Temperature effects on the mechanical and environmental behavior of the ground

2020 Fiscal Year Final Research Report

• Project/Area Number: 18K13828
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 22030:Geotechnical engineering-related
• Research Institution: Kyoto University
• Principal Investigator: Takai Atsushi 京都大学, 地球環境学堂, 准教授 (30598347)
• Project Period (FY): 2018-04-01 – 2021-03-31
• Keywords: 温度効果 / 温度圧密 / 地盤環境 / コンシステンシー / 溶出試験 / 地盤改良

Outline of Final Research Achievements

Under the temperature condition of 10 to 50 Celsius, the plastic limit did not change significantly for any clay, but the liquid limit may decrease or increase with increasing temperature. These tendencies and the magnitude of the change can be determined probably by smectite content and sedimentary environment.
The changes in the consolidation coefficient focusing only on the viscosity coefficient of the pore water can be calculated to 0.87, 1.27, and 1.65 times at 17, 35 and 50 Celsius, respectively, as compared with the case of 23 Celsius. These values match well with the change in coefficient of consolidation obtained from laboratory consolidation test, regardless of the type of clay.
From the results of the leaching test, the As leaching concentration of crushed shale rock was up to 10 times higher at 40 Celsius than at 20 Celsius. It is probably because the desorption of colloidal particles containing aluminum was accelerated due to an increase in temperature.

Free Research Field

環境地盤工学

Academic Significance and Societal Importance of the Research Achievements

地盤温度を23℃から50℃に上昇させることで粘土の圧密係数が1.7倍程度に大きくなることから，適切に粘土地盤を加温できれば，完了までに数ヶ月要する粘土地盤の圧密期間を短縮でき，後続の工事を早期に着手できる。また，間隙水の粘性係数から，圧密係数の変化を概ね推定できる。
掘削岩石は盛土材として再生利用することが考えられるが，そのような浅層地盤では地盤深部に比べ地盤温度の日変動，季節変動が大きい。さらなる検討が必要であるが，本研究で得られた成果から，我が国の岩石に広く分布しているAsの溶出量は，温度変化に対して無視し得ないほど高くなることから，利用条件を考慮して適切に溶出リスクを評価する必要がある。