Genesis of channel bank overhangs in the Niger Delta and analysis of mechanisms of failure

Abam, T. K. S.

doi:10.1016/s0169-555x(96)00010-4

Cited by 23 publications

(16 citation statements)

References 7 publications

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“…A cantilever failure will occur if any of the overhanging blocks have a safety factor of less than one (Process 4 in Figure 5). The two types of cantilever failure mechanisms applied in this study are described by Abam (1997).…”

Section: Cantilever Failurementioning

confidence: 99%

“…where C is the compressive strength per unit length (kN/m), H′ is the overhanging block height (m), γ is the unit weight of soil (kN/m 3 ), b is the overhanging block width (C(T z 2 )/2γH′) as determined by Abam (1997) and z c is the maximum depth of a tension crack (2C/γ tan(π/4 + ϕ/2)) (T z is the tensile zone length (m) and ϕ is the internal friction angle) based on the location of the overhanging block width (Terzaghi et al, 1996). However, the tension crack depth for this study was assumed to be 0·5 of the overhanging block height because the ratio of tension crack depth to overhanging block height (0·3-0·7) does not typically change the factor of safety by more than 10% (Thorne and Abt, 1993).…”

Section: Cantilever Failurementioning

confidence: 99%

“…based on shear and beam failure mechanisms) (Abam, 1997;Thorne and Tovey, 1981); tensile failure was omitted because such failures have rarely been observed along actual rivers (Darby et al, 2007). A cantilever failure will occur if any of the overhanging blocks have a safety factor of less than one (Process 4 in Figure 5).…”

Section: Cantilever Failurementioning

confidence: 99%

“…Moreover, estimations of the failure plane angle and tension crack depth have been analysed using a combination of field and experimental data (Taghavi et al, 2010). Only a few studies have applied stability analyses based on the safety factor of the portion with cantilever failure, from which three types of possible cantilever failure mechanisms -shear, beam and tensile failures -have been defined (Abam, 1997;Thorne and Tovey, 1981).…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Cantilever failure investigations for cohesive riverbanks

Patsinghasanee¹,

Kimura²,

Shimizu³

et al. 2017

Proceedings of the Institution of Civil Engineers - Water Manag

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Section: Cantilever Failurementioning

confidence: 99%

Section: Cantilever Failurementioning

confidence: 99%

Section: Cantilever Failurementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Cantilever failure investigations for cohesive riverbanks

Patsinghasanee¹,

Kimura²,

Shimizu³

et al. 2017

Proceedings of the Institution of Civil Engineers - Water Manag

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show abstract

“…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%

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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Downstream change in river bank erosion rates in the Swale-Ouse system, northern England

et al. 1999

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Abstract:Few studies have considered downstream changes in bank erosion rates and variability along single river systems. This paper reports some preliminary results of an intensive and direct ®eld monitoring exercise of bank erosion rates on 11 sites along 130 km of the 3315 km 2 Swale-Ouse river system in northern England over a 14 . 5 month period. Data were collected at active sites using grid networks of erosion pins read at c. 18±30 day intervals and bank-line resurveys. Erosion rates were relatively high for a river of this scale: spatially averaged bank erosion magnitudes over the 14 . 5 months varied from 82 . 7 mm to 440 . 1 mm, although at one highly mobile reach retreat of 1760 mm was recorded over 4 months. Bank erosion rates tended to peak in mid-basin, possibly because of an optimum combination there of high stream powers and erodible bank materials, as predicted theoretically by Lawler (1992Lawler ( , 1995. The piedmont (upland±lowland transition) zone was especially active. Graphical erosion representations for speci®c periods, however, showed that bank retreat was often highly localized within individual sites. Strong seasonal variations in erosion rate were also observed with a signi®cant winter (December±March) peak. A novel ®nding, however, was the apparent downstream increase in the length of the erosion`season', with measurable retreat occurring at the lower sites from September to July. This is interpreted as a re¯ection of a richer mix of bank erosion processes at the downstream sites, where mass failure,¯uid entrainment and weathering processes are all active, with each process group having its own, but overlapping, temporal (seasonal) domain.

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Genesis of channel bank overhangs in the Niger Delta and analysis of mechanisms of failure

Cited by 23 publications

References 7 publications

Cantilever failure investigations for cohesive riverbanks

Cantilever failure investigations for cohesive riverbanks

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

Downstream change in river bank erosion rates in the Swale-Ouse system, northern England

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