In-situ measurement and analysis of freezing pressure of vertical shaft lining in deep alluvium

In order to thoroughly investigate the load of outer shaft lining, in-situ measurements on freezing pressure of vertical shaft lining are carried out during boring with freezing method sinking in deep alluvium in Juye coalfield. The in-situ measurements reveal that the maximum freezing pressure Pmax generally approches, even exceeds the permant horizontal ground presure P0 （estimitated according to the heavy liquid formulation）; the average value of Pmax/P0 is 1.08. The freezing pressure increases sharply within 15 d after the outer shaft is cast, in more than 57%⁶8% of the total strata, the freezing pressure P（t） at 7, 10, 14 d, reaches 72%, 77%, 81% of Pmax respectively. It is indicated that the accumulation of frost heave pressure inside and outside the ice wall is the ultimate reason that the freezing pressure usually exceeds the permant horizontal ground pressure. Consequently, characteristic value of the load （i.e., freezing pressure） of outer shaft lining should be assumed to be equal to the permant horizontal ground pressure, meanwhile, proper measures shoud be taken to reduce the frost heave pressure so as to reduce freezing pressure. Further more, the compressive strength of outer shaft lining at 7, 10, 14 d, should respectively reach 80%, 85%, 90% of its design value so as to guarantee the safety of outer shaft lining during the early period.