The purpose of the present investigation is to show analytically the existence of the Fenner-Pacher curve. This has been fully achieved by the distinct element method of a new model of tunneling.
The model ground consists of about 400 equal circle elements in regular array and a larger circle element of a tunnel (or circular closed lining) in the center of the array. This ground is subjected to a given initial vertical load and lateral load, and the tunneling is simulated by the decrescent of stiffness and weight of the tunnel element.
From the result it becomes clear that there are three typical characteristic curves due to the initial ground conditions: the elasto-plastic type showing continuous decrease of bearing load
P with increase of deformation
UD, the Fenner-Pacher type having
Pmin and a stable decrescent branch of
P with increase
UD, and the lateral-flow type showing sudden increase of
P and/or
UD after large and unstable
Pmin.
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