Integration of three-dimensional laser scanning with discontinuum modelling for stability analysis of tunnels in blocky rockmasses

Fekete, Stephanie; Diederichs, Mark S.

doi:10.1016/j.ijrmms.2012.08.003

Cited by 105 publications

(38 citation statements)

References 12 publications

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“…Evans 2005) or using discontinuum numerical modelling methods commonly used at the tunnel scale (e.g. Vardakos et al 2007;Fekete and Diederichs 2013). Similarly, a fracture density consisting of only parallel joints, rather than intersecting joint sets, should be analysed using discrete methods because of the anisotropic nature of the rock mass.…”

Section: Failure Criterion Input Parameter Considerationsmentioning

confidence: 99%

Estimating in situ rock mass strength and elastic modulus of granite from the Soultz-sous-Forêts geothermal reservoir (France)

et al. 2018

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Knowledge of the strength and elastic modulus of a reservoir rock is important for the optimisation of a particular geothermal resource. The reservoir rock for many geothermal projects in the Upper Rhine Graben, such as those at Soultz-sous-Forêts and Rittershoffen (both France), is porphyritic granite. High fracture densities (up to ~ 30 fractures/m) in this reservoir rock require that we consider the strength and elastic modulus of the rock mass, rather than the intact rock. Here we use uniaxial and triaxial deformation experiments performed on intact rock coupled with Geological Strength Index assessments-using the wealth of information from core and borehole analyses-to provide rock mass strength and elastic modulus estimates for the granite reservoir at Soultz-sous-Forêts (from a depth of 1400 to 2200 m) using the generalised Hoek-Brown failure criterion. The average uniaxial compressive strength and elastic modulus of the intact granite are 140 MPa (this study) and 40 GPa (data from this study and the literature), respectively. The modelled strength of the intact granite is 360 MPa at a depth of 1400 m and increases to 455 MPa at 2200 m (using our estimate for the empirical m i term of 30, determined using triaxial and tensile strength measurements on the intact granite). Strength of the rock mass varies in accordance with the fracture density and the extent and nature of the fracture infill, reaching lows of ~ 40-50 MPa (in, for example, the densely fractured zones in EPS-1 at depths of ~ 1650 and ~ 2160 m, respectively) and highs of above 400 MPa (in, for example, the largely unfractured zone at a depth of ~ 1940-2040 m). Variations in rock mass elastic modulus are qualitatively similar (values vary from 1 to 2 GPa up to the elastic modulus of the intact rock, 40 GPa). Our study highlights that macrofractures and joints reduce rock mass strength and should be considered when assessing the rock mass for well stability and rock mass deformation due to stress redistribution in the reservoir. We present a case study to demonstrate how a simple and cost-effective engineering method can be used to provide an indication of the in situ strength and elastic modulus of reservoir rock masses, important for a wide range of modelling and stimulation strategies. We recommend that the effect of macrofractures on rock mass strength and stiffness be validated for incorporation into geomechanical characterisation for geothermal reservoirs worldwide.

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Section: Failure Criterion Input Parameter Considerationsmentioning

confidence: 99%

Estimating in situ rock mass strength and elastic modulus of granite from the Soultz-sous-Forêts geothermal reservoir (France)

et al. 2018

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“…Terrestrial Laser Scanner (TLS) surveys and 3D Distinct Element Methods (DEMs) have been coupled to provide an improved understanding of the triggering mechanism of the 2014 landslide. Many authors have demonstrated the use of TLS for describing the topography and the structural setting of rock cliffs (Sturzenegger and Stead 2009 a, b;Fekete and Diederichs 2013;Francioni et al 2014). Distinct Element Methods have been widely used to simulate rock slope failure involving joint controlled displacements (Brideau and Stead 2010;Kalenchuk et al 2010;Sturzenegger 2011).…”

Section: Introductionmentioning

confidence: 99%

Back Analysis of the 2014 San Leo Landslide Using Combined Terrestrial Laser Scanning and 3D Distinct Element Modelling

et al. 2015

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Landslides of the lateral spreading type, involving brittle geological units overlying ductile terrains, are a common occurrence in the sandstone and limestone plateaux of the northern Apennines of Italy. The edges of these plateaux are often the location of rapid landslide phenomena, such as rock slides, rock falls and topples. In this paper we present a back-analysis of a recent landslide (February 2014), involving the north-eastern sector of the San Leo rock slab (northern Apennines, Emilia-Romagna Region) which is a representative example of this type of phenomena. The aquifer hosted in the fractured slab, due to its relatively higher secondary permeability in comparison to the lower clayey units leads to the development of perennial and ephemeral springs at the contact between the two units. The related piping erosion phenomena, together with slope processes in the clayshales have led to the progressive undermining of the slab, eventually predisposing large-scale landslides. Stability analyses were conducted coupling Terrestrial Laser Scanning (TLS) and Distinct Element Methods (DEMs). TLS point clouds were analyzed to determine the pre-and post-failure geometry, the extension of the detachment area and the joint network characteristics. The block dimensions in the landslide deposit were mapped and used to infer the spacing of the discontinuities for insertion into the numerical model. Threedimensional distinct element simulations were conducted, with and without undermining of the rock slab. The analyses allowed an assessment of the role of the undermining, together with the presence of an almost vertical joint set, striking sub-parallel to the cliff orientation, on the development of the slope instability processes. Based on the TLS and on the numerical simulation results, an interpretation of the landslide mechanism is proposed.

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“…Full automatic deformation monitoring technology based on LiDAR can monitor the structure in a non-contact way and is expected to be one of the most important directions in the field of SHM (structure health monitoring) in the future [1] [2][3] [4][5] [6]. LiDAR techniques can measure several million points in a short time with a high accuracy and has been used by many researchers for generating three-dimensional models in real-estate industry for visualization, in building renovation projects for surveying, and monitoring structure health [7] [17].…”

Section: Introductionmentioning

confidence: 99%

Automatic Processing Method for Deformation Monitoring of Circle Tunnels Based on 3D LiDAR Data

Xie¹,

Zhao²,

He³

et al. 2018

Preprint

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Abstract:The application of 3D LiDAR technology has become increasingly extensive in tunnel monitoring due to the large density and high accuracy of the acquired spatial data. The proposed processing method aims at circle tunnels and provides a clear workflow to automatically process raw point data and easily interpretable results to analyze tunnel health state. The proposed automatic processing method employs a series of algorithms to extract point cloud of a single tunnel segment without obvious noise from entire raw tunnel point cloud mainly by three steps: axis acquisition, segments extraction and denoising. Tunnel axis is extracted by fitting boundaries of the tunnel point cloud rejection in plane with RANSAC algorithm. With guidance of axis, the entire preprocessed tunnel point cloud is segmented by equal division to get a section of tunnel point cloud which corresponds to a single tunnel segment. Then the noise in every single point cloud segment is removed by clustering algorithm twice, based on distance and intensity. Finally, clean point clouds of tunnel segments are processed by effective deformation extraction processor to get ovality and three-dimensional deformation nephogram.

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Integration of three-dimensional laser scanning with discontinuum modelling for stability analysis of tunnels in blocky rockmasses

Cited by 105 publications

References 12 publications

Estimating in situ rock mass strength and elastic modulus of granite from the Soultz-sous-Forêts geothermal reservoir (France)

Estimating in situ rock mass strength and elastic modulus of granite from the Soultz-sous-Forêts geothermal reservoir (France)

Back Analysis of the 2014 San Leo Landslide Using Combined Terrestrial Laser Scanning and 3D Distinct Element Modelling

Automatic Processing Method for Deformation Monitoring of Circle Tunnels Based on 3D LiDAR Data

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