Engineering geological characterization of low strength anisotropic rocks in the Himalayan region for assessment of tunnel support

Bhasin, Rajinder; Barton, Nick; Grimstad, E.; Chryssanthakis, P.

doi:10.1016/0013-7952(95)00055-0

Cited by 26 publications

(5 citation statements)

References 6 publications

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“…Therefore, joint directions of the rocks could not be further studied. (Bhasin et al, 1995;Desai and Salami, 1987;Gurocak et al, 2012;Saroglou et al, 2004;Shea Jr and Kronenberg, 1993;Yilmaz, 2009) or prismatic specimens (Ramamurthy et al, 1993;Singh et al, 2002;Tiwari and Rao, 2007). As a result of the challenges in obtaining natural intact rock cores of suitable lengths, and also due to the friability of the in-situ rock, it was not practically possible to ascertain the anisotropy of the rock mass.…”

Section: Proposed Methods Of Testing Reconstituting Rock Spoilsmentioning

confidence: 99%

Evaluation of Pipe-Jacking Forces Based on Direct Shear Testing of Reconstituted Tunneling Rock Spoils

Choo

Ong

2015

J. Geotech. Geoenviron. Eng.

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The installation of underground trunk sewer lines in the Tuang Formation of Kuching City, Malaysia utilized trenchless technology in the form of the pipe-jacking method. The evaluation of pipe-jacking forces mainly involves empirical models developed for soils, with rather limited considerations for drives through weathered rock. Therefore, a novel approach is proposed to evaluate strength parameters by reconstituting and subsequently shearing scalped tunneling rock spoils in the direct shear apparatus. The direct shear results are then applied to a well-established pipe-jacking force model, which considers arching theory. The outcomes indicate that the back-analyzed frictional coefficients, µ avg are not only reliable but also related to their surrounding geologies due to soil-structure interaction. This study also highlights the significance of lubrication and effect of rock arching in assessing jacking forces. The successful characterization of reconstituted tunneling rock spoils in this paper has shown potential use in assessing jacking forces during micro-tunneling works.

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Section: Proposed Methods Of Testing Reconstituting Rock Spoilsmentioning

confidence: 99%

Evaluation of Pipe-Jacking Forces Based on Direct Shear Testing of Reconstituted Tunneling Rock Spoils

Choo

Ong

2015

J. Geotech. Geoenviron. Eng.

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“…It is typically necessary to have intact rock core lengths or prismatic specimens in order to proceed with rock strength tests, such as the uniaxial compression strength test, point load test, Brazilian tensile test, triaxial test or shear wave velocity test (Bhasin et al, 1995;Gurocak et al, 2012;Ramamurthy et al, 1993;Saroglou et al, 2004;Shea and Kronenberg, 1993;Tiwari and Rao, 2007). However, the highly fractured Tuang Formation meant that it was difficult to attain sound rock core lengths, which subsequently created challenges in measuring the rock strength parameters.…”

Section: Introductionmentioning

confidence: 99%

Impact of highly weathered geology on pipe-jacking forces

Choo

Ong

2017

Geotechnical Research

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, Malaysia, 7·7 km of trunk sewer lines were constructed in the highly fractured, highly weathered Tuang Formation using a pipe-jacking method. The pipelines were founded at depths of up to 35 m below Kuching City, where the majority of the pipe-jacking activities would traverse the Tuang Formation. Jacking forces in highly fractured geology are not well understood as most jacking force models were derived for drives traversing soils. Therefore, a novel method was developed, whereby equivalent rock strength characteristics were interpreted from direct shear testing on reconstituted tunnelling rock spoils. Tangential peak strength parameters, c 0 t,p and e 0 t,p , were developed from the nonlinear behaviour of the reconstituted spoils and applied to a wellestablished jacking model to assess arching and development of jacking forces from four documented drives. The backanalysed parameters l avg and r EV were used to demonstrate that geology had significantly affected the development of jacking forces. The back-analysis of the studied drives was successfully validated through finite-element modelling. This research shows that the developed parameters c 0 t,p and e 0 t,p and the back-analysed parameters l avg and r EV can be reliably used to predict jacking forces in highly fractured, highly weathered geology.

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“…In situ stresses along the tunnel route have been measured by hydraulic fracturing and by overcoring techniques (Bhasin et al 1996). The following values were found for the principal stresses: cy~ =7.1 MPa, approximately parallel to valley cy2 = 5.9 MPa, vertical stress cL~=3.9 MPa, approximately normal to valley However, because of the general weakness of the rock mass in the region of the Daj Khad shear zone, it has been assumed that the rock mass cannot tolerate significant stress differences and that all three principal in situ stresses are equal.…”

Section: Practical Examplementioning

confidence: 99%

Putting numbers to geology—an engineer's viewpoint

Hoek¹

1999

QJEGH

141

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Assigning numbers to geology requires a delicate balance between the commonly held opinion that geology cannot be quantified and the over-optimistic view that every physical quantity can be described in precise mathematical terms. In reality, many geological characteristics cannot be quantified precisely and intelligent guesses based upon experience and logical arguments are the best that can be hoped for.This paper explores the processes used to make some of these guesses and describes how the results are then applied to engineering design. It is shown that, with care, rational engineering decisions can be made in spite of the limitations of the input data. In recent years the development of computer hardware and software has made it much easier to investigate the influence of ranges of values for each of the input parameters. However, care has to be taken that the design is driven by sound geological reasoning and rigorous engineering logic rather than by the very attractive images that appear on the computer screen.

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Engineering geological characterization of low strength anisotropic rocks in the Himalayan region for assessment of tunnel support

Cited by 26 publications

References 6 publications

Evaluation of Pipe-Jacking Forces Based on Direct Shear Testing of Reconstituted Tunneling Rock Spoils

Evaluation of Pipe-Jacking Forces Based on Direct Shear Testing of Reconstituted Tunneling Rock Spoils

Impact of highly weathered geology on pipe-jacking forces

Putting numbers to geology—an engineer's viewpoint

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