岩石の凍上に関する基礎的研究―岩石の内部構造，物性値の比較を基にした凍上メカニズムの解明―

Abstract

Our research was carried out based on comparison of the internal structure and the physical properties of rock in order to understand the mechanism of frost heave.We conducted frost heave tests on 5 types of rocks to understand the frost susceptibilityof rock. Ohya tuff, Kimachi sandstone, Noboribetu soft rock and Maruseppu tuff formed frost heave. Sapporo soft rock only did not occur frost heave. From these test results, the former were classified as frost susceptible while the latter was classified as non frost susceptible.Our research focused on the internal structure and the physical properties of rock. Permeability test and gas adsorption test by Bet method were conducted to understand internal structure of rock. And we compared the physical properties of frost susceptible rock and non frost susceptible rock. Pore size distribution, mineral composition, and strength in dry and wet condition etc. were measured. These measurements clarified certain differences between frost susceptible rock and non frost susceptible rock.Main results obtained in our research are summarized as follows:(1) Frost susceptible rock has a large surface area. A larger surface area enables a rock to hold a higher amount of unfrozen water on the surface while freezing, which means a smoother supply of water for ice lens formation and thus leading to a higher frost heave rate.(2) Non frost susceptible rock has a higher permeability than frost susceptible rock.(3) Water penetration in frost susceptible rock is more restricted due to the smaller pore radii than in non frost susceptible rock, which has greater pore radii. The permeability of rocks depends on the pore radii.(4) In the case of rock, which has a larger surface area or higher clay mineral/zeolite content, the tensile strength in wet condition is lower than in dry condition.