Documents published in Scipedia

• Peak Deviator Stress and Strain Uncertainty of Isotropically Consolidated Triaxial Compression Tests on Saturated Non-Cohesive Soils

  A. Miliopoulou*

  ISC2024.

  
  

  Abstract

  This paper presents the methodology for calculating the peak deviator stress and strain at peak deviator stress uncertainty of triaxial compression tests on water saturated, non-cohesive soils consolidated under isotropic conditions. A silicious sand sample is prepared in the same way to produce identical cylindrical specimens. These are then tested under the same conditions. Type A and type B uncertainty are calculated separately and used to yield the combined and expanded uncertainty of the main results, peak deviator stress and strain at peak deviator stress. For both measurands, type A uncertainty is significantly higher that type B and it is the factor mainly affecting the overall uncertainty of the results

  Abstract
  This paper presents the methodology for calculating the peak deviator stress and strain at peak deviator stress uncertainty of triaxial compression tests on water saturated, [...]

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• The Role and Performance of Instrumentation and Monitoring in Managing Risk During Deep Shaft Excavation in the Mercia Mudstone

  J. Birks*, I. Papadatos, M. Rufo

  ISC2024.

  
  

  Abstract

  The HS2 Bromford Tunnel intermediate shaft has an external diameter of 21.9m and a depth to formation of 47.1m below ground surface. The shaft is formed with a 63.1m deep 1.5m thick diaphragm wall primary lining, with a cast in situ secondary lining. The shaft works started in spring 2022, and formation level was reached in late 2023. Situated at the base of the Tame valley, the shaft excavation is predominately in the Mercia Mudstone, and is understood to be the largest and deepest excavation of its type in the Birmingham area. Instrumentation and monitoring played a vital role in managing ground risks during the diaphragm wall installation and bulk excavation. The paper covers: An overview of the shaft works and the subsequent tunnelling in the area; The geotechnical risks and parameters to be monitored; The specification, installation and performance aspects of the instrumentation, including the embedded SAAs and Vibrating Wire Piezometers; The design and performance of the specialists’ subcontractors dewatering system and excavation groundwater pressure behaviour during construction; Ground movements and third-party asset monitoring during diaphragm wall installation and excavation; diaphragm wall deflections during excavation - a comparison between design model calculations and actual monitored movement. As the shaft was constructed largely in advance of the main tunnelling works, some of the potential benefits from the experience and field observations made during the shaft works have been realised during the tunnelling.

  Abstract
  The HS2 Bromford Tunnel intermediate shaft has an external diameter of 21.9m and a depth to formation of 47.1m below ground surface. The shaft is formed with a 63.1m deep [...]

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• Dark Fibre Optic Cables for Shallow Ground Charactrization alongside Railroads

  E. Obando Hernandez, A. van Uitert*, P. Hölscher, P. Doornenbal, C. Mas, J. van ‘t Schip

  ISC2024.

  
  

  Abstract

  We evaluated the feasibility of existing fibre optic telecommunication cable as a Distributed Acoustic Sensors (DAS) for shallow ground characterization alongside railways and using the running trains as seismic source. We utilized 5 km of fibre optic cable alongside a railway segment localized in the Hanzelijn corridor in the Netherlands. For almost a week, we recorded strain generated by passing trains that was utilized to retrieve coherent and multimodal Rayleigh waves at various soil conditions. The data was recorded in a continuous mode, using a channel spacing of 1.0 m and a sampling frequency of 1,250 Hz. The DAS interrogator was set to a gauge length of 2.0 m to reach the highest possible spatial resolution. We captured at least 60 train passages (running alongside the fibre optic cable) per day. We extracted Rayleigh waves by utilizing seismic interferometry method. The seismic interferometry processing provided virtual broad-band shot-gathers with coherent and clear surface waves trends. The computed phase velocity spectrum at frequencies as high as 30 Hz and wavelength as short as 6 m. The retrieved dispersion curves allowed us to determine S-wave velocity profile at a minimum depth of exploration of 2.0 m. The measured Rayleigh waves and calculated S-wave velocities are comparable to reference values measured with standard Geophone and geotechnical data available at the test segment.

  Abstract
  We evaluated the feasibility of existing fibre optic telecommunication cable as a Distributed Acoustic Sensors (DAS) for shallow ground characterization alongside railways [...]

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• Monitoring of Tunnels in Urban Environments Complementing InSAR with in-situ Ground Instrumentation

  H. Cabrera, U. Lobón, S. Palanisamy*, A. Batalla, D. Albiol, M. Camafort, L. Bento, N. Devanthery

  ISC2024.

  
  

  Abstract

  One of the challenges in urban tunnelling projects is to guarantee that the infrastructure assets crossing or adjacent to the tunnel alignment and other new build elements are not affected by the construction activity. Radar Satellite Interferometry (InSAR) is a non-invasive surveying technique which provides millimetric deformation measurements of terrain structures over wide areas without any need to access site. This technique allows a comprehensive and periodic vision, with the same accuracy as manual levelling in cities for a fraction of the cost of traditional systems. ATLAS is the Sixense’s InSAR processing chain, aimed to monitor the different tunnelling activities phases: access shaft excavation, tunnel construction and settlement. This study focuses on real data obtained by Sixense during the monitoring of urban tunnel construction work in three major projects in London (UK) and Porto (Portugal), using a combination of technologies: InSAR for remote monitoring and two topographic instrumentation methods: Topographic Control Prisms through measurements with Robotic Total Station and Topographic Levelling. The methodology employed integrated InSAR to obtain surface deformation data across the tunnel influence zone and on-site instrumentation for detailed and precise measurements. Its implementation enabled continuous monitoring, revealing accurate and real-time deformation patterns near the tunnels. The results demonstrated a significant correlation between InSAR data and on-site measurements, validating the effectiveness of this combination.

  Abstract
  One of the challenges in urban tunnelling projects is to guarantee that the infrastructure assets crossing or adjacent to the tunnel alignment and other new build elements [...]

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• Delivery added value using field measurements through the application of the Observational Method

  H. Liew*, J. Marti, A. O'Brien

  ISC2024.

  
  

  Abstract

  High Speed Two (HS2) is the new high-speed railway line in the UK currently being constructed between London and Birmingham. The designs of many HS2 retaining structures, as can be the case for some projects in the UK, were progressed concurrently with ground investigation. In this situation, to manage uncertainties in the ground, a cautious assessment of ground parameters was usually adopted. The purpose of field monitoring varies depending on the responsible or interested party. For designers, the primary aim is usually for design verification of their permanent works design. This paper describes how field observations, particularly quality instrumentation and monitoring data, were used at HS2 Bromford Tunnel East Portal to improve the existing design as construction progressed to create savings. To improve the efficiency in data processing, DAARWIN, a machine learning-based technology was used. The design and construction of the eastern end of the Bromford Tunnel East Portal were modified by eliminating the requirements of temporary support using measured field data, site observations and a carefully controlled construction through the application of the Observational Method. The portal construction programme was shortened by at least two weeks despite only three of the remaining temporary steel props being omitted. The findings revealed opportunities to extend the application of the Observational Method on adjacent structures including Bromford Tunnel West Portal and Washwood Heath Retained Cut. Given the great length of retained excavations of the two structures, the potential efficiency gains in cost, time and carbon emissions are significant whilst enhancing safety.

  Abstract
  High Speed Two (HS2) is the new high-speed railway line in the UK currently being constructed between London and Birmingham. The designs of many HS2 retaining structures, [...]

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• Crossing a Landslide Area by a Motorway

  N. Pinyol*, G. Di Carluccio, J. Moya, J. Bertrand, E. Alonso

  ISC2024.

  
  

  Abstract

  A 1.5 km long stretch of a motorway built at midheigt of a valley eroded by an intermittent river, was almost completed in 2009. Budgetary restrictions led to a halt in construction. In the period 2009-2018, the motorway experienced severe damage, concentrated in three tributary shallow valleys, where the motorway was supported by compacted soil embankments. The “valleys” were, in fact, ancient landslides reactivated by the weight embankment of the embankment. The damaged embankments were substituted by bridges supported by pile foundations designed to resist the thrust of the active landslides. The bridges were completed by pile walls to improve the stability of the landslides. The construction of the wide roadway platform (40 m) required excavations at the mountainside, embankments at the riverside, additional stabilizing measures by anchored resisting walls, and systematic drainage. The miocene substratum is an irregular and heterogeneous set of conglomerate, sandstone, and claystone layers dipping 15-25º towards the river. The bedrock is covered by discontinuous quaternary clay and gravel formations. The paper describes: a) The singular sheared surfaces with very low friction, located in claystones, which were responsible for the instabilities observed; they played a key role in designing the stabilizing measures; b) The complex water pressure distribution and its variability in time, a consequence of the geological structure of substratum and the procedure designed to reduce pore water pressures and c) The difficulties encountered to install permanent high capacity anchors and the evolution of anchoring loads.

  Abstract
  A 1.5 km long stretch of a motorway built at midheigt of a valley eroded by an intermittent river, was almost completed in 2009. Budgetary restrictions led to a halt in construction. [...]

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• Preliminary tests on the UAV-enabled installation of wireless sensors for monitoring inaccessible slopes

  J. Gili*, M. Janeras, V. Salinas, O. Pedraza, A. Lluch, R. Carballo

  ISC2024.

  
  

  Abstract

  Although remote sensing techniques (TLS, DPS) are useful for monitoring wide areas with diffuse hazard, the deployment of sensors in contact with the ground (slopes, cliffs, rock blocks) is mandatory when a focused mechanism is underway. So far, most of the so-called ‘geotechnical sensors’ (tiltmeters, jointmeters, stress sensors), and some surveying systems or accessories (like prisms, targets, GNSS receivers), must be installed manually on the landslide body. Furthermore, in some cases cables for the power supply and data collection are needed. Besides the technical difficulties, in some scenarios this installation phase may imply a high risk for the operators. To overcome this issue, in the contribution we present some test carried out with wireless sensors installed by means of Uncrewed Aerial Vehicle (UAV). Concretely, we deployed several wireless precision tiltmeters, able to acquire several measures per minute, and with LOng-RAnge communication capability. The experiments were developed in the frame of a risk mitigation project leaded by the ICGC in the Montserrat massif (near Barcelona, Spain), an area of paramount geomechanical and societal interest. There, the targeted instability mechanisms are medium and large rockfalls. The preliminary tests show that the installation of sensors with UAV can be of great help in the aforementioned situations. The UAV-enabled deployment method should be considered to speed up the availability of real time monitoring data.

  Abstract
  Although remote sensing techniques (TLS, DPS) are useful for monitoring wide areas with diffuse hazard, the deployment of sensors in contact with the ground (slopes, cliffs, [...]

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• Using Combined Geotechnical and Geophysical Methods for Site Characterization of Ultra-Shallow Submerged Sites

  N. Stark*, M. Gardner, A. Lemnitzer

  ISC2024.

  
  

  Abstract

  Ultra-shallow underwater environments (average water depth ≲ 1 meters) in rivers, estuaries, and coastal zones represent the transition between water bodies and landmasses relevant for many engineering applications including utilities and transportation, habitat monitoring and restoration, and resilience to extreme flood and coastal storm events. With climatic shifts and an increased occurrence of extreme events, ultra-shallow underwater environments and inundation zones receive increasing attention. However, the increasing need for data revealed current limitations in safe accessibility and survey methodologies suitable for those conditions. Adaptation of geotechnical testing methods such as cone penetrometer testing and free fall penetrometer testing enable updated geotechnical testing capabilities, but these methods still require physical access to the measuring site which may be compromised by significant flow conditions, unknown debris and bottom conditions, limitations in access points and time, and combinations thereof. Remote sensing using optic sensors from unmanned aerial vehicles as well as from satellites offer strategies of soil classification in a rapid manner and without need for physical access if water conditions are clear. Advances in geoacoustic surveying, particularly regarding the use of sonars in ultra-shallow environments offers seabed surveying even in murky waters. Fusing geoacoustic and/or optic data with geotechnical point measurements enables the optimization of data collection in ultrashallow underwater environments or inundation zones in a safe and efficient manner, contributing also to available data from these environments to advance our understanding of soil mechanics in inundation zones and ultra-shallow waters. Here, an overview of available methods and recent advances in methodologies is presented supported by case studies including riverine and coastal environments.

  Abstract
  Ultra-shallow underwater environments (average water depth ≲ 1 meters) in rivers, estuaries, and coastal zones represent the transition between water bodies and landmasses [...]

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• Ambient Seismic Noise Imaging for Tailings Storage Facilities Monitoring: a Benchmark between Accelerometers and DAS

  L. Vivin*, C. Vulpe, L. McNab, A. Fourie, J. Boshoff, C. Cai, T. Allemand, T. Bardainne, J. Lepine, N. Lester

  ISC2024.

  
  

  Abstract

  Recent examples of tailings dam failure remind us how the monitoring of such sites is important. One major factor affecting the stability of tailings storage facilities (TSFs) is the presence and movement of water within the facility. Dam failures are often caused by seepage or the presence of weak layers within the tailings dam or the foundation soil. Thus, monitoring for the presence or movement of water within TSFs is becoming increasingly important, and solutions for permanent, non-intrusive and cost-effective monitoring of dams are a major challenge. One such solution is represented by geophysical imaging techniques such as ambient seismic noise interferometry. Through a research project, a nodal network system of accelerometer sensors was installed in a dense and random array on a TSF embankment wall at an Australian mine. Simultaneously, a fiber optic cable was deployed in a trench at the top of the TSF. Ambient seismic noise was recorded over a few weeks using the nodal network and with the fiber optic cable over several months using Distributed Acoustic Sensing (DAS) technology. Following data acquisition, benchmarking passive seismic imaging from the accelerometer network and the DAS system was conducted to evaluate the DAS capabilities for long-term TSF monitoring.

  Abstract
  Recent examples of tailings dam failure remind us how the monitoring of such sites is important. One major factor affecting the stability of tailings storage facilities (TSFs) [...]

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• Combining Remote Sensing Techniques to Optimize Digital Surface Models for Change Detection – A Case Study at a Pit Wall in the Canadian Cordillera

  T. Gierc*, R. Macciotta, F. Liu

  ISC2024.

  
  

  Abstract

  Slope monitoring is vital for open pit mines during operations and nearing closure where pit wall instabilities are present. Change detection using terrestrial laser scanning (TLS) has become part of the state of practice for collecting accurate measurements with extensive spatial coverage. The approach can detect displacements associated with global slope movement, as well as surficial occurrences such as rockfalls and sloughs. However, TLS acquisition quality is vulnerable to atmospheric interference and reflectivity of the target materials. In this regard, the high-density surface information obtained from TLS could be complemented with other, less detailed, remote sensing information in order to construct a complete surface model. Such an approach, however, requires a systematic workflow and a means to calculate surface model reliability. The subject of this study is an unstable pit wall at an open pit coal mine transitioning to closure. The site is located in the Canadian Cordillera, in a setting with intermittent fog and cloud cover, wildfire haze, and seepage within the slope face and toe. Insufficient TLS data can be obtained in local areas of the slope impacted by these conditions, as well as in shadowed areas on the benches above the TLS base elevation. Aerial photogrammetry was undertaken using UAV and combined with the TLS scan to generate a representative surface model. This paper presents a methodology for registration improvement between the TLS and UAV photogrammetry clouds, and evaluation of the combined surface using concepts of Limit of Detection (LOD) adopted from change detection techniques.

  Abstract
  Slope monitoring is vital for open pit mines during operations and nearing closure where pit wall instabilities are present. Change detection using terrestrial laser scanning [...]

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