Evolution of shear bands and cracks in multi-stage triaxial tests with water-saturated sandstone: A study of micro-tectonics with a fractal perspective

Lempp, Christof; Menezes, Flora Feitosa; Schöner, Angelika

doi:10.1016/j.jsg.2020.104092

Cited by 8 publications

(9 citation statements)

References 13 publications

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“…4 that this argument is contestable and not supported by triaxial 'jacketed' and 'unjacketed' tests. Multi-stage triaxial tests with water-saturated sandstone [16] prove the validity of (1) with overall stresses, which can again be attributed to the p w -neutrality of minerals. This is a perspective for critical phenomena of geomatter with pore water from geotechnical operations to bigger parts of the lithosphere (Sect.…”

Section: Introductionmentioning

confidence: 64%

“…0 orr 0 1 ! 0 led to axial splitting or horizontal discing, respectively, whereas with a [16]). Deviators of overall stress versus spatial mean overall pressure minus pore pressure at one endplate sufficientp 0 1 3 ðr 0 1 þ 2r 0 3 Þ, shear band patterns arose without cracks.…”

Section: Water-saturated Porous Rockmentioning

confidence: 97%

“…The findings of Lempp et al [16] deepen the understanding of tectonic critical phenomena beyond Sornette 22, but rise several questions. A Mohr-Coulomb condition with overall stresses helps explain tectonically active parts of the lithosphere with the World Stress Map, but therein, stresses depend on the mesh size [11], which speaks for fractal spatial distributions so that the size of volume elements with the same centre influences overall stresses.…”

Section: Water-saturated Porous Rockmentioning

confidence: 99%

“…All these mean-field approaches assume an amorphous fabric so that cracks and shear bands are excluded, while Lempp et al [16] focus on structural changes of the solid fabric in multi-stage triaxial tests with water-saturated sandstone. Initially, intact samples were repeatedly brought to limit states by increasing the overall amount of stress deviator jr 1 Àr 3 j and/or pore water pressurep w , avoiding disintegration by means of a servo-control.…”

Section: Water-saturated Porous Rockmentioning

confidence: 99%

“…Unrolled combined photographs of a sandstone sample after a multi-stage triaxial test[16] Limit stress states of water-saturated sandstone samples, attained in multi-stage triaxial tests (modified from Lempp et al…”

mentioning

confidence: 99%

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Implications of the principle of effective stress

Gudehus

2020

Acta Geotech.

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While Terzaghi justified his principle of effective stress for water-saturated soil empirically, it can be derived by means of the neutrality of the mineral with respect to changes of the pore water pressure $$p_w$$ p w . This principle works also with dilating shear bands arising beyond critical points of saturated grain fabrics, and with patterns of shear bands as relics of critical phenomena. The shear strength of over-consolidated clay is explained without effective cohesion, which results also from swelling up to decay, while rapid shearing of water-saturated clay can lead to a cavitation of pore water. The $$p_w$$ p w -neutrality is also confirmed by triaxial tests with sandstone samples, while Biot’s relation with a reduction factor for $$p_w$$ p w is contestable. An effective stress tensor is heuristically legitimate also for soil and rock with relics of critical phenomena, particularly for critical points with a Mohr–Coulomb condition. Therein, the $$p_w$$ p w -neutrality of the solid mineral determines the interaction of solid fabric and pore water, but numerical models are questionable due to fractal features.

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Section: Introductionmentioning

confidence: 64%

Section: Water-saturated Porous Rockmentioning

confidence: 97%

Section: Water-saturated Porous Rockmentioning

confidence: 99%

Section: Water-saturated Porous Rockmentioning

confidence: 99%

mentioning

confidence: 99%

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Implications of the principle of effective stress

Gudehus

2020

Acta Geotech.

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Investigating the Time-Dependent Behavior of Intact Rocks and Fractured Rocks Using Unconfined Relaxation Testing in Underground Coal Mines

Khoshmagham,

Hosseini Alaee,

Shirinabadi

et al. 2024

Geotech Geol Eng

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Depletion-induced seismicity in NW-Germany: lessons from comprehensive investigations

Gudehus

Lempp²,

Scheffzük

et al. 2022

Acta Geotech.

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Evaluating various investigations for north-German gas fields, we discuss past and actual evolutions of the rock fabric in the light of dilatant driven and spontaneous contractant critical phenomena. Features of the latter were discovered by multi-stage triaxial tests with water-saturated sandstone samples and were similarly observed around the gas fields. A Mohr–Coulomb condition with quasi-local stress components ($${\hat{\sigma }}'_1$$ σ ^ 1 ′ and $${\hat{\sigma }}'_3$$ σ ^ 3 ′ ), and variable parameters $$\phi $$ ϕ ’ and $${{\hat{c}}}'$$ c ^ ′ , can capture successive critical states of the solid fabric. The implied driven dilatation up to a collapse with contraction is captured by a stress-dilatancy relation. Fractal patterns of shear bands (faults) dominate if the smallest principal stress $${\hat{\sigma }}'_3$$ σ ^ 3 ′ exceeds $${{\hat{c}}}'$$ c ^ ′ , otherwise cracks dominate and can lead to a rockburst. Triaxial tests with X-ray attenuation, seismometry including the splitting of shear waves and/or neutron beam diffraction contribute to clarification and validation. Seismic early warning and calculation models for various geotechnical operations with dominating faults can thus be improved, but the task is more difficult for rockbursts.

show abstract

Evolution of shear bands and cracks in multi-stage triaxial tests with water-saturated sandstone: A study of micro-tectonics with a fractal perspective

Cited by 8 publications

References 13 publications

Implications of the principle of effective stress

Implications of the principle of effective stress

Investigating the Time-Dependent Behavior of Intact Rocks and Fractured Rocks Using Unconfined Relaxation Testing in Underground Coal Mines

Depletion-induced seismicity in NW-Germany: lessons from comprehensive investigations

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