Hydrofracturing in situ stress measurements in Singapore granite

Zhao, Jun; Hefny, A. M.; Zhou, Yingxin

doi:10.1016/j.ijrmms.2005.02.002

Cited by 34 publications

(16 citation statements)

References 10 publications

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“…In each hydraulic fracturing test, the fluid is injected into sealed off borehole intervals to induce and propagate hydraulic fractures in the rock mass. The stress regime in the rock mass can be determined from the pressure data during the hydraulic fracturing test (Zhao et al 2005). The distribution of the maximum and minimum horizontal in situ stress was obtained from ten hydraulic fracturing tests in one vertical borehole at depths between 80 and 170 m below the sea bottom.…”

Section: Site Investigation For the In Situ Stressmentioning

confidence: 99%

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Rock Cavern Stability Analysis Under Different Hydro-Geological Conditions Using the Coupled Hydro-Mechanical Model

et al. 2015

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Rock cavern stability has a close relationship with the uncertain geological parameters, such as the in situ stress, the joint configurations, and the joint mechanical properties. Therefore, the stability of the rock cavern should be studied with variable geological conditions. In this paper, the coupled hydro-mechanical model, which is under the framework of the discontinuous deformation analysis, is developed to study the underground cavern stability when considering the hydraulic pressure after excavation. Variable geological conditions are taken into account to study their impacts on the seepage rate and the cavern stability, including the in situ stress ratio, joint spacing, and joint dip angle. In addition, the two cases with static hydraulic pressure and without hydraulic pressure are also considered for the comparison. The numerical simulations demonstrate that the coupled approach can capture the cavern behavior better than the other two approaches without the coupling effects.

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Section: Site Investigation For the In Situ Stressmentioning

confidence: 99%

“…In addition, both the hydraulic fracturing test and laboratory experiments were carried out by Zhao and his colleagues in 2005 (Zhao et al 2005) to obtain the in situ stress conditions for the underground granite in Singapore. From their observations, the in situ stress ratio is in the range of 2-6.…”

Section: Site Investigation For the In Situ Stressmentioning

confidence: 99%

Rock Cavern Stability Analysis Under Different Hydro-Geological Conditions Using the Coupled Hydro-Mechanical Model

et al. 2015

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“…In Figures 2-5, the numbers in parenthesis indicate: (1) Finland, Scandinavia (Hast, 1958); (2) Canada (Linder and Haipern, 1978); (3) Cornwall, UK (Pine et al, 1983); (4) USA (Linder and Haipern, 1978); (5) Australia; (6) Japan (Kanagawa, 1986); (7) Singapore (Zhao et al, 2005). The plane numbers represent: 1.…”

Section: Variation Of Stress Magnitudesmentioning

confidence: 99%

“…That is, in shallow depths, the horizontal stress is dominant and values of λ are larger than those of k for the same point. For example, in Bukit Timah granite, Singapore, the λ is over 3 times the vertical stress (Zhao et al, 2005).…”

Section: Variation Of Stress Magnitudesmentioning

confidence: 99%

“…Tensile strength (σ t ') of rock mass from the borehole tests via the hydro-fracturing technique and the tensile strength of rocks (σ t ) from laboratory tensile testing using the Bra- (Hast, 1958); (2) Canada (Linder and Haipern, 1978); (3) Cornwall, UK (Pine et al, 1983); (4) USA (Linder and Haipern, 1978); (5) Australia; (6) Japan (Kanagawa, 1986); (7) Singapore (Zhao et al, 2005). The plane numbers represent that 1-Guangzhou pumped power station (Liu et al, 1990), 2-Three Gorges project (Liu and Xiao, 1989), 3-Jinzhou (Hou et al, 2006), and 4-Daya Bay .…”

Section: Variation Of Stress Magnitudesmentioning

confidence: 99%

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From in situ stress and discontinuities to the strength of granites: comparison and case study

et al. 2008

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From in situ stress and discontinuities to the strength of granites: comparison and case study ABSTRACT: The distinctive weathering profile and discontinuity of granites, dipping slightly at shallow depths and steeply in larger depths, are regarded as being due to their physical and geo-mechanical properties. This paper compares vertical stress (Sv) and overlain weight (γh) drawn from different kinds of in situ stress measurements, as well as coefficients of lateral stress. Stress trends are connected with discontinuities (joints and dykes), which reveal their relationships in space and dip angles of joints and dykes are compared in space, together with shear plane plunges and the strength of rocks from laboratory tests. As a result, it was found that the relict structural geostress contributes to maximum horizontal stress, especially at shallow depths. The most common feature is the high coefficient of lateral stress, which is mostly attributed to unloading in shallow depths and stress concentration at a certain depth after the erosion of overlain beds and the exposure of granites at the ground surface. Therefore, the weathering profiles and weathered capsule of granites could be interpreted from this viewpoint. One of the two main features of this paper is the connection of the extraordinary values of the lateral coefficient of in situ stress with unloading and the typical weathering profile at shallow depths. Another is the comparison of the shear stress and strength from in situ and laboratory tests, with a series of data from the same location and depth.

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A new global database to improve predictions of permeability distribution in crystalline rocks at site scale

2017

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A comprehensive worldwide permeability data set has been compiled consisting of 29,000 in situ permeabilities from 221 publications and reports and delineating the permeability distribution in crystalline rocks into depths of 2000 meters below ground surface (mbgs). We analyze the influence of technical factors (measurement method, scale effects, preferential sampling, and hydraulic anisotropy) and geological factors (lithology, current stress regime, current seismotectonic activity, and long‐term tectonogeological history) on the permeability distribution with depth, by using regression analysis and k‐means clustering. The influence of preferential sampling and hydraulic anisotropy are negligible. A scale dependency is observed based on calculated rock test volumes equaling 0.6 orders of magnitude of permeability change per order of magnitude of rock volume tested. Based on the entire data set, permeability decreases as log(k) = −1.5 × log(z) − 16.3 with permeability k (m2) and positively increasing depth z (km), and depth is the main factor driving the permeability distribution. The permeability variance is about 2 orders of magnitude at all depths, presumably representing permeability variations around brittle fault zones. Permeability and specific yield/storage exhibit similar depth trends. While in the upper 200 mbgs fracture flow varies between confined and unconfined, we observe confined fracture and matrix flow below about 600 mbgs depth. The most important geological factors are current seismotectonic activity (determined by peak ground acceleration) and long‐term tectonogeological history (determined by geological province). The impact of lithology is less important. Based on the regression coefficients derived for all the geological key factors, permeability ranges of crystalline rocks at site scale can be predicted. First tests with independent data sets are promising.

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Hydrofracturing in situ stress measurements in Singapore granite

Cited by 34 publications

References 10 publications

Rock Cavern Stability Analysis Under Different Hydro-Geological Conditions Using the Coupled Hydro-Mechanical Model

Rock Cavern Stability Analysis Under Different Hydro-Geological Conditions Using the Coupled Hydro-Mechanical Model

From in situ stress and discontinuities to the strength of granites: comparison and case study

A new global database to improve predictions of permeability distribution in crystalline rocks at site scale

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