Geoscience Research Laboratory Co.

Yamato, Japan

Geoscience Research Laboratory Co.

Yamato, Japan
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Jiang Y.,Nagasaki University | Jiang Y.,Shandong University of Science and Technology | Wang X.,Qingdao Technological University | Li B.,Shaoxing University | And 3 more authors.
Soils and Foundations | Year: 2016

Fiber-reinforced plastic (FRP) is a practical alternative construction material that has been extensively adopted in the reinforcement of concrete structures. The reinforcing effect of FRP grids needs to be quantitatively estimated when the grids are applied to degraded tunnel linings to assist with the maintenance design. In the present study, the reinforcing effect of FRP grids embedded in Polymer Cement Mortar (PCM) shotcrete (the FRP-PCM method) on degraded tunnels was estimated. Laboratory direct shear tests and bending tests were carried out on specimens reinforced with various grades of FRP grids to obtain the mechanical properties of the bonding surfaces between the PCM and the concrete reinforced by FRP grids. The bending test results showed that the bearing capacity of beams reinforced by FRP grids subjected to bending loads improved by around 40%. A numerical modeling of the reinforced tunnels by the FRP-PCM method was performed using the properties obtained from these laboratory tests to investigate the reinforcing performance of the FRP-PCM method on degraded tunnel linings. Numerical models with different loosening pressures acting on the tunnel lining, ground classes, degrees of lining deterioration, and degrees of tunnel health were considered, and the suitable conditions under which the application of the FRP-PCM method could effectively reinforce tunnel linings were proposed. © 2017.


Ishikawa T.,Hokkaido University | Tokoro T.,Tomakomai National College of Technology | Sato M.,Geoscience Research Laboratory Co.
15th Asian Regional Conference on Soil Mechanics and Geotechnical Engineering, ARC 2015: New Innovations and Sustainability | Year: 2015

This paper presents numerical simulations on frost heave phenomenon observed at the earth structures and pavement structures using a coupled thermo-hydro-mechanical (THM) FE analysis, which can consider the change in deformation-strength characteristics and water retention-permeability characteristics due to freeze-thaw actions, and can reproduce frost-heave of soils under unsaturated conditions based on the results of frost heave tests. In order to evaluate the influences of freeze-thaw action on the interaction between frost-susceptible soil ground and structures quantitatively, a series of numerical simulations for cut slope and pavement structure subjected to freeze-thaw actions were performed. As the results, it was revealed that the coupled FE analysis employed in this study has a sufficient applicability to the precise prediction for the frost-heave behavior of soil ground, and that the frost-heave behavior has a considerable influence on the deformation and failure of earth structures in terms of the deformation and stress state of structures by examining the relation between frost heave and frost penetration depth.


Fukuda T.,Geoscience Research Laboratory Co. | Takahashi T.,East Nippon Expressway Company | Yamada H.,Konoike Construction Co. | Jiang Y.,Nagasaki University
Harmonising Rock Engineering and the Environment - Proceedings of the 12th ISRM International Congress on Rock Mechanics | Year: 2012

In the design phase of the tunnel, various mechanical constants and their distribution are estimated after comparing research and exploration results with rock mass classification. Based on the estimation, the support pattern is selected and appropriate materials are suggested by numerical analysis, if necessary. In this study, from the perspective of advanced observational construction, we describe the identification of rock physical properties by back analysis and the predictive analysis of long-term deformation of tunnel lining targeting on the tunnel with large deformation. As a result, the most appropriate support pattern was determined by identifying rock physical properties, and an example of long-term predictions of tunnel lining deformation could be presented. © 2012 Taylor & Francis Group, London.


Akiyama M.,Geoscience Research Laboratory Co. | Kawasaki S.,Hokkaido University
Ecological Engineering | Year: 2012

We added calcium carbonate (CC) powder to a novel grout made from calcium phosphate compound (CPC-chem) to increase the ground strength improvement afforded by CPC-chem. We conducted the unconfined compressive strength (UCS) test and scanning electron microscopy (SEM) observation on test pieces cemented with CPC-chem and CC powder. The UCS of test pieces cemented with CPC-chem and CC powder was significantly higher than that of test pieces cemented without CC powder, and it reached a maximum of 209.7. kPa. The UCS of test pieces cemented with CC powder and deionized water was 12.5. kPa, which was similar to that of test pieces cemented with deionized water only (10. kPa). SEM observation revealed mesh-like and three-dimensional structures in the segment of the test piece cemented with CPC-chem and 1. wt% of CC, which showed UCS of over 200. kPa and the minimum axial strain rate among all cases in this study. These results suggest that the addition of CC powder significantly enhances the ground improvement afforded by CPC-chem. © 2012 Elsevier B.V.


Kawasaki S.,Hokkaido University | Akiyama M.,Geoscience Research Laboratory Co.
Soils and Foundations | Year: 2013

To improve the unconfined compressive strength (UCS) of a novel chemical grout composed of a calcium phosphate compound (CPC-Chem), we performed UCS tests and scanning electron microscopy (SEM) observations on sand test pieces cemented with CPC-Chem and four kinds of powders (tricalcium phosphate, TCP; magnesium phosphate, MgP; calcium carbonate, CC and magnesium carbonate, MgC) as seed crystals. The UCS of the CPC-Chem test pieces cemented with TCP and CC was significantly greater than that of the test pieces with no added powders. The UCS of the test pieces with TCP and CC additives exceeded the targeted value of 100 kPa and increased to a maximum of 261.4 kPa and 209.7 kPa for the test pieces with TCP and CC additives, respectively. Furthermore, the UCS of test pieces with 1 wt% or 5 wt% TCP and 1 wt% CC additives was maintained at a level exceeding 200 kPa for 168 days. SEM observations revealed net-like and three-dimensional structures in segments of test pieces cemented with 1 wt% or 5 wt% TCP and 1 wt% CC in CPC-Chem, which could have been the reason of the long-term stability of UCS (over 200 kPa for 168 days) observed in this study. These results suggest that the addition of TCP and CC significantly enhances the ground improvement afforded by CPC-Chem. © 2013 The Japanese Geotechnical Society.


Akiyama M.,Geoscience Research Laboratory Co. | Kawasaki S.,Hokkaido University
Engineering Geology | Year: 2012

To evaluate the potential utility of a new calcium-phosphate-compound (CPC)-based biogrout (CPC biogrout), we conducted unconfined compressive strength (UCS) tests and scanning electron microscope (SEM) observations of sand test pieces cemented with CPC biogrout. The CPC biogrout was produced using (1) soil extracts that contained microorganisms derived from one of two soils, which had different pH values, and (2) one of three amino acids or urea as a pH-increasing reactant. A temporal increase in pH was observed in slightly acidic soil by the addition of ammonia sources. On the other hand, there was no significant increase in pH in slightly alkaline soil except for that due to urea. In most cases, the UCS of the test pieces cemented with CPC biogrout produced using soil extracts from acidic soil along with an ammonia source was higher than that of the test pieces cemented with CPC biogrout produced without the addition of ammonia sources. SEM observation of test pieces with UCS of over 50. kPa showed the presence of whisker-like CPC crystals. These results suggest that CPC biogrout affords sufficient strength as a countermeasure for soil liquefaction and that amino acids can be used as new pH-increasing reactants for CPC biogrout. In addition, they suggest that either CPC biogrout or CPC chemical grout alone, or a combination of the two grouts, can be used depending on the various properties of grounds and soils. © 2012 Elsevier B.V.


Akiyama M.,Geoscience Research Laboratory Co. | Kawasaki S.,Hokkaido University
Engineering Geology | Year: 2012

Calcium phosphate compounds (CPCs) have unique physicochemical properties. As grout material, they afford many advantages such as adequate physical strength, self-setting property, pH dependence of precipitation, non-toxicity, and recyclability. To apply CPCs to the permeability control and reinforcement of ground soil and rock, we explored suitable conditions for in vitro CPC precipitation, conducted unconfined compressive strength (UCS) tests of Toyoura sand test pieces cemented by CPC, and carried out observations and elemental analysis of precipitated CPC crystals. Two kinds of phosphate stock solution and two kinds of calcium stock solution were used to prepare the reaction mixtures, and CPC precipitation was detected in all reaction mixtures. The volume of CPC precipitation in the reaction mixture increased as the pH rose from strongly acidic to around neutral. The UCS of Toyoura sand test pieces cemented by 1.5. M diammonium phosphate and 0.75. M calcium acetate tended to increase with time, reaching a maximum of 63.5. kPa after 14. days of curing. Conversely, the UCS of test pieces cemented by using calcium nitrate was below 20. kPa and showed no significant increase in strength. CPC precipitation with calcium nitrate induced the formation of plate-like crystals, whereas that with calcium acetate induced whisker-like crystals. Elemental analysis of the cemented test pieces showed that the distributions of phosphorus and calcium were similar. The results indicate the practical feasibility of using novel CPC grouts as chemical grouts because of their self-setting property, and as biogrouts because of their crystal structure and pH dependence of precipitation. © 2011 Elsevier B.V.


Kawasaki S.,Hokkaido University | Akiyama M.,Geoscience Research Laboratory Co.
International Journal of GEOMATE | Year: 2013

To employ calcium phosphate compounds (CPCs) in ground improvement measures such as the reinforcement of soil and rock, we examined suitable conditions for CPC precipitation and performed unconfined compressive strength (UCS) tests of sand test pieces cemented by CPC. Two types of phosphate stock solution and two types of calcium stock solution were used to prepare the reaction mixtures and CPC precipitation was confirmed in all reaction mixtures. The volume of CPC precipitation in the mixture increased as the pH rose from strongly acidic to around neutral. The UCS of sand test pieces cemented by 1.5 M diammonium phosphate and 0.75 M calcium acetate tended to increase with time, reaching a maximum of 87.6 kPa. The results indicate the practical feasibility of using unique and new CPC grouts as chemical grouts because of their self-setting property and as biogrouts because of the pH dependence of precipitation. © 2013, International Journal of GEOMATE.


Ishikawa T.,Hokkaido University | Kijiya I.,Hokkaido University | Tokoro T.,Tomakomai National College of Technology | Sato M.,Geoscience Research Laboratory Co.
Computer Methods and Recent Advances in Geomechanics - Proceedings of the 14th Int. Conference of International Association for Computer Methods and Recent Advances in Geomechanics, IACMAG 2014 | Year: 2015

This study proposes a new numerical model to simulate the Thermo-Hydro-Mechanical (THM) behavior of saturated and unsaturated soils suffered from one-dimensional freeze-thawing. First, a coupledTHM FE analysis, which can consider the change in deformation-strength and water retention-permeability characteristics due to freeze-thaw actions, was newly developed. It also can reproduce frost heave phenomenon of soils under saturated and unsaturated conditions based on the results of frost susceptibility tests. Subsequently, a series of numerical simulations on frost heave tests of a soil specimen was conducted by the proposed FE analysis, and the analytical results were compared with experimental results to examine the applicability of the coupled FE analysis. As the result, it was revealed that the coupled FE analysis proposed in this study has valuable advantages of excellent applicability to the precise prediction method for the thermal-hydro-mechanical behavior of frost-susceptible soils during freeze-thaw. © 2015 Taylor & Francis Group, London.


Kawasaki S.,Hokkaido University | Akiyama M.,Geoscience Research Laboratory Co.
Materials Transactions | Year: 2013

For the purpose of improving a novel grout composed of a calcium phosphate compound (CPC-Chem), we have conducted an unconfined compressive strength (UCS) test on samples cemented with CPC-Chem and tricalcium phosphate (TCP) powder. The UCS of these test samples was significantly larger than the UCS of the non-additive test samples. The UCS reached the targeted value of over 100 kPa, and after 28 days of curing, reached a maximum of 261.4 kPa. Additionally, the pH of the samples cemented with CPC-Chem and TCP powder was weakly acidic. These results suggest that the novel geotechnical method using a combination of CPC-Chem and TCP powder has the potential to be used as a non-contaminating and recyclable application, as a biogrout that uses microbial activity and for ground improvement because it satisfies the strength requirements for practical use. © 2013 The Japan Institute of Metals and Materials.

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