Containment technique using cut-off walls is a valid method against contaminants in subsurface soil and/or groundwater. This paper states laboratory testing results on hydraulic barrier performance of Soil-Bentonite (SB), which is made by mixing bentonite with in-situ soil. Since the bentonite swelling is sensitive to chemicals, chemical compatibility is important for the hydraulic barrier performance of SB. Hydraulic conductivity tests using flexible-wall permeameter were conducted on SB specimens with various types and concentrations of chemicals in the pore water and/or in the permeant and with various bentonite powder contents. As a result, hydraulic barrier performance of SB was influenced by the chemical concentration in the pore water of original soil and bentonite powder content. In the case that SB specimens have damage parallel to the permeating direction, no significant leakage in the SB occurs by the self-sealing property of SB. In addition, the hydraulic conductivity values of SB have excellent correlation with their plastic indexes and swelling pr essures, thus these properties of SB have some possibility to be indicators for estimation of the hydraulic barrier performance of SB.
Advantageous aspects of sandwich-type reinforced earth structures combined with geosynthetics and sand mat are highlighted in this paper. Those aspects were elucidated by two kinds of laboratory tests : (1) large consolidation tests for improvement of hydraulic conductivity and (2) model footing tests on improvement of bearing capacity and deformation characteristics for reinforced earth structures, including both vertical permeability and horizontal transmissibility characteristics of geosynthetics results from both laboratory tests indicated the following: i) Hydraulic conductivity of geosynthetics used for this type of earth reinforcement can be maintained for a long period. Such conductivity sometimes disappears, particularly because of clogging when geosynthetics are adopted in embankment construction using fine-grained soils. This fact indicates that the sand mats which are laid above and beneath geosynthetics play a salient role in preventing clogging of geosynthetics that occurs by intrusion of fines from cohesive soils. ii) Sandwich-type reinforcement combined with geosynthetics and sand mats increases stability and decreases deformation of earth structures. In particular, the sandwich structure is effective for providing toughness, which has remained an important issue for reducing infrastructural maintenance and costs. In the later part of the paper, conventionally available stability analysis was carried out to propose the design procedure for reinforced earth structures and at the same time numerical analysis was also conducted to ensure the applicability of the hybrid-sandwiched earth reinforcement newly proposed in the current paper. Finally, based on the horizontal placement by means of HBS described in the current paper, the vertical drain procedure using the sandwich structures for accelerating consolidation and increasing stability of soft soils is also suggested for the future research and investigation.
In this paper, authors proposed the newly calcite precipitation method for peat. This method can be isolated the urease production bacterium. The main outcomes of this research were: (1) Proposed method can be isolated the urease production bacterium from peat. (2) Urease production bacterium from peat can be accelerate the calcite precipitation at the high pH and high chlorine conditions. (3) Calcite precipitation speed was slower than the B. pasteurii . (4) Proposed method can accelerate the soil strength (Over 400kN/m2 -1D compression test) after 2 week cultivation.
A basic framework and a method to evaluate uncertainty involved in spatial variability of geotechnical parameters and resulting statistical estimation error in geotechnical reliability analysis are proposed in this study. The soil prole is model by a stationary random field, which is simplication and idealization of the real ground. The local average at an arbitrary point in the random field is estimated from limited samples obtained from the same filed. The two estimation methods are proposed, namely the general estimation and the local estimation The relative positions of samplings and of the construction are not considered in the former, whereas they are considered in the latter. An example is attached to illustrate the proposed method.
Parameters for the migration of components in the gas system become molecular diffusion and Knudsen diffusion with tortuosity and dipersivity. Hibi et al. developed the method for obtaining these parameters by using column experiments in the previous study. Tank experiments and numerical simulation were conducted in the present study for verifying that values obtained by using the column experiments were adequate. Carbon dioxide was injected in to the tank filled dry Toyoura sand or soil mixed Toyoura sand with bentonite, in where these parameter were obtained, and gas adjusting components of oxygen and nitrogen. The numerical simulation was carried out by using the simulator with Dusty gas model and characteristic finite element scheme and by employing the parameters obtained by the column experiments in the previous study. Therefore it was found in this study that these parameters were adequate.
The paper proposes a simple and yet practical reliability based design (RBD) scheme which takes into account the characteristics of geotechnical design. The proposed scheme evaluates the reliability by basically separating the geotechnical analysis and the uncertainty analysis, and reuniting them by the response surface (RS) and Monte Carlo simulation (MCS). As a result, RBD can be easily done making the best use of geotechnical analysis tool newly developed. The philosophy and procedures of the scheme are presented through a real and complex geotechnical structure design, i.e. seismic design of 12 km long irrigation channel against liquefaction. Through this design example, merits of the geotechnical RBD are shown, such as amount and quality of investigation data on the reliability evaluation, major sources of uncertainties in RBD, and suggestions for priority of countermeasure locations and additional investigations.
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 and laboratory tests were made in order to examine the grouting effect on mechanical properties of rock masses.
In the vacuum consolidation method, the vacuum pressure acts on the direction of the inside of the improvement region. When the embankment is used together, the lateral deformation decrease and the rapid construction of the embankment are possible. However, the FEM analysis is necessary to forecast such an improved effect. In this paper, the improved effect and the deformation characteristic were verified about the vacuum consolidation method executed by the Wakasa construction. Moreover, soil-water coupled FEM analysis was executed, and the use method to the execution management etc. were examined. In the Wakasa construction, it was confirmed that the vacuum consolidation method demonstrated a high effect in the deformation decrease of the surrounding soil, the accelerating consolidation, and the term of works shortening. The executed FEM analysis can reproduce the improved effect of the vacuum consolidation by high accuracy. In the Wakasa construction, a stable construction of embankment has been achieved by using this analytical result for the execution management.
Pull-out test of model piles was conducted by varying the pull-out velocity and skin friction of piles using a seepage force similitude model test apparatus. Due to the seepage consolidation under the pressure of 150kPa, the effective stress distribution in a prototype saturated soil of 17m could be successfully reproduced in the model ground of 28cm thick, in which the pull-out tests were carried out. The pull-out load rose to a peak value at small displacement, and then decreased to a residual value. At the same time, pore pressure in the vicinity of the pile decreased due to suction near the tip and the positive dilatancy near the pile skin. The maximum pull-out load, pile axial load, side friction and the corresponding displacement increased dramatically with increasing pull-out velocity. It was found that these rate-dependent trends become more prominent with increasing skin friction.
The subsidence of the ground during an earthquake is often understood to be a phenomenon induced by the liquefaction. However, the subsidence possibly occurs even in an unsaturated ground without the increase in excess pore water pressure during earthquake. It is thought to be induced by the shake packing of soil particles due to the oscillatory load during the earthquake. In this study, we discuss the relationship among the shake packing behavior, vibrating conditions and soil properties through the model test. In the model test, an electrical method was employed for monitoring the tangency among the particles during oscillation. Coal, which was an electrically conductive material, was employed to simulate the relative movement of soil particles. The electric resistance of coal depends on the tangency among the particles, therefore the tangency among coal particles during oscillation was evaluated by measuring their electric resistance. The results reveal that the relative movement among the particles can not be uniquely determined by the acceleration of the oscillation and that the ratio of particle size to the amplitude of the oscillation can be an important factor governing the relative movement among the particles.
If sandy soil with appropriate gradation is compacted, hard and dense ground will be generated. Even if the soil material is hard enough against shock load, the permeability of the soil decreases significantly. This paper examines the improvement effect of playground surface by waste crushed shell mixing technique. The following conclusions are obtained from the present study: 1. The maximum dry density of the sandy soil increases gradually by mixing the crushed shell. However, if the crushed shell is put into the soil too much, the density decreases conversely. 2. Although the density of the soil sample becomes high by mixing the crushed shell, the coefficient of permeability increases. 3. The soil particles once attached to the shell is not washed away easily. 4. The crushed shell doesn't change the quality of groundwater so much. 5. This repair method is applicable to improvement of playground surface.
Although waste recycling has been promoted in response to increasing environmental awareness in Japan, its marketability is being questioned due to the recycling cost. The ultimate goal of waste recycling is to reduce the environmental load. In this paper, we examined the evaluation method for social environmental efficiency to socially evaluate waste recycling, by incorporating environmental load as an environmental cost in addition to the direct cost. Specifically, by applying sensitivity analysis and Monte-Carlo Simulation, we conducted the social environmental efficiency evaluation including consideration of uncertainties, because waste recycling involves various uncertain elements. As a result, we were able to quantitatively evaluate the social environmental significance of construction sludge recycling while focusing on the particular construction sludge with a lower recycling rate.
On March 11th 2011, the Tohoku-Oki earthquake (Mw9.0) was generated along the Japan Trench and triggered a lot of aftershocks. The extent of damage caused by these earthquakes were enormous. One of the damages caused by this earthquake is land subsidence induced by soil liquefaction. Here, we focus on the soil liquefaction at waterfront area along Tokyo bay. In this study area, it was reported that sand boiling as well as soil liquefaction was widely found especially in the artificially filled ground. However it is difficult to reveal quantitative degree of the surface deformation associated with soil liquefaction only using ground-based observation system. Therefore, the goal of this study is to estimate surface deformation induced by the soil liquefaction in this area using Differential Interferometric SAR(DInSAR) analysis. In the result, we succeeded in estimating distribution of the surface deformation associated with liquefaction at the waterfront area and found that surface deformation is not uniformly occurred in the artificially filled ground.
A series of bender element tests was performed on sand and natural clay mixtures with various water contents and fines contents. The boundary between the sand forming a structural skeleton and a matrix dominated by clay was examined. The soil characteristics changed dramatically at a given fines content which was dependent on water contents of clay. Initial shear moduli are presented for materials varying from sand to clay with various fines contents and water contents of clay. For material in which sand particles formed the skeleton the stiffness was dependent on the void ratio even if the fines content was identical. In the soil with a clay matrix there was a unique shear stiffness which varied with fines content. A relationship was established for the material with a sand skeleton between equivalent granular void ratio, initial shear modulus and water contents of clay.
An incident of rockfall may trigger serious damage to the safety as well as the after-the-event maintenance of railway transportation. In an attempt to minimize such damage caused by rockfall incident, the railway companies regularly in spect the concerned slopes along the railway, and take necessary measures. In the current practice, however, it is very difficult to make a full control of slopes in danger spreading over the wide area due to the limited human and financial resources. Accordingly, it is urgently needed for the railway firms to establish cost-effective as well as reliable system for the slope management. A risk map based on the impact statement of rockfall to railway track is of great use for not only enhancing the efficiency of slope inspection, but also planning the disaster prevention of railway. In this paper, a methodology for establishing a risk map by considering the impact statement to railway truck in a quantitative manner is proposed. In so doing, the rockfall movement on a slope was numerically simulated in match with each categorized type of slopes. The applicability of this proposed method for the slope management practice is examined based on a number of case histories.
Achievement of good resultant tunnel profile due to controlled contour blasting (CCB) in tunnel excavation has been of great importance for reduction of required cost. For this purpose, a new CCB technique was developed and has been in practical use, which applies unloaded large circular boreholes called guidehole having twice the diameter of charge hole and sets these guideholes between contour charge holes. This paper numerically investigated influence of the guidehole diameter on smoothness of resultant fracture plane in case of blasting with one free face. First we conducted stress analyses around guidehole walls for various borehole pressure wave forms applied in charge hole and showed that the stress concentration level was dependent on the guidehole diameter. Then we conducted dynamic fracturing process analyses considering heterogeneity of rock mass. We showed that the application of guidehole with larger diameter was effective for achieving smoother resultant fracture plane and discussed its mechanism in detail.
In the Tokyo International Airport (Haneda Airport), a new runway named "D-runway" was planned and constructed from March 2007 to October 2010. Because some part of the D-runway is located in a river mouth, a hybrid structure consisting of piled pier and reclamation fill was adopted. In the reclamation section, not only the ground improvement technologies (SD, CPD and CDM) but also the new developed construction materials (pneumatic mixing cement treated soil and air-foam treated lightweight soil) were utilized. This technical report describes the outline of the project, ground investigation, and design of the D-runway structure, from a geotechnical point of view.
Japanese design standard for port and harbor facilities was revised in 2007, modifying the method used to calculate the horizontal seismic coefficient, kh. The comprehensive change of the method indicates that the quay walls designed by the previous standard could be lack of earthquake resistance in terms of the current standard. In the present study, the coefficients, kh, calculated by the two standards were compared for the existing quay walls constructed in Kanto area, Japan. In addition, the factors that affected the relationship of two types of coefficients, kh, were identified by means of multiple regression analyses. Only 16 % of the current standard of kh exceeded the previous standard of kh. According to the multiple regression analyses, the ratio of two types of coefficients, kh, tended to increase in the quay walls which were located in a specific port and had the large wall height and the small importance factor.