Effect of the development of notches and tension cracks on instability of limestone coastal cliffs in the Ryukyus, Japan

Kogure, Tetsuya; Aoki, Hiroo; Maekado, Akira; Hirose, Tsutomu; Matsukura, Yukinori

doi:10.1016/j.geomorph.2006.02.012

Cited by 71 publications

(62 citation statements)

References 9 publications

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“…We found cliff collapses having a failure mode different from those of Maekado (1991) and Kogure et al (2006) at a range of low coastal cliffs in Kuro-shima, one of the Ryukyu Islands. Collapses in Kuro-shima have a horizontal failure surface.…”

Section: Introductionmentioning

confidence: 49%

“…The dry bulk density is 1·89-2·56 Mg cm −3 according to Shinjo and Nakamura (1975) and 1·72-2·45 Mg cm −3 according to Kogure et al (2006), and the uniaxial compressive strength (UCS) is 6·1-59·2 MPa (5 cm diameter cylinder of height 10-12 cm, Shinjo and Nakamura, 1975) and 3·5-30·5 MPa (square pillar: 5 × 5 × 10 cm, Kogure et al, 2006). Kogure et al (2006) determined the effect of scale on the UCS of Ryukyu Limestone and found that the UCS decreases as the specimen size increases. They also found equations to estimate the rock mass strength taking into account the scale effect; for example, the tensile strength S t (MPa) of a square pillar with square side d (cm) can be modeled by the equation:…”

Section: Geological and Lithological Settingmentioning

confidence: 94%

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Critical notch depths for failure of coastal limestone cliffs: case study at Kuro‐shima Island, Okinawa, Japan

Kogure

Matsukura

2010

Earth Surf Processes Landf

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Development of a notch at the base of a cliff reduces cliff stability and often induces a collapse. Pleistocene limestone coastal cliffs of elevation 5 m in Kuro-shima, Ryukyu Islands, have a prominent notch with a depth of 3-4 m at their bases. Around these coastal cliffs, collapses different from previous studies of cliff collapses in the Ryukyu Islands were found; collapses in Kuro-shima have a horizontal failure surface. The horizontal failure surface, situated at the height of the failure surface corresponding to the retreat point of the notch, is bounded by vertical joints cutting the whole cliff and the reef fl at in front of the cliff. Two types of horizontal failure surface were found, triangular and quadrangular; the distinction appears to depend on the angle between the vertical joints and the front face of the cliff. Prior to collapse, these cliffs appear to have been separated from the adjacent cliffs by the development of vertical joints. Consequently, a cliff that will collapse can be identifi ed in advance; cliff instability is strongly dependent on the development of a notch. To study the effect of notch development on cliff collapse, the notch depth at which collapse occurs was calculated using stability analysis. Instability of a cliff increases with notch depth; collapse occurs at the horizontal failure surface when the ratio of the notch depth to the seaward length of the cliff is approximately 0·5-0·7 for a triangular failure surface, and 0·7-0·9 for a quadrangular failure surface.

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Section: Introductionmentioning

confidence: 49%

Section: Geological and Lithological Settingmentioning

confidence: 94%

Critical notch depths for failure of coastal limestone cliffs: case study at Kuro‐shima Island, Okinawa, Japan

Kogure

Matsukura

2010

Earth Surf Processes Landf

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“…At some locations, the shore platform elevation allows wave attack at all tide stages. Cliff undercutting at the cliff base from wave action is often present and can result in cliff instability, as at other cliffs (Hampton, 2002;Kogure et al, 2006;Young and Ashford, 2008;Budetta, 2010). Cliff failures in the Point Loma Formation generally occur as rock falls, block falls, and topples (Varnes, 1978).…”

Section: Geologymentioning

confidence: 99%

Short-term retreat statistics of a slowly eroding coastal cliff

Young

Guza

O’Reilly

et al. 2011

Nat. Hazards Earth Syst. Sci.

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Abstract. The frequency, spatial distribution, and dimensions of coastal cliff retreats, a basic statistic underlying cliff top hazard assessment, are presented for 7.1 km of unprotected and slowly retreating coastal cliffs near Point Loma in San Diego, California, US. Using 8 airborne light detection and ranging (lidar) surveys collected over 5.5 years, 130 individual cliff edge failures (primarily rockfalls, block falls, and topples) were detected. Footprint areas varied from 3 to 268 m 2 , maximum landward retreats from 0.8 to 10 m, and alongshore lengths from 2 to 68 m. The failures with the largest landward retreats were also relatively long, and 13% of the slides accounted for 50% of the lost cliff area over the study period. On this short (5.5 years) time scale, "no change" was the most common observation (84% of the cliff edge). Probability distributions of non-zero cliff retreat during each time interval usually had a single peak between 1 and 2.5 m. Intervals with high mean retreat had elevated numbers of failure in all class sizes, and also contained the largest individual retreats. Small and medium slides tended to reoccur preferentially (relative to randomly) near previous small and medium slides, forming short-term hot spots, while large slides were less likely to reoccur near previous large slides. Cumulative distributions of landslide failure parameters (area, mean retreat, maximum retreat, and length) follow an inverse power-law for medium to large size events, similar to previously reported distributions of coastal and inland landsliding.

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“…To test this hypothesis, as well as the potential of gravitational collapses of rock blocks on the cliff, we conducted a stability analysis on the cliff face by using a cantilever beam model that incorporates notch development beneath a cliff and associated stress distribution by rotational moment inside the cliff (Figure 4) [35][36][37][38][39]. The application of a cantilever beam model for waterfall cliff face has also been verified in the case of Niagara Falls [22].…”

Section: Stability Analysis Model Of Undercut Cliffmentioning

confidence: 99%

“…If a vertical crack length propagating from the upper surface of the cliff is introduced, the critical notch length is then represented as [39]   …”

Section: Stability Analysis Model Of Undercut Cliffmentioning

confidence: 99%

Stability Analysis of Cliff Face around Kegon Falls in Nikko, Eastern Japan: An Implication to Its Erosional Mechanisms

Hayakawa¹

2013

IJG

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A waterfall highlights the locus of active fluvial erosion of bedrock, and its mechanism has been the subject of several studies; however, erosional processes remain to be clarified for specific rock structures composing a waterfall. Herein, the detailed morphology of cliffs around a waterfall is examined by a terrestrial laser scanning (TLS) approach to analyze erosional processes occurring in the cliffs. The study site is Kegon Falls in Japan, which has a vertical drop of surface water from the top of its cliff and groundwater outflows from its lower portion. The entire cliff is mostly overhanging and minor rockfalls are often observed. The latest major rockfall occurred in 1986, causing an approximate 8-m upstream shift of the waterfall lip. From the point cloud obtained by TLS measurement, a digital elevation model on a vertical plane was generated, and cross-sectional profiles were extracted. A distinct 5-to 10-m depression was found at the bottom of the upper andesite layer of the waterfall cliff, which appears to have been formed by freeze-thaw and wet-dry weathering following the upstream shift of the surface water drop. Stability analysis of the waterfall cliff with an undercutting notch indicates that the igneous rock composing the cliff is sufficiently strong to maintain its current overhanging shape and that catastrophic collapse of the entire waterfall face rarely occurs. Following the formation of the depression, the upper cliff face appears to have been gradually eroded by gravitational collapses of relatively small blocks bounded by columnar and platy joints.

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Effect of the development of notches and tension cracks on instability of limestone coastal cliffs in the Ryukyus, Japan

Cited by 71 publications

References 9 publications

Critical notch depths for failure of coastal limestone cliffs: case study at Kuro‐shima Island, Okinawa, Japan

Critical notch depths for failure of coastal limestone cliffs: case study at Kuro‐shima Island, Okinawa, Japan

Short-term retreat statistics of a slowly eroding coastal cliff

Stability Analysis of Cliff Face around Kegon Falls in Nikko, Eastern Japan: An Implication to Its Erosional Mechanisms

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