Chapter 6: Bearing Capacity of Foundations. Chapter 7: Settlement of Foundations. Chapter 8: Consolidation. Chapter 9: Foundations on Expansive Soil. Chapter Slope Stability. Chapter Retaining Walls. Chapter Foundation Deterioration and Cracking. Chapter Geotechnical Earthquake Engineering for Soils. Part 3: Foundation Construction.
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Part 4: International Building Code. Part 5: Appendices. Chapter Geotechnical Earthquake Engineering for Soils For geotechnical earthquake engineering of soils and foundations, the types of activities that may need to be performed by the geotechnical engineer include the following: Subsurface exploration for geotechnical earthquake engineering, i. Featured Products. View All Featured Products. Remote sensing, via spaceborne or airborne sensors, are other tools that have emerged as a crucial component of documenting the effects of natural disasters Rathje and Franke, Commercial optical satellites routinely obtain sub-meter imagery that can be used to assess the geographical distribution of damage.
Satellite imagery is geo-referenced to standard cartographic projections, and thus observations from the imagery can be fused with ancillary information such as geologic maps, topographic maps, or any other information that has been geo-referenced. Satellite imagery was used to document the distribution of landslides from the Niigata-ken Chuetsu earthquake Rathje et al.
Another example is the integrated documentation of geotechnical damage along the primary north-south highway in Chile Ruta 5 following the Chile earthquake by Frost and Turel Unmanned aerial vehicles UAVs are aerial robots that can be remotely controlled and can carry a wide variety of sensors.
This technology is becoming more common as a platform for remote sensing in the aftermath of catastrophic events. The most common sensor deployed on a UAV is a digital camera. The images collected by a UAV can be used to visually examine earthquake effects over a large site from a broader perspective, but they can also be used to develop 3D point clouds of a site. Notwithstanding the important emerging role of new hardware and software technologies as noted above, long-established and widely used traditional methods of data collection and information sources remain a critical component of GEER reconnaissance activities.
Detailed mapping is possible with differential GPS devices, such as total stations. The importance of detailed mapping and surveying of damaged areas relative to general damage surveys cannot be overemphasized, as they provide the data for ground-referencing well-documented case histories that drive the development of many of the empirical design procedures used in earthquake engineering practice.
Geotechnical Earthquake Engineering
Geologic maps, topographic maps, soil reports, and damage reports can be collected from various sources to help complete the picture of what happened and prepare for subsequent support studies that allow the profession to discern why it happened. Field observations, detailed mapping and measurements, and remote sensing technologies provide diverse data at different spatial and temporal scales. Together they offer opportunities to develop more comprehensive observations of damage.
Additionally, the fusion of observations from different sources can lead to more comprehensive assessments of failure mechanisms. The data can also be integrated with other types of geospatial information, such as geologic maps, topographic maps, and Shakemaps of ground motion, to explore the relationships between damage and potentially important factors. This integration is facilitated by the fact that all damage observations can be geo-referenced to standard cartographic projections using GPS.
Data fusion can be facilitated through open-access data repositories, such as the Data Depot data repository and Reconnaissance Portal available at the DesignSafe cyberinfrastructure for natural hazards engineering, and cloud-based data analysis tools that can access various datasets where they reside on the cloud. Against the backdrop of the event responses summarized above, GEER has a history of important contributions and accomplishments across a variety of activities.
A selection of these earthquake-focused responses are noted below. In all cases, GEER team members collaborated with various local, state, and federal agencies. A brief synopsis of some of these responses over the past 5 years is provided below to illustrate the range of activities:. The preliminary objective of the reconnaissance was to record the effects of strong shaking and ground failure on infrastructure, including the presence of liquefaction, landslides, and surface fault rupture.
Within 24 h of the event, initial observations showed a remarkable absence of liquefaction or landslide induced ground deformations. However, there was well-defined surface rupture that produced various types of damage to structures and there was a pattern of damage to sidewalks and curbs suggesting sympathetic ground deformations within the vicinity of the fault zone.
The earthquake sequence resulted in nearly 9, deaths, tens of thousands of injuries, and left hundreds of thousands of inhabitants homeless. With economic losses estimated at several billion US dollars, the financial impact to Nepal was severe and the rebuilding phase will likely span many years.
The overall distribution of damage relative to the epicenter indicates significant ground motion directivity, with pronounced damage to the east and comparatively little damage to the west. Although modern buildings constructed within the basin generally performed well, local occurrences of heavy damage and collapse of reinforced concrete structures were observed.
Ground failures in the basin included cyclic failure of silty clay, lateral spreading, and liquefaction. Innovative reconnaissance approaches combined satellite imagery, local imagery from LIDAR and UAV-based photographs, and traditional field mapping was undertaken of structural damage patterns, landslides, surface fault rupture, and other effects.
Observations made during the GEER reconnaissance activities are having an impact in research on fragility of masonry structures, ground motions from normal fault earthquakes, landslides in complex geologic terrain, and surface fault rupture. Observed foundation performance in areas of structural damage varied considerably. Despite the high plasticity lacustrine clays that are predominant in Mexico City, numerous cases of seismic-induced settlements ranging from 1 to 15 cm were observed in the free-field soils around end-bearing pile-supported structures.
Several cases of tilted structures 1—3 degrees were observed. These structures generally were supported on a combined friction pile and mat slab foundation system. A common characteristic and lesson of the above listed responses, and indeed all GEER responses, is the reinforcement of the need for timely well-coordinated responses that allow for critical perishable data to be gathered. Apart from the inherent value of the data itself, it also provides critical insight into responses that need additional study and investigation, either through physical experimentation or numerical simulations.
Further, the beneficial role of emerging advanced technology-based data collection continues to increase. Through the capabilities and creativity of its team members, GEER is recognized as an early adopter of advanced data collection technologies. From the adoption of handheld GPS systems in in Turkey, to dedicated mobile computing software data collection solutions in in India, to satellite and Terrestrial LIDAR Scanning based assessments of landslide distributions in Japan in , to use of GoogleEarth TM photo logs in in Japan, to use of social media data to assess damage in in Colorado, to use of UAV platforms in in Chile, GEER teams have led the natural hazards reconnaissance community in adopting and deploying new advanced technologies.
Apart from the inherent benefits associated with using these technologies in terms of data quality and quantity, they yield significant efficiencies in team performance and facilitate deployment of GEER resources in locations likely to yield the most impactful perishable data. Summaries of the specific use of these technologies following recent earthquakes are provided below. Left-lateral strike-slip fault rupture with minor reverse fault movement occurred on a previously unmapped fault and produced strong ground shaking and subsequent structural damage to the Tainan area.
The ground shaking was accompanied by landsliding, liquefaction, and lateral spreading, and most liquefaction was confined to spots containing low-quality backfill soil Sun et al.
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A GEER reconnaissance team deployed rapidly after local emergency response efforts concluded, and they spent 1 week observing and collecting perishable data. Reconnaissance efforts focused on the geologic influence on ground motions, liquefaction of sandy soils, performance of buildings and foundations atop liquefiable soil, and performance of non-symmetrical and soft-story buildings.
The GEER team observed that buildings with continuous, well-connected foundations or sitting atop basements performed well in areas where liquefaction occurred, whereas those without well-connected foundations incurred heavy damage Sun et al. Aerial imagery via a quadcopter UAV also provided photogrammetry datasets with which to create 3D point cloud models using SfM.
The point cloud data did not require control points on the ground; instead, the UAV photos for this reconnaissance were geo-tagged so that the relative locations of the viewpoints of each image could be used directly to create high-resolution, 3D models such as that shown in Figure 5. Figure 5. The central Italy earthquake sequence began with a M w 6.
This event caused significant damage, mostly to unreinforced masonry homes, in the villages of Arquata del Tronto, Accumoli, Amatrice, and Pescara del Tronto, causing fatalities Zimmaro and Stewart, Evacuation orders were put in effect before two more large earthquakes of M w 5. The reconnaissance team utilized a variety of UAVs equipped with high-resolution cameras to obtain photogrammetric imagery with which to develop 3D models of damage sites using SfM. While the quadcopter and helicopter UAVs needed to be manually controlled, the fixed-wing UAV was programmed to follow a specific flight path using selected waypoints.
Figure 6. Orthophoto of the town of Accumoli developed with images obtained via fixed-wing UAV SfM proved to be especially useful in obtaining 3D imagery for significant landslide events occurring in rugged or steep terrain, in heavily vegetated areas, or in other areas with limited site access. For example, Figure 7 shows a 3D image of a slope failure in Pescara del Tronto resulting from retaining wall failure. The SfM imagery and point cloud data can be used to perform further quantitative analyses post-reconnaissance, and this data can be further verified for accuracy by combining them with other geomatics technologies such as LIDAR.
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The M w 7. The rupture progressed north-eastward, producing surface fault rupture, strong ground shaking, landslides, liquefaction, and lateral spreading in the South Island of New Zealand and in the capitol city of Wellington Cubrinovski and Bray, Key observations and preliminary findings are presented in papers such as Cubrinovski et al.
A unique feature of the response to this earthquake was the development of a detailed landslide inventory within 8 days of the event, and this inventory was used to guide the GNS-UC-GEER reconnaissance efforts. The detailed landslide inventory utilized both moderate resolution 15 m Landsat 8 imagery and high resolution 1. The Landsat 8 imagery covered an area of about 1, km 2 and was used initially because it was available within 24 h of the event.
The high-resolution imagery became available starting about 2 days after the event and the final set of 65 images covered a broader area of about 7, km 2. Visual identification was used to identify the landslides, and this approach relies on the ability to see the landslides in the imagery.
The simplest approach is to display the imagery as natural color, the color observed with the naked eye, and landslides are generally identified as locations where the vegetation is stripped away, exposing the underlying soil and rock material. The sharp contrast in color is easily distinguished when the proper color bands are selected and cloud cover is minimal to non-existent.
To ensure that an area of stripped vegetation does not represent a landslide existing before the earthquake, pre-event imagery can be checked manually Figure 8.
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Each landslide was identified as a polygon, and no attempt was made to differentiate the source area from the landslide debris. The total number of landslides in the final inventory was 1, The digital landslide inventory was brought to the field to guide reconnaissance efforts and was ground-truthed in real-time during a helicopter reconnaissance over the affected area.
Figure 8. Pre-event Google Earth imagery and post-event Worldview-2 imagery of Leder River landslide from the Kaikoura earthquake The floor slab of this building was not pile-supported and settled up to mm relative to adjacent pile-supported structures. Figure 9. Figure 10A shows measurements of liquefaction-induced settlement across CentrePort along the cross-section line shown in Figure 10C. The deck of King's Wharf, supported on driven timber piles as shown in Figure 10B , underwent lateral displacement due to lateral spreading in the fill behind it, which tilted and split the supporting timber piles.
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Figure 10D shows the manifestation on the Thorndon Wharf deck of differential settlement between the ground and a buried precast concrete seawall. The LIDAR scans provided point cloud data with which to measure small displacements on the order of centimeters due to liquefaction and lateral spreading, and they supplement SfM models gained via UAV photogrammetry. Figure Normal fault rupture occurred at a focal depth of 57 km in an instraslab subduction zone 60 km southwest of Puebla and km southeast of Mexico City.
Ground motion records indicated a higher frequency content in the soft clay underlying Mexico City than observed during the Michoacan earthquake.
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They used ground-based LIDAR to model the interior and exterior of damaged structures and facilities. A 40 m wide landslide occurred adjacent to this bridge, damaging the roadway approach to the bridge and its southwest wing wall. The team gathered UAV imagery of this bridge and stitched the imagery together using SfM technology to create a 3D model of the damaged bridge as shown in Figure The figure shows the landslide-related damage to the bridge as well as the 40 m width of the landslide and tension cracks forming up the slope behind the slide.
In total, the GEER main team and advance team conducted UAV surveys at 23 different locations and LIDAR surveys at 5 locations, garnering over GB of image data that allow researchers to continue to analyze damages even after the conclusion of field reconnaissance Mayoral et al. The collection of perishable data in the immediate aftermath of events has enabled GEER team members and others to make important contributions to the advancement of hazards research.
Selected examples include:. That data, in turn, spawned a large-scale research program sponsored by the California Department of Water Resources DWR to develop fragility models for flood control levee segments. Those fragility models, which are directly usable under certain conditions and more generally for validation of numerical models, are being used by DWR and others e.
Such assessments are crucial for water agencies and the communities they serve e. Further, adjacent structures were observed to affect each other's performance due to dynamic coupling and excessive residual tilt. These events revealed the need for liquefaction remediation to achieve satisfactory performance at a scale beyond that of an isolated building and has stimulated research in this area. Examples are the refinement of the Boulanger and Idriss CPT-based liquefaction triggering procedure, which used New Zealand data to improve its MSF and FC adjustments, and the development of the Bray and Macedo simplified liquefaction-induced building settlement procedure, which used the building settlement and performance data to calibrate their numerical simulation and to validate the simplified procedure.
No damage was observed in these HDPE pipelines after the Christchurch, 13 June, and 23 December earthquakes, even though this area was subjected to severe liquefaction, with settlement and lateral spreading as high as 3 m. This deployment of HDPE ductile pipelines represents the first documented case where HDPE pipelines installed for earthquake resistance have been subjected to large liquefaction-induced ground displacements.
These developments are extraordinarily important for lifeline earthquake-resistant design and construction. Over the past two decades, GEER has made significant advances in achieving its objectives. To achieve these dual objectives, GEER has identified a set of tasks that build on past successes and accomplishments yet seek to advance the science and engineering of post-disaster reconnaissance.
GEER will continue to coordinate the response of the geotechnical hazards community to future events. Similarly, protocols for utilizing the NHERI DesignSafe cyberinfrastructure during field reconnaissance activities as well as for archiving and disseminating data collected during GEER responses will be developed.
Similar collaborations are anticipated with other disciplinary platforms when they are established. Early adoption of advanced technologies for post-disaster reconnaissance will continue to be a cornerstone of GEER activities in the future. At the same time, GEER actively seeks out researchers and practitioners with new technologies that can enhance the quality and quantity of data collected. As has been a requirement for all GEER reconnaissance activities since , all data has to be geo-referenced.
Not only does this allow for rapid integration of data from multiple different sources but it facilitates the sharing with and utilization by others of data collected by GEER teams. GEER will enhance its utilization of social media data as part of future reconnaissance efforts. Another focus area for GEER will be to better use data mining techniques during both the preparation for response activities as well as in preparing post-event reports.
With the ever-increasing amount of digital data archived and readily available, GEER can enhance both the manner in which it plans reconnaissance activities as well as documents team findings. This can also be facilitated by expanded use of GEER teams to include a number of individuals who are data experts but do not necessarily travel to the field. One of the primary objectives of GEER reconnaissance activities is to acquire the perishable data upon which well-documented case histories can be developed through follow-on field, laboratory, and numerical studies.
Historically, many of these case histories have been event-driven. For example, only by observing the performance of systems and infrastructure in actual events do deficiencies in understanding become evident and lead to further studies. In short, many of the case histories might be described as reactionary to event observations.
With the significant large-scale experimental and simulation capabilities now available through the NSF NHERI and similar infrastructure, there is also an opportunity to identify potential behaviors and phenomena during these experiments that can help guide future reconnaissance activities and thus research topics.
In other words, there is now an opportunity to identify, ahead of an event, possible effects of interest to allow for enhanced calibration and validation of experimental and numerical simulations. The establishment and existence of the DesignSafe cyberinfrastructure as part of the NHERI has opened up significant opportunities for streamlining the flow of data from initial collection in the field to access by other researchers, and subsequent analysis and integration of data using the tools available in the DesignSafe Data Depot and Discovery Workspace.
As GEER moves to the next phase of its existence and operation, focused effort will be devoted to leveraging this cyberinfrastructure. As more data intensive and computation intensive techniques are used to collect field observations of earthquake effects, the challenge becomes how best to archive these datasets for long term use and re-use. This is particularly the case for high resolution point clouds from LIDAR and SfM, although all reconnaissance efforts would benefit from more formal and organized publishing of field data.
The DesignSafe cyberinfrastructure web platform provides a data repository and data analysis tools that can be used to share and publish reconnaissance data Rathje et al. Knowledge can be advanced through the careful documentation of the effects of important earthquakes.
Recent GEER studies and associated reports illustrate what effective post-earthquake geotechnical reconnaissance can accomplish. GEER reconnaissance efforts have succeeded in large part because of the value that geotechnical engineers place on learning from earthquakes and on developing well-documented case histories that form the cornerstone of understanding for the geotechnical engineering profession.
The death and destruction resulting from recent events emphasize society's need to improve its resilience. It is critical that the geotechnical engineering profession continues to capture the perishable data that enables it to understand which design procedures result in good performance and which procedures need improvement. With robust field data and observations and the resulting insights and knowledge, geotechnical engineering researchers can advance key concepts in performance-based earthquake engineering. In this context, GEER helps turn disaster into knowledge to enhance resilience.
All authors listed have made a substantial, direct and intellectual contribution to the work, and approved it for publication. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the NSF. Richard Fragaszy and the late Dr.
Cliff Astill. GEER members also donate their time, talent, and resources to collect time-sensitive field observations of the geotechnical effects of extreme events.
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