The present paper is a complement and extension of the theoretical pipe uplift theory developed by the authors (Foriero and Ladanyi, 1995). A comparison of the theoretical pipe peak-uplift-resistance with measurements from the Nixon and Hazen (1993) tests is carried out. The present theory shows a good agreement with the measured values of peak resistance and confirms that a gap forms below the pipe as it displaces upward. The theory is, however, limited to deep burial of the pipe, with no ground surface effects. Moreover, at sufficiently high upward displacement rates cracks are produced in the frozen soil. In view of this, a theoretical assessment of tension-fractured and compression-crushed zones above the upward moving pipe reveals an important drop in peak uplift resistance at increasing upward displacement rates.

INTRODUCTION

A problem of major concern in frost-pipeline interaction is the uplift resistance to upward motion of the pipe offered by the frozen soil. A low uplift resistance produces a gradual pipe heave near an interface between two unfrozen soils of different heave potentials. In this case, strains and curvatures induced in the pipe are negligible. If a transition occurs between frozen and unfrozen soils, the unfrozen soil may be capable of large frost heave. In such a case strains and curvatures in the pipe may become important (Fig. I). To date, the uplift resistance side of the transition has received considerably less attention than the frost heave side. Except for the studies carried out by Nixon et al.(1984, 1990), Nixon and Hazen (1993) and Foriero and Ladanyi (1995), most of the work has focused on longitudinal differential frost heave effects (Ladanyi and Shen (1993); Nixon et al. (1984); Rajani and Morgenstern (1992, 1993a,1993 b). Yet, as just mentioned, a major factor in frost heave-pipeline interaction analysis is the uplift resistance sustained by the pipe on the uplift-resistant side of the transition.

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