acase@tulane.edu / Land-surface subsidence can be a major contributor to the relative sea-level rise that is threatening many coastal communities. Loosely constrained subsidence rate estimates across the Mississippi Delta make it difficult to differentiate between subsidence mechanisms and complicate modeling efforts. New data from a nearly 40 m long, 12 cm diameter core taken during the installation of a subsidence monitoring superstation near the Mississippi River, southeast of New Orleans, provides insight into the stratigraphic and geotechnical properties of the Holocene succession at that site. Stratigraphically, the core can be grouped into four units. The top 12 m is dominated by clastic overbank sediment with interspersed organic-rich layers. The middle section, 12-35 m, consists predominately of mud, and the bottom section, 35-38.7 m, is marked by a transition into a Holocene-aged basal peat (~11.3 ka) which overlies densely packed Pleistocene sediment. Radiocarbon and OSL ages are used to calculate vertical displacement and averages subsidence rates as far back as ~3.5 ka, yielding values as high as 8.0 m of vertical displacement (up to 2.34 mm/yr) as obtained from a transition from mouth bar to overbank deposits. We infer that most of this was due to compaction of the thick, underlying mud package. The top ~80 cm of the core is a peat that represents the modern marsh surface and is inducing minimal surface loading. This is consistent with the negligible shallow subsidence rate as seen at a nearby rod-surface elevation table – marker horizon station. Future compaction scenarios for the superstation can be modeled from the stratigraphic and geotechnical properties of the core, including the loading from the planned Mid-Barataria sediment diversion which is expected to dramatically change the coastal landscape in this region. / 1 / Jonathan G Bridgeman

As a result of tunnel construction, the ground level surface above will tend to collapse downward as the soil seeks to refill the missing tubular cavity. Many infrastructures that were originally built on that surface may also fall slightly or severely depending on the engineering design and execution of the tunneling project. Engineers then must factor in the development of ground subsidence, examining geotechnical and geological issues to construct a model that would otherwise predict the extent of vertical settlements. Their predictions could help to assess potential damages and make corrective actions. In this thesis submission, analytical methods from the classical elasticity were used to estimate surface displacements for a prospective tunnel. The analytical equation tied in the method of virtual images originating from Sagaseta with the classical Kirsch elastic solutions for stress-displacements of an infinite plate with hole in order to establish a solution of half-space. This approach will be similar to what Verruijt-Booker had developed after Sagaseta but will include higher-order terms to simulate an excavation process in a longitudinal direction below ground and thereby obtain a new subsidence equation including ground parameters associated with tunnel shape changes occurring at its base, springline (sideway point) and crown (top). These parameters were not previously reported by the Verruijt-Booker work or from current technical literature. In addition, the prescribed solution could include any Poisson’ ratios in which only the original Verruijt-Booker could be found correct for only incompressibility conditions (υ = 0.5). The Verruijt-Booker equation considered deep tunnels only. An extra term influencing the subsidence was included in the modified solution which is significant for shallow tunnels. The derived equations were applied to calculate surface deflections using data from a tunnel construction project to test its viability. Comparison analysis was made with the three methods to be described- Peck, Sagaseta, and Verruijt-Booker. In addition, a parametric study was made to examine the amount of subsidence changed when deciding to construct a tunnel from a shallow to deeper zone. Finally, a qualitative study of the derived equation and Verruijt-Booker was conducted to assess potential subsidence behaviour between shallow and deep tunnels.

Land subsidence is a common phenomenon worldwide. When mitigation has approached a limitation, adaptation becomes an important strategy for sustainable development. Specially, climate variability and changes can make more serious impacts on coastal areas. This study focused on adaptation to land subsidence in Chiangyuan area consisting of several coastal villages, Pingtung county, Taiwan. Little research about the adaptations had been done in this area, except there was some studies for its awareness. Using a case study approach with questionnaires, in-depth interview, direct observation, this study explored past and existed adaptation behaviour in different categories of stakeholders. Moreover, we also tried to analyze the capacity of these adaptation for future impacts from land subsidence and flood made by climate change, and could increase the capacity. The results have revealed local people in Chiangyuan area had abundant experiences on adaptations to land subsidence and flood. They used different kinds of adaptation at same time to cope with flooding, land loss, and salted land problems. The followings have summarized the adaptation of four categories of stakeholders. 1. for local citizen, the major adaptation is house-elevating, who didn¡¦t adopt house elevating were without budget or planning to move out. 2. for farmer, planting economic fruits with higher tolerance to salt-water. 3. for aquaculture, fish-pond elevating, harvesting earlier, or building fish-pond on higher land. 4. for school, using water-proof gates or no classes during flooding. Some suggestion focused on adaptation to land subsidence was also given in this study, specially for government.

As a result of tunnel construction, the ground level surface above will tend to collapse downward as the soil seeks to refill the missing tubular cavity. Many infrastructures that were originally built on that surface may also fall slightly or severely depending on the engineering design and execution of the tunneling project. Engineers then must factor in the development of ground subsidence, examining geotechnical and geological issues to construct a model that would otherwise predict the extent of vertical settlements. Their predictions could help to assess potential damages and make corrective actions. In this thesis submission, analytical methods from the classical elasticity were used to estimate surface displacements for a prospective tunnel. The analytical equation tied in the method of virtual images originating from Sagaseta with the classical Kirsch elastic solutions for stress-displacements of an infinite plate with hole in order to establish a solution of half-space. This approach will be similar to what Verruijt-Booker had developed after Sagaseta but will include higher-order terms to simulate an excavation process in a longitudinal direction below ground and thereby obtain a new subsidence equation including ground parameters associated with tunnel shape changes occurring at its base, springline (sideway point) and crown (top). These parameters were not previously reported by the Verruijt-Booker work or from current technical literature. In addition, the prescribed solution could include any Poisson’ ratios in which only the original Verruijt-Booker could be found correct for only incompressibility conditions (υ = 0.5). The Verruijt-Booker equation considered deep tunnels only. An extra term influencing the subsidence was included in the modified solution which is significant for shallow tunnels. The derived equations were applied to calculate surface deflections using data from a tunnel construction project to test its viability. Comparison analysis was made with the three methods to be described- Peck, Sagaseta, and Verruijt-Booker. In addition, a parametric study was made to examine the amount of subsidence changed when deciding to construct a tunnel from a shallow to deeper zone. Finally, a qualitative study of the derived equation and Verruijt-Booker was conducted to assess potential subsidence behaviour between shallow and deep tunnels.

No description available.

The objective of this study is to examine the thermo-mechanical evolution of the Yorkshire(Cleveland), Sole Pit and East Midland Basins, Southern North Sea using theoretical models of basin formation(subsidence) and basin destruction(inversion).Subsidence occurs in response to a driving tectonic force and is amplified by the input of sediments, which impart a load on the Uthosphere. The form of subsidence varies depending on the degree of crustal and sub-crustal involvement. In order to isolate this driving tectonic subsidence the loading effect of the sediments is removed by backstripping. Intrinsic to the accurate modelling of basin formation using this method are firstly, the presence of a complete sedimentary sequence representing the maximum load on the basement and secondly, a normal and representative compaction trend. Subsidence in the Yorkshire, Sole Pit and East Midland Basins was terminated in the late Cretaceous-early Tertiary by inversion. This inversion is demonstrated to have been controlled by pre-existing structures and accommodated differentially within the Yorkshire and Sole Pit Basins in the form of basement uplift and shortening. A significant proportion of the sediments was removed by this uplift. This is quantified by studying compaction trends and is used to reconstruct the basin configuration prior to inversion to facilitate modelling of basin formation. The patterns of subsidence appear to conform well to those predicted by a model of simple lithospheric stretching with a rapid initial subsidence followed by more gentle thermal and flexural subsidence. Superimposed on this background subsidence are discrete events which appear to be related to periods of active faulting or increases in regional loading(eustatic). Subsidence, like inversion, occurs differentially within the fault bounded margins of the Yorkshire and Sole Pit Basins. The relationship between faults at different crustal levels is complicated by stress partitioning by Permo-Triassic salt horizons, yet it does appear that reactivation of Carboniferous and older structures has influenced the geological evolution of these basins.

No description available.

High extraction mining techniques have produced the need to mitigate and understand ground movements associated with this technology.  Tools such as the Surface Deformation Prediction System (SDPS) facilitate sound scientific decision making in the industry and has continually improved since its inception in 1987.  The capabilities of SDPS have expanded on an as-needed basis.  Currently, the regulatory climate has emphasized the need to understand the impact of underground mining on surface waters, physically and chemically. The SDPS program is used to conduct an analysis of ground movements to assess optimal barrier pillar size for stream protection.  Typical analytical and empirical methods used in mine planning were compared against SDPS methods to ensure the validity and advantage to the use of SDPS for this purpose. Finally, underground mining effects on stream chemistry and health were explored by studying the heavily mined and industrialized watershed of Dumps Creek located in Russell County, Virginia.  This watershed has been identified as being impaired since the Virginia 303(d) List of Impaired Waters was created in 1994.  Currently, there are two pumps staged in the headwaters region of Dumps Creek that help to maintain water levels in an inactive underground mine.  The pumping is necessary to control methane levels that rising water could force into an active underground mine that lies stratigraphically above the inactive mine.  Water is pumped on an as-needed basis and discharges directly into Dumps Creek.  Historic measurements of stream conductivity and benthic health scores were compared to assess whether a correlation exists between the two measurements.  These measurements were compared based on regulatory decisions that emphasized that conductivity is a direct indicator of stream health in all watersheds. Scientific contributions associated with this research include: Further developments in the use of SDPS programming in order to account for stream protection on a case by case basis for both mine panel and surface water protection by optimizing barrier pillar size in relation to a nearby stream; the analysis of available and currently obtained water chemistry data in a mining impacted watershed in attempt to further research to appropriately characterize and mitigate specific problems in order to improve stream health; and, assessment of the complexity of water chemistry impacts from underground mining as related to stream health indicators in different chemically dominated watersheds. / Master of Science

Prediction and control methodologies for ground deformation due to underground mining (commonly referred to as mine subsidence) provide engineers with the means to minimize negative effects on the surface. Due to the complexity of subsidence-related movements, numerous techniques exist for predicting mine subsidence behavior. This thesis focuses on the development, implementation, and validation of numerous enhanced subsidence prediction methodologies. To facilitate implementation and validation, the improved methodologies have been incorporated into the Surface Deformation Prediction System (SDPS), a computer program based primarily on the influence function method for subsidence prediction. The methodologies include dynamic subsidence prediction, alternative model calibration capability, and enhanced risk-based damage assessment. Also, the influence function method is further validated using measured case study data. In addition to discussion of previous research for each of the enhanced methodologies, a significant amount of background information on subsidence and subsidence-related topics is provided. The results of the research presented in this thesis are expected to benefit the mining industry, as well as initiate ideas for future research. / Master of Science

Land subsidence is the gradual settling or sudden sinking of the earth's surface. According to the United States Geological Survey more than 80% of identified subsidence in the United States is a result of groundwater removal. Due to the hydrologic structure and reliance on the Potomac Aquifer, the Southern Chesapeake Bay region of Virginia has suffered from land subsidence since the 1940s. In coastal regions, land subsidence can increase the risk of flooding. This paper presents a mathematical simulation that predicts land subsidence from groundwater pumping. This simulation is used to see how the location of groundwater pumping, as well as the amount of amount of groundwater pumped would differ from two different groundwater pumping policies. The first policy is aimed at limiting land subsidence in the region, while the second policy aims at limiting the damages from land subsidence. These two policies are used to show that a spatially heterogeneous groundwater pumping policy is necessary to minimize the damages from groundwater pumping when land subsidence is present. / Master of Science