Documents published in Scipedia

• 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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• Piezometers: a very important instrument to which we need to pay more attention

  J. Raventos*

  ISC2024.

  
  

  Abstract

  Piezometers are instruments that can produce high-quality information if suitable and effective installation and monitoring procedures are followed. In order to minimise errors and optimise quality of the obtained information, we must pay attention when prescribing the type of piezometer and its installation, as highlighted in the ISO/EN18674 standards. The use of piezometers as a geotechnical instrument is a commodity. This paper aims to exemplify how the use of piezometers can be optimised and how the most common errors can be avoided.

  Abstract
  Piezometers are instruments that can produce high-quality information if suitable and effective installation and monitoring procedures are followed. In order to minimise errors [...]

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• Revealing Structures below Vegetation using UAV-BASED LIDAR

  M. Horn*, M. Seitz

  ISC2024.

  
  

  Abstract

  LiDAR has been used for the last decade to create digital terrain models using Airborne Laser Scans (ALS) with about 10 points per square metre, mainly depending on flight altitude and speed. The data is used to produce elevation maps or digital surface models, calculate volumes and analyse the Earth's surface or objects above it. However, the resolution and elevation accuracy of about ± 0.3 m means that calculations are only estimates and ground features may not be identified. Unmanned aerial vehicle based LiDAR systems have some advantages over ALS data. Their lower altitude and speed allow the scanner to generate more points per square metre than an ALS. The more laser beams the scanner emits into the same area, the more beams pass through the vegetation and generate more points on the ground or other objects. This increases the level of detail in the digital terrain model. Reference points are another way of increasing the accuracy of the LiDAR scan. These points are placed within the survey area and have known coordinates and elevations to control and fit the result of the LiDAR scan to the coordinate system of the reference points. This data can be used for higher accuracy volume calculations and changes in the terrain structure (e.g. geological changes). Because the terrain is mapped at a high level of detail, it can also be used in explosive ordnance disposal to reveal hidden features such as trenches or bomb craters that may cause a problem for the project.

  Abstract
  LiDAR has been used for the last decade to create digital terrain models using Airborne Laser Scans (ALS) with about 10 points per square metre, mainly depending on flight [...]

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• Event detection system for monitoring the cliff retreat and undermining of Castellfollit de la Roca village

  M. Navarro*, M. Janeras, T. Carbonell, J. Pérez

  ISC2024.

  
  

  Abstract

  Castellfollit de la Roca village (Catalonia, NE of Spain) stands on top of a basaltic cliff affected by rockfalls that are causing the retreat of the slope and the risk of undermining the buildings. So far, remote sensing techniques have been applied. They have detected centimetric precursory movements of toppling in basaltic columns, and unnoticed rockfalls of tiny volume as well. However, rockfalls of remarkable magnitude caused by other mechanisms have occurred at the foundation level of some houses, without any precursor movement detected by remote sensing techniques. In order to gather information from these events, a priority sector has been instrumented with a geotechnical network of crackmeters, tiltmeters and thermistors to monitor the thermo-mechanical behavior of the rock mass. Readings from the sensors have been automated through a wireless network based on Loadsensing nodes and gateway connected by LoRa technology. Tiltmeters are all-in-one devices of sensor and logger operating in dynamic mode. This system enables the detection of events and sending alert messages in real time. To receive reliable alerts for risk management, suitable thresholds have to be defined, based on the knowledge of the studied phenomena at the particular scenario. This paper presents the system set up and the threshold analysis through the observation of the cliff behavior on the daily and seasonal cycles registered during the first year of operation.

  Abstract
  Castellfollit de la Roca village (Catalonia, NE of Spain) stands on top of a basaltic cliff affected by rockfalls that are causing the retreat of the slope and the risk of [...]

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