A series of pre-bored pressuremeter tests (PMT) were performed in relatively young, weak rock deposits at several test sites in Taiwan. Equipment used included the Ménard type tri-cell pressuremeter and Cambridge high-pressure dilatometer. The test data were interpreted using some of the existing empirical and a newly developed analytical procedure. According to the interpretations of PMT data, the tested weak rock should behave as a highly overconsolidated cohesive material. This is contrary to some of the available laboratory experimental results. A 3-surface numerical scheme has been developed to simulate pressuremeter expansion in weak rock with unload-reload cycles. Preliminary results have indicated that the numerical scheme is capable of capturing the important features of pressuremeter expansion in a weak sandstone.