| Summary: | 碩士 === 國立中央大學 === 應用地質研究所 === 83 === Fault zones are the weak zones resulted from extreme shearing
disturbance in the strata, and fault gouges of different
thickness are often contained. With the influence of ground
water and stress state on its properties, fault gouges always
causes disasters in the process of engineering construction.
There exists very much close relationship between such
disasters and the the properties of high swelling pressure and
gradually softening of the fault gouge as a result of
absorption of moisture and stress relief. However, that the
reason why there exists characteristics of high swelling in the
fault gouge of major fault zones and what the main causes are
is really concerned. Due to not containing pronounced expansive
clay minerals and the characteristics of overconsolidation and
diagentic bond, the experienced rules commonly used in the
evaluation of swell potential of expansive soil is not complete
applicable to the fault gouge samples in this research. The
record of unloading process in the consolidation test reveals
that the higher the overconsolidation ratio(OCR), the higher
the secondary swelling index, and the lower the coefficient of
swelling. The phenomenon of secondary swelling is more
pronounced with time passing. It may be deduced that high OCR
occurs in the fault gouge owing to unloading condition during
tunnel excavation through major fault zones under high
overburden pressure. Therefore, the secondary swelling is more
pronounced with time passing. Although nothing particular is
observed in the short term, the tunnel is gradually squeezed
and deformed to the end of destruction in the long term. The
reason why the value of c'' is different between the two fault
gouges described above is possibly related to the degree of
weathering, and φ'' is possibly related to the strain rate and
the number of foliation in the same sample size.
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