A review of the testing approaches in swelling rock conditions at three different institutions

Abstract

The swelling potential of weak rocks is crucial to assess in stability determinations of tunnels constructed for both infrastructure and hydropower. Among the institutions that are involved with extensive research on swelling rock material, the methodologies applied at three different European institutions are reviewed in this manuscript. XRD analysis and oedometer swelling tests are included as index tests at all three institutions whereby the adopted swelling test methodologies at all three institutions are grounded in the ISRM standards. Different mindsets in how to forecast the challenges related to swelling are, however, reflected in the boundary conditions of test procedures and the internal modifications on the test apparatus, the preparation procedure, and in the choice of specimen size/mass. This manuscript reviews the adopted methodologies and highlights the advantages and drawbacks on the testing approaches used. Two of the institutions rely on a general approach which is standardized, and the results are compared. It is highlighted that, both institutions have modified the ISRM standard and the methodologies represents two unique approaches. Institution 3 have a case-specific approach and no test data were available. However, the described methodology differs from the procedures at Institution 1 and 2. Important differences between the testing procedures are both discussed and exemplified by comparing the test results obtained from duplicate samples at two of the institutions.

Study on Expansion Characteristics and Expansion Potential of Gypsum Rock

“…The ultimate expansion force [13,14,39] is not only the most important index for judging the expansion potential of expansive soil but also the most important parameter for structural design. No matter the reason for the expansion, its ultimate expansion force corresponds to the same expansion potential grade; the mineral composition and expansion mechanism only affect the expansion rate and do not affect the expansion potential grade.…”

“…At present, expansive rocks are divided into two categories [13][14][15][16][17][18]: the first one is caused by chemical expansion reaction, the mechanism is complex, and the time is long (such as anhydrite and glauberite); the second one is caused by hydrophilic minerals, and the expansion of this type of rock is cyclically reciprocated under the action of water absorption and loss (such as mudstone and tuff) [19]. The main indicators for judging the expansion potential of expansive rocks include water content [20][21][22], viscous material content [9,15,[23][24][25], free expansion rate [25], ultimate expansion rate [26], dry saturated water absorption rate [27], and ultimate expansion force [9,25].…”

“…Huang et al [38] use environmental factors to guide machine self-learning to predict landslides. Therefore, in this paper, the free expansion rate test, the ultimate expansion rate test, the ultimate expansion force test, and the BET-specific surface area test were carried out on the gypsum rock from the Wuzhishan Tunnel; at the same time, based on the existing methods [13,14,18,30], the expansion potential of gypsum rocks can be quickly and accurately predict by combining the ultimate expansion rate and specific surface area indexes.…”