now, we have examined the prediction methods of the long term strength of silicate grouted sand. However, these methods are predictions under hydrostatic curing condition. It may not be able to apply the prediction method, when seepage water pressure worked. Then, we carried out the experiments in which the seepage water pressures worked. As a result, the seepage water pressure weakened the strength of grouted sand. Next, We measured the volume change and SiO2 leaching of pure grout for 9000 days. Consequently, these stopped almost in the progress of time.
The authors are analyzed the large-scale structure build on the discontinuous rock foundation by the seismic response analysis with non-linear FEM considering the rock joint system using actual seismic records. The seismic response analysis was performed by a kind of the equivalent continuum finite element method with Multiple Yield Model (MYM) introducing cyclic loading elastic-plastic deformation characteristics of rock joints. The analytical results were compared with the observed the seismic response of The 2011 off the Pacific coast of Tohoku Earthquake (Mw = 9.0) and other. As a result, the adequate modeling such as discontinuities and appropriate setting of mechanical properties of rock and discontinuities gives the good result corresponding with the observations. We confirmed the applicability of MYM to seismic response.
This paper states establishment of the theoretical evaluation of the grouting zone during excavation of deep underground tunnel under high water pressure condition. In this study, relationship between allowable pressure and active pressure in the grouting zone is examined by means of one dimensional theoretical solution of pressure due to seepage forces act on the cross-section of the tunnel. The results indicate that allowable pressure is lower than active pressure under conditions of low cohesion. Furthermore, relation-ship between reduction of hydraulic conductivity and active pressure in the grouting zone is examined and it is confirmed that active pressure increases as hydraulic conductivity decreases by grout injection. Therefore, establishment of the theoretical evaluation of the grouting zone based on the results obtained is very important for grouting design.
In order to utilize reclaimed gypsums derived from waste plasterboards as ground improvement materials, thermal behaviors of the reclaimed gypsums and reagent gypsums are investigated in this paper. Furthermore, simple density measuring method of judging quality of the reclaimed gypsums is examined to determine the gypsum hemihydrate content. As the results, it was found that the dehydrate gypsum is changed into the hemihydrate gypsum under thermal condition of 90°C and the hemihydrate gypsum is changed into anhydrite under that of 120°C with heating of 24 hours. The followings were clarified in this paper. The cement density measuring method was available in order to measure the density of reclaimed gypsums; that density was depended on the drying conditions of the reclaimed gypsums; and the density measuring method was appropriate to estimate the gypsum hemihydrate content on reclaimed gypsums. Furthermore, it was found that the quality control method based on the density was effective by calculating the gypsum hemihydrate content from the density values of reclaimed gypsums.
Thermal response tests (TRTs) have been broadly applied to identify thermal properties of hydrogeo-logical environments. In order to quantitatively evaluate the effects of groundwater flow and level, water content on analyzed results of TRTs, TRT equipments for laboratory experiments were constructed so that groundwater level and velocity of seepage flow can be adjusted. Inverse analyses of experimental results were conducted first for cases under saturated conditions with negligible groundwater flow, and showed reasonable agreement of the identified thermal conductivities with those obtained from in-site TRTs conducted under the same geo-environmental conditions as the laboratory experiments. Laboratory thermal response experiments were further carried out for various conditions of seepage flow, groundwater level, water content, and it turned out that apparent thermal conductivities increase according as seepage flow velocity and/or water saturation increase. Furthermore, laboratory thermal response experiments conducted at a constant groundwater level for investigating to the influence of soil-water hysteresis lead to a conclusion that apparent thermal conductivities of soils under drying condition with higher soil water content are larger than those under wetting condition with lower soil water content.
The purpose of this study is to investigate the seismic deformation behavior of improved ground with drainage when excess pore water pressure becomes larger than the allowable design value. The effect of soil improvement using artificial drain against liquefaction is discussed with centrifuge model tests. When the drain pitch was dense enough against the input acceleration, the excess pore water pressure during the shaking was almost smaller than the design value and it dissipated rapidly after the shaking. On the other hand, when the drain pitch was coarse against the input acceleration, the improved ground liquefied and deformed larger than the case with dense drain pitch. However, it is possible that residual deformation of the improved ground with coarse drain pitch was comparable or smaller than that of unimproved ground, and the residual horizontal displacement of sheet pile in the coarsely improved ground was smaller than that in the unimproved ground.
This study proposes a new laboratory testing method for unsaturated zone air permeability, which is the dominant factor for air flow in unsaturated zones, under the condition of higher degree of saturation. The method applies the instantaneous profile method, which is an unsteady state method for measuring an unsaturated hydraulic conductivity in laboratory. To measure accurately fluctuations of unsaturated pore air pressure with extremely high water content, pore water pressure should be separated. Two new types of filters, PTFE filter and water repellent coating filter, are evaluated as an alternative to traditional glass filters, which cannot separate these pressures. As a result, the gas phase pressure detected with these new filters is sharply separated from the liquid phase pressure in unsaturated soil. Theoretically, this new testing method with the instantaneous profile method can measure both water permeability and air permeability for evaluating two-phase flow simultaneously.
Two phase flow problems in soil and rock are very important for underground structures, groundwater environment, and safety assessments of nuclear waste repository. Because of their strong non-linearity, two-phase flow problems are usually solved with numerical simulation. In our study, Mixed Hybrid Finite Element Method (MHFEM) which is considered one of the most robust methods is applied to two phase flow problems. This paper shows general information and validation analyses of space discretization with MHFEM for two phase flow. It is shown that the number and shapes of elements give very small influence on accuracy of the results of simulations. Furthermore, too small number of elements tends to cause numerical oscillation, and it is confirmed that large Peclet number gives problems of numerical stability when pressure formulation is applied for two-phase flow.
The pile method with soil cement around the precast pile body is susceptible to the changes of its pile foundation property followed by the damages to soil cement caused by severe earthquakes. However there has been neither a clear report nor an experimental study of pile foundation with soil cement followed by severe earthquakes. So, this study is to clarify the bearing capacity characteristic to actual piles constructed by pre-boring pile installation method on original ground by checking the condition of soil cement after loading together with off and on vertical loading test and lateral loading test for assumed large deformation caused by severe earthquakes and aftershocks. Here is a review on the bearing capacity characteristic of piles after large deformation with a clarification for the relation between vertical bearing capacity and lateral bearing capacity and condition of soil cement of piles.
High embankment in Shin-Tomei-expressway was built in the Asitaka Loam. This embankment has height of 55 meters. In this site, the significant settlement was concerned over the long term after finishing construction the embankment. This paper shows the data about the settlement obtained by long term observation and laboratory tests. Based on those data, we tried that we evaluated the settlement of construction and future of the high embankment using Ashitaka loam. As a result, it was found that the settlement of embankment under construction produced around 5-9%, the laboratory test had a small settlements for that we calculated from an actual value, the observation during construction at the short span became large settlements, and the residual settlement of around 100cm may occur ten years after the number.
In recent years, a number of embankments affected by rainfall or seepage water collapsed in mountainous regions during earthquake. In this paper, the series of shaking table tests of the embankment affected by seepage water were performed with intention of evaluating the adverse effect of the seepage on seismic resistance. In the shaking table tests, the embankment reinforced by soil nails was also tested aimed to reduce the deformation and the increase of the excess pore water pressure. Furthermore, the calculation method for residual displacement during earthquake was newly proposed, taking into consideration the effect of seepage water and based on Newmark method.
This study focuses on the lateral resistance of caisson type pile of power transmission towers on steep slope subjected to lateral loading. Two medium-scale lateral loading tests were conducted in medium-hard discontinuous rock slopes of 30 and 50 degrees respectively. In order to estimate mechanical properties of discontinuous rock mass, scale effect and variability of shear strength and Young's modulus were evaluated by a series of triaxial compression tests using specimens of diameters from 5 to 30 cm. Nonlinear elasto-plastic FE analysis was used and the computed results were compared with the experimental results. The results shows that (1) the lateral bearing capacity is depend on resistance of front block and pile side, (2) the width of the passive sliding block is equal to three times diameter against the pile width, and the angle of the sliding block surface can be described by Coulomb's earth pressure theory.