Ageing of chalk rocks in underground quarry

Lafrance, Noémie; Souley, Mountaka; Auvray, Christophe; Favreau, Océane; Labiouse, V.

doi:10.1201/b16955-74

Cited by 3 publications

(4 citation statements)

References 2 publications

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“…In the SM underground quarry samples, no dissolution marks were observed at the edges of the pillar at the scale of our observations (Lafrance et al 2014), but dissolution marks become increasingly visible towards the centres of the pillars. In addition, a large decrease in the size of calcite crystals was observed from the edge to the centre of the pillar.…”

Section: Interpretation and Discussionmentioning

confidence: 85%

“…In the chalk from the EX underground quarry, the intensity of the traces of dissolution does not vary along the length of the core (Lafrance et al 2014), however the porosity accessible to water decreases from the pillar wall to the middle of the pillar. Water (vapour and/or liquid) will progressively dissolve crystals and penetrate a pillar towards its centre.…”

Section: Interpretation and Discussionmentioning

confidence: 99%

“…These fluctuations lead to chemical interactions between the chalk and the water, thereby affecting the mechanical behaviour of the chalk through changes in the weathering conditions (Talesnick et al 2001, Schroeder 2002, 2003, Risnes et al 2003, Duperret et al 2005, Nguyen 2010, Gombert et al 2013, Lafrance et al 2014. Preliminary laboratory characterization (e.g., mineralogical studies and uniaxial and triaxial compression tests) has also been undertaken (Gombert et al 2013, Lafrance et al 2014. Nevertheless, the hydro-chemo-mechanical behaviour of the chalk remains poorly understood due to complex interlocking phenomena that act on the mechanical behaviour of chalk.…”

Section: Description Of the Underground Quarriesmentioning

confidence: 99%

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Impact of weathering on macro-mechanical properties of chalks

Auvray

Lafrance

Souley³

et al. 2016

Rock Mechanics and Rock Engineering: From the Past to the Future

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Chalk has long been used as a strong building material. The shallow underground room-andpillar quarries where the chalk was extracted now lie abandoned and endure the effects of time and weathering, increasing their risk of collapse. The risk of instability is an issue for more than 10 000 towns in France. We have studied the physico-mechanical behaviour and ageing of two types of chalk in underground quarries in the Parisian Basin, France. The dolomitic chalk (Saint-Martin-Le-Noeud) exhibits variations in mechanical and physical properties with horizontal pillar depth, and both density and compressive strength appear to increase outwards from the core to the wall of the pillar. SEM analysis reveals progressive degradation and increasing homogeneity of the grains from the edge to the inside of the pillar. In contrast, in physico-mechanical tests and SEM analyses performed on the Estreux glauconitic chalk, no significant variation was observed between the pillar wall and pillar core.

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Section: Interpretation and Discussionmentioning

confidence: 85%

Section: Interpretation and Discussionmentioning

confidence: 99%

Section: Description Of the Underground Quarriesmentioning

confidence: 99%

See 1 more Smart Citation

Impact of weathering on macro-mechanical properties of chalks

Auvray

Lafrance

Souley³

et al. 2016

Rock Mechanics and Rock Engineering: From the Past to the Future

Self Cite

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show abstract

“…Tests of uniaxial and triaxial compression were also carried out on samples of this chalk brought to varying degrees of saturation, ranging from 90 to 98% following what can be found in situ in the mine (Lafrance et al 2014). This characterization with controlled humidity has established that the mechanical properties such as the deformability modulus (axial and lateral) and the uniaxial (Figure 5) and triaxial (Figure 6) compression resistance decrease when the relative humidity (or degree of saturation) increases.…”

Section: Physical Properties Of the Estreux Chalkmentioning

confidence: 99%

Geomechanical response of an abandoned chalk mine to multi-annual water table fluctuations

Gombert

Thoraval

Watelet

2018

Bull Eng Geol Environ

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The Paris basin contains 35,000 to 40,000 mines, most of which are abandoned, having mined chalk, a rock very sensitive to water. Although they have been excavated above the groundwater level, some of the mines can be temporarily or permanently flooded, due to (some) exceptional rainfall events. We have thus instrumented the chalk mine of Estreux (Nord department) to measure the impact of the oscillations of the water table on the stability of one of its pillars. It is a mine dug around 20 m deep by the chambers and pillars method. Now abandoned, it is temporarily flooded when the water table, located a few meters below the mine floor, rises due to heavy precipitation, which occurs on average every 8 years. From 2004 to 2012, a pillar was equipped with a convergence rod and two extensometers. There is a correlation between the vertical and horizontal deformation rates of the pillar and the periodic rise in the water table. Chalk samples were also taken in situ and their geomechanical properties characterized in the laboratory. On this basis, a first 3D mechanical simulation of the behavior of this pillar has been carried out taking into account elasticity, plasticity and creep. The calculated mean values of deformation generally match the measurements and the model succeeds in reproducing the annual fluctuations of these parameters in relation to those of the level of the water table. However, compared to the measurements carried out in situ, the current model exaggerates the vertical deformations compared to the horizontal deformations. However, with this first model we can observe that the variations in the water table induce elastic and reversible deformations of the pillar, given the absence of plastification of the chalk. These deformations are complementary to those due to the creep induced by the weight of the overlying grounds. If we want to model the long-term behavior of the pillar, particularly under the effect of the fluctuations of the water table induced by the climate change in progress, it is necessary to improve this model taking into account the hydromechanical couplings and the flows in unsaturated condition. In conclusion, it is proposed to use these data later in a complete mechanical model, still under development at INERIS.

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Influence of geology and topography on the occurrence of mine massive collapse—back-analysis of a historical collapse of chalk mine (France)

Heib¹,

Conil²,

Gombert

2023

Bull Eng Geol Environ

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Pillars of an underground mine are designed to ensure long-term stability and preserve the surface assets from the consequences of mining. However, long-term stability is never guaranteed. Over time, subsidence and collapses can occur, and the consequences are sometimes dramatic. Such collapses depend on the exploitation characteristics, the mechanical properties of the terrain, and the potential presence of water, but additional factors can play a major role. This study aims to identify the predisposing and triggering factors of the collapse, including stiff beds, cliffs, and faults. Back-analysis was carried out on a historic dramatic massive collapse of a chalk mine (Beaulieu, France, 1910). Numerical modeling (finite and distinct elements) was carried out to highlight the influence of mining geometry, the stiff bed, and the cliff. Then, the mechanism of the collapse of the Beaulieu mine was investigated. The results demonstrate the importance of the geometric configurations of the site for the development of such a phenomenon, particularly the cumulative effects of the excavation (extraction ratio), the cliff, and the stiff bed. These cumulative factors increase the risk of a massive collapse. This study has shown that the stability of abandoned room and pillar underground mines should cover three concepts: estimation of the stress state of the pillars, the strength of the pillars, and the presence of a cliff as well as a significant discontinuity crossing the rock mass which could be a fault.

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Ageing of chalk rocks in underground quarry

Cited by 3 publications

References 2 publications

Impact of weathering on macro-mechanical properties of chalks

Impact of weathering on macro-mechanical properties of chalks

Geomechanical response of an abandoned chalk mine to multi-annual water table fluctuations

Influence of geology and topography on the occurrence of mine massive collapse—back-analysis of a historical collapse of chalk mine (France)

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