SEGREGATION FREEZING OBSERVED IN WELDED TUFF BY OPEN SYSTEM FROST HEAVE TEST Akagawa, Satoshi, Goto, Shigeru and Saito, Akira Shimizu Corporatlon, Tokyo,Japan

SYNOPSIS Segregation freezing that results in ice lens growth is o~served du~i~g freezing in saturatéd and unsaturated porous rocks. The ~orous rock heaves ~n a way s~m~lar to soil frost heaving, cracking the rock, which has the tens1le strength of 1.~ MPa. ,The heave susceptibility of the rock was found to be lower than that of frost-suscept1ble s07l: however, tbe rest of the heaving properties appear to be simil~r. ~lmost the same segreg~t10n temp;ratures at which the f·inal ice lens segregates are obta~ned 1n two t~sts fro~ ~he 1ce lenses location and temperature profiles, regardless of the water satu~at10n cond1t10n of 9~ and 10?%. However, the heave and water intake properties seem to differ w1th,t~e.water saturat70n cond1tion. The growth of ice lenses in a porous rock reflects the poss1b1l1ty of weather1ng by segregation freezi~g during rock freezing. 0 I).t

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INTRODUCTION

FROST HEAVE TEST

Extensive studies of the weathering of rocks due to freeze-thaw cycles have been conducted in the past: however, there has been no general agreement On a weathering process (White, 1976). In one special case of rocl, weathering, the frost shattering of a frozen porous rock was studied by Fukuda and Matuoka (1982): thedata showed a possibility of segregation freezing, which may have resulted in the growth of visible or invisible ice lenses in the rock. Their paper clearly demonstrated the existence of the pore-water pressure gradient in the unfrozen part of the unsaturated rock while freezing.

Test apparatus Frost heave tests were conducted with the apparatus shown a