The Influence of Pre-Existing Tension Cracks on the Stability of Unsupported Temporary Excavations in Stratified Hard Clays: Case Study of Corfu Island, Northwestern Greece
Slope failures in overconsolidated hard clays present significant geotechnical challenges, particularly in stratified formations prone to pre-existing discontinuities. Despite extensive research on residual shear strength and fissuring in stiff clays, the role of undetected tension cracks and their...
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2025-05-01
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| author | Panagiotis Pelekis Anastasios Batilas Spyridon Lainas Nikolaos Depountis |
| author_facet | Panagiotis Pelekis Anastasios Batilas Spyridon Lainas Nikolaos Depountis |
| author_sort | Panagiotis Pelekis |
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| description | Slope failures in overconsolidated hard clays present significant geotechnical challenges, particularly in stratified formations prone to pre-existing discontinuities. Despite extensive research on residual shear strength and fissuring in stiff clays, the role of undetected tension cracks and their interaction with hydrogeological conditions in temporary excavations remains underexplored. This study addresses this research gap through a detailed case study of a slope failure during an unsupported residential excavation on Corfu Island, Greece. The investigation aimed to identify the failure mechanism, assess the influence of geological discontinuities and groundwater conditions, and evaluate the contribution of residual shear strength to slope stability. The methodology combined field observations, laboratory testing (including unconfined compression and ring shear tests), and numerical modelling using both finite element (FEM) and limit equilibrium (LEM) approaches. The results revealed that a nearly vertical, pre-existing fissure—acting as a tension crack—and water infiltration along the clay–sandstone interface significantly reduced the factor of safety, triggering a planar slide. Both FEM and LEM analyses indicated that critical conditions for failure were reached with a residual friction angle of 19°, inclined sandstone layers at 15–17°, and hydrostatic pressure from groundwater accumulation. This study demonstrates the compounded destabilizing effects of undetected discontinuities and water pressures in stratified hard clays and underscores the necessity of comprehensive geotechnical assessments for temporary excavations, even in seemingly stable formations. |
| format | Article |
| id | doaj-art-32db5ee5acf4432bb9d592d2fa63e057 |
| institution | Kabale University |
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| language | English |
| publishDate | 2025-05-01 |
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| series | Geosciences |
| spelling | doaj-art-32db5ee5acf4432bb9d592d2fa63e0572025-08-20T03:48:01ZengMDPI AGGeosciences2076-32632025-05-0115518710.3390/geosciences15050187The Influence of Pre-Existing Tension Cracks on the Stability of Unsupported Temporary Excavations in Stratified Hard Clays: Case Study of Corfu Island, Northwestern GreecePanagiotis Pelekis0Anastasios Batilas1Spyridon Lainas2Nikolaos Depountis3Department of Civil Engineering, University of Patras, 26504 Patra, GreeceVenterra Group, Gavin & Doherty Geosolutions Ltd., D14 X627 Dublin, IrelandDepartment of Geology, University of Patras, 26504 Patra, GreeceDepartment of Geology, University of Patras, 26504 Patra, GreeceSlope failures in overconsolidated hard clays present significant geotechnical challenges, particularly in stratified formations prone to pre-existing discontinuities. Despite extensive research on residual shear strength and fissuring in stiff clays, the role of undetected tension cracks and their interaction with hydrogeological conditions in temporary excavations remains underexplored. This study addresses this research gap through a detailed case study of a slope failure during an unsupported residential excavation on Corfu Island, Greece. The investigation aimed to identify the failure mechanism, assess the influence of geological discontinuities and groundwater conditions, and evaluate the contribution of residual shear strength to slope stability. The methodology combined field observations, laboratory testing (including unconfined compression and ring shear tests), and numerical modelling using both finite element (FEM) and limit equilibrium (LEM) approaches. The results revealed that a nearly vertical, pre-existing fissure—acting as a tension crack—and water infiltration along the clay–sandstone interface significantly reduced the factor of safety, triggering a planar slide. Both FEM and LEM analyses indicated that critical conditions for failure were reached with a residual friction angle of 19°, inclined sandstone layers at 15–17°, and hydrostatic pressure from groundwater accumulation. This study demonstrates the compounded destabilizing effects of undetected discontinuities and water pressures in stratified hard clays and underscores the necessity of comprehensive geotechnical assessments for temporary excavations, even in seemingly stable formations.https://www.mdpi.com/2076-3263/15/5/187temporary excavationsstratified hard claystension cracksresidual shear strengthgeological engineeringGreece |
| spellingShingle | Panagiotis Pelekis Anastasios Batilas Spyridon Lainas Nikolaos Depountis The Influence of Pre-Existing Tension Cracks on the Stability of Unsupported Temporary Excavations in Stratified Hard Clays: Case Study of Corfu Island, Northwestern Greece Geosciences temporary excavations stratified hard clays tension cracks residual shear strength geological engineering Greece |
| title | The Influence of Pre-Existing Tension Cracks on the Stability of Unsupported Temporary Excavations in Stratified Hard Clays: Case Study of Corfu Island, Northwestern Greece |
| title_full | The Influence of Pre-Existing Tension Cracks on the Stability of Unsupported Temporary Excavations in Stratified Hard Clays: Case Study of Corfu Island, Northwestern Greece |
| title_fullStr | The Influence of Pre-Existing Tension Cracks on the Stability of Unsupported Temporary Excavations in Stratified Hard Clays: Case Study of Corfu Island, Northwestern Greece |
| title_full_unstemmed | The Influence of Pre-Existing Tension Cracks on the Stability of Unsupported Temporary Excavations in Stratified Hard Clays: Case Study of Corfu Island, Northwestern Greece |
| title_short | The Influence of Pre-Existing Tension Cracks on the Stability of Unsupported Temporary Excavations in Stratified Hard Clays: Case Study of Corfu Island, Northwestern Greece |
| title_sort | influence of pre existing tension cracks on the stability of unsupported temporary excavations in stratified hard clays case study of corfu island northwestern greece |
| topic | temporary excavations stratified hard clays tension cracks residual shear strength geological engineering Greece |
| url | https://www.mdpi.com/2076-3263/15/5/187 |
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