Surface subsidence is an inevitable consequence of most underground coal mining. The United States Bureau of Mines has estimated that over 3,000 square miles of land in this country have been affected by subsidence, and it is currently estimated that an additional 2,400 to 3,800 square miles will be affected over the next twenty years. Surface subsidence is a complex phenomenon which is influenced by many variables related to both mining and site conditions. Although it cannot be prevented, foreigh experience has shown that it, nevertheless, can be controlled. In order to achieve this goal, however, methods of subsidence prediction and control must be developed for the United States mining conditions and justified with empirical data. The objective of this research is to develop characteristic relationships of longwall subsidence and its related parameters from case studies gathered from the Appalachian coalfields. Furthermore, based on this information, an empirical, predictive capability will be developed which can be used to provide accurate and reliable predictions of subsidence in this region. / Master of Science

天津是中國遭受地面沉降最嚴重的城市之一。由於經濟與城市化的快速發展，新的沉降中心陸續出現在天津的郊區城鎮。本文結合L-和X-波段合成孔徑雷達(Synthetic Aperture Radar, SAR)資料，利用雷達干涉測量(SAR Interferometry, InSAR)時間序列分析，旨在加強天津郊區的沉降監測能力。先進的基於SAR資料的遙感技術，永久散射體干涉測量(Permanent Scatterers, PS)技術被證明是一種有效的，大範圍的，低成本的沉降監測手段。 / 工作在X波段(波長為3.1cm)的TerraSAR (TSX)衛星可以提供新一代具有高解析度(1米)和短重放週期(11天)的SAR資料，從而能夠更快的獲取適用於干涉的時間序列的資料，並且適用於單個建築物的沉降觀測。然而，利用X-波段在森林或植被覆蓋區域並不能得到有效資訊。ALOS衛星的SAR感測器工作在L波段，由於波長更長(波長為23cm)，穿透力更強，所以在植被覆蓋區域也具有良好的相干性。但是ALOS衛星的SAR資料解析度更低(7米)，重放週期更長(46天)。從這兩個波段的資料特徵來看，他們可以被認為是互補的。所以，結合這兩個波段的資料可以增強沉降監測的能力和提供更為可靠的結果。儘管ALOS衛星於2011年4月22日停止了工作，我們的研究結果仍然可以為結合不同波段的SAR資料進行沉降監測提供普遍適用的結論，並為以後的研究工作提供參考。 / 在研究中，我們提出了結合L和X波段的InSAR時間序列分析策略。此策略不僅可以作為X波段資料最優化獲取方案，而且可以成為快速，高精度，低成本，多級，大範圍監測策略。 / 其次，我們基於多時序SAR資料，利用PS和准PS(Quasi-PS, QPS)技術進行了L波段與X波段的沉降監測能力探尋。L波段和X波段的時間序列分析所得到的沉降模式有很好的吻合性，都監測出三個主要的沉降中心，其中包括一個新近發現的沉降中心位於南河鎮。 / X波段的PS分析結果顯示出高密度的PS點，證實了它可以用於同時監測星狀分佈的多個城鎮。結果也表明了高解析度TSX資料可以監測到線狀地物如鐵路，高速公路以及電力線的細節資訊和沉降資訊，這些可以成為高解析度PS技術在中國的重要應用。 / 除此之外，我們利用水準資料驗證了L和X波段的處理結果，並且對地面沉降的過程進行了研究。由於水準資料和PS監測結果在時間和空間維上的採樣差別很大，所以我們對這兩者比較所具有的不確定性進行了詳細分析。結果表明了這兩種監測資料具有很好的一致性。 / 最後，我們發現在天津抽取地下水是引起地面沉降的一個主要原因。根據PS結果和地質資料，我們發現地質因素可能是另一個用於解釋沉降中心位置和形狀的原因。 / The aim of this dissertation is to enhance the capability of monitoring subsidence in Tianjin suburbs by combining L- and X-band Synthetic Aperture Radar (SAR) data with Interferometry (InSAR) time series analysis. Tianjin is located in one of the major subsidence regions in China and several new subsiding centers have been found in the suburbs of Tianjin. Advanced remote sensing technique, Permanent Scatterers (PS) based on SAR data has been found to be a feasible way to detect and monitor wide area ground subsidence at a low cost. / TerraSAR X-band (TSX) of short wavelength (3.1 cm) provides new generation SAR data with high spatial resolution of 1 m and short revisit period of 11 days. It maintains the capability to fast build up interferometric stack, and to measure the subsidence of individual features, while almost no information can be detected with X-band in the forested and vegetated areas. ALOS L-band signal of longer wavelength (23cm) penetrates deeper into the vegetation cover and depicts higher coherence over non-urban areas, while the spatial resolution is relatively lower (7m) and revisit time is longer (46 days). The characteristics of these two bands can be regarded as complementary. Combining L- and X-band can enhance abilities of subsidence monitoring and provide more reliable results. Although ALOS died on April 22, 2011, this research work will provide general answers for combining different bands of SAR data to monitor subsidence, and give suggestions for future research work. / In this research work, we have developed the strategy of combining L- and X-band with InSAR time series analysis. This strategy can not only be an optimized X-band acquisition plan, but also be a multi-level wide area monitoring strategy of subsidence with fast extraction, high precision and low cost. / Moreover, with multi-temporal SAR data, we also investigate monitoring abilities of L- and X-band by exploring PS and Quasi-PS (QPS) techniques. The subsidence patterns derived from L- and X-band InSAR time series analysis are observed to have a good agreement. Three severe land subsidence zones were detected, containing one newly discovered subsiding center located in Nanhe Town. / The X-band PS analysis shows high density of PS points and confirms its strong ability for simultaneously monitoring subsidence over star-like-distributed multiple towns. The results also demonstrate that linear constructions such as railways, highways and power lines can be detected in detail with high resolution TSX SAR data and indicates the deformation monitoring capability for large-scale man-made linear features which is a key application in China. / Furthermore, L- and X-band results were independently validated with leveling data and ground motion processes were studied. The uncertainties were comprehensively analyzed between PS results and ground leveling data, whose densities are very different in both spatial and temporal domains. The overall results show a good agreement with each other. / Finally, we find that underground water extraction is one of the major reasons for ground subsidence in Tianjin. In addition, with the integrated analysis of the PS results and the geological data, we found that lithological characteristics may be another important reason to explain location and shape of the subsiding centers. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Luo, Qingli. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2013. / Includes bibliographical references (leaves 103-112). / Abstract also in Chinese. / Abstract --- p.I / TABLE OF CONTENT --- p.VI / List of Figures --- p.VIII / List of Tables --- p.XI / List of abbreviations --- p.XII / ACKNOWLEDGEMENT --- p.XIV / Chapter 1 --- INTRODUCTION --- p.1 / Chapter 1.1 --- Thesis contributions --- p.6 / Chapter 1.2 --- Thesis structure --- p.7 / Chapter 2 --- BACKGROUND --- p.9 / Chapter 2.1 --- Synthetic Aperture Radar (SAR) --- p.9 / Chapter 2.1.1 --- SAR imaging geometry --- p.9 / Chapter 2.1.2 --- SAR satellites --- p.10 / Chapter 2.2 --- Synthetic Aperture Radar Interferometry (InSAR) --- p.13 / Chapter 2.2.1 --- Introduction --- p.13 / Chapter 2.2.2 --- Principles of InSAR --- p.13 / Chapter 2.3 --- Differential Synthetic Aperture Radar Interferometry (D-InSAR) --- p.18 / Chapter 2.3.1 --- D-InSAR principle --- p.18 / Chapter 2.3.2 --- The advantages and Limits of interferometric measurements --- p.21 / Chapter 2.4.3 --- The development of PS technique --- p.22 / Chapter 2.4 --- Persistent Scatterers Interferometry (PSI) --- p.24 / Chapter 2.4.1 --- Permanent Scatterers (PS) Technique and Advantages --- p.24 / Chapter 2.4.2 --- Principle of PS technique --- p.26 / Chapter 2.5 --- QPS (Quasi-PS) Interferometry --- p.28 / Chapter 3 --- MULTI IMAGES INSAR ANALYSIS OF TIANJIN --- p.31 / Chapter 3.1 --- Introduction --- p.32 / Chapter 3.2 --- Study area and SAR data --- p.34 / Chapter 3.3 --- X-band optimized acquisition planning combing with L-band --- p.38 / Chapter 3.3.1 --- The strategy --- p.38 / Chapter 3.3.2 --- Experimental results and analyzes --- p.40 / Chapter 3.4 --- Estimating deformation maps with L- and X-band --- p.45 / Chapter 3.4.1 --- Monitoring subsidence over multiple towns and large man-made linear features with X-band --- p.45 / Chapter 3.4.2 --- The L-band QPS Results --- p.56 / Chapter 3.5 --- Conclusions --- p.58 / Chapter 4 --- VALIDATION AND INTERPRETAION --- p.61 / Chapter 4.1 --- Introduction --- p.61 / Chapter 4.2 --- Validation --- p.61 / Chapter 4.2.1 --- Leveling data --- p.61 / Chapter 4.2.2 --- Uncertainties analysis --- p.64 / Chapter 4.2.3 --- Average velocity comparison --- p.66 / Chapter 4.2.4 --- Annual displacement comparison --- p.68 / Chapter 4.2.5 --- Deformation time series: InSAR results and leveling --- p.70 / Chapter 4.2.6 --- Average velocity map comparison between InSAR results and leveling --- p.71 / Chapter 4.2.7 --- Displacement comparison between InSAR results and GNSS data --- p.73 / Chapter 4.2.8 --- Average velocity comparison between ALOS results and leveling --- p.73 / Chapter 4.3 --- Geological Interpretation --- p.74 / Chapter 4.4 --- Field survey --- p.77 / Chapter 4.5 --- QPS points analysis with aerophotograph --- p.81 / Chapter 4.6 --- Conclusions --- p.84 / Chapter 5 --- VALIDATION ALONG RAILWAY --- p.87 / Chapter 5.1 --- Introduction --- p.87 / Chapter 5.2 --- Study area --- p.87 / Chapter 5.3 --- The validation plan --- p.87 / Chapter 5.4 --- Validation with leveling data --- p.89 / Chapter 5.4.1 --- Leveling data --- p.89 / Chapter 5.4.2 --- The average subsidence rate comparison --- p.91 / Chapter 5.4.3 --- The displacement comparison --- p.95 / Chapter 5.5 --- Conclusions --- p.97 / Chapter 6 --- SUMMARY --- p.98 / The Publications --- p.102 / REFERENCES --- p.103

Beach shoreline retreat induced by coseismic subsidence in the Cascadia subduction zone is an important post-earthquake hazard. Sand on a beach acts as a buffer to wave attack, protecting dunes, bluffs and terraces. The loss of sand from a beach could promote critical erosion of the shoreline. This study was initiated in order to estimate the potential amount of post subsidence shoreline retreat on a regional scale in the Central Cascadia Margin. The study area is a 331 km stretch of coastline from Copalis, Washington to Florence, Oregon. Several erosion models were evaluated, and the Bruun model was selected as the most useful to model shoreline retreat on a regional scale in the Central Cascadia Margin. There are some factors that this model does not address, such as longshore transport of sediment and offshore bottom shape, but for this preliminary study it is useful for estimating regional retreat. The range of parameter input values for the Bruun model include: the depth of closure (h) range from 15 m to 20 m water depth; the cross-shore distance (L) range from 846 m to 5975 m; and the estimated subsidence amount (S) range from O m to 1.5 m. The minimum to maximum range of post-subsidence shoreline retreat is 142 to 531 m in the Columbia River cell, 56 to 128 m in the Cannon Beach cell, 38 to 149 m in the Tillamook cell, 25 to 91 m in the Pacific City cell, 11 to 126 m in the Lincoln City cell, 30 to 147 m in the Otter Rock cell, 0 to 165 m in the Newport cell, 0 to 76 m in the Waldport cell, and 0 m in the Winchester cell. Results of the study suggest that many of the beaches in the study area are at risk of beach and personal property loss. Beach communities could limit the amount of potential damage in these areas through coastal zone planning.

A field test is developed to assess the collapse susceptibility of soils rapidly and inexpensively. The in situ collapse test device measures the vertical deformations which occur in soils when they are subjected to stress and given access to water while under continuous load. Principles of statistics were employed to show that laboratory testing of soil specimens overestimate the magnitude of collapse as measured in the field and that the magnitude of collapse is, in part, a function of the soil moisture content at the time of loading and at the time of collapse. Good correlation was found between the spatial variability of collapsible soils with the location of alluvium terrace deposits and structurally damaged buildings.

A research report submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the Degree of Master of Science in Engineering, 2016 / Previously undermined areas pose a significant challenge to mining by opencast due to the risk of sinkhole occurrence. In order to optimise reserve utilisation as well as safeguard personnel and equipment there was need to develop a “Sinkhole Prediction Model” to assist in the prediction of areas prone to sinkhole formation. The aim of this research therefore was to develop a “Sinkhole prediction tool” with a view to pre-identifying areas of potential sinkhole hazard to inform better controls to assist in mining these areas safely. This was done utilising the current Hill (1996) caving height method culminating in the development of a hazard index model dividing the mining zones into high and low hazard. These areas were colour coded Red (High hazard) and Green (Low Hazard). The “Sinkhole Prediction Model” evolved to include over hundred sinkhole incidences that were statistically analysed to firm up on the robustness of the Prediction Model capabilities. The Hill (1996) caving height formula was discounted after the statistical analysis indicated that a good prediction model lies in the interrogation of site specific data. The outcome of the work conducted in this research report indicated a 97% correlation between the refined “Sinkhole Prediction Model” and the actual sinkhole occurrence at the Anglo American case study area (Mine X). Various refinements inclusive of lithological assessments, blast and drilling reconciliations as well as the implementation of the roughening up quality audits led to the implementation of a robust sinkhole management process that has managed to consistently assist in safeguarding equipment and personnel thus allowing for coal extraction optimisation in areas that could have been written off due to the sinkhole hazard. This risk can only be eliminated by mining the areas with the sinkhole risk. Currently the method is being impacted by significant roughening up cost incurred in a drive to make the areas safe to allow for coal extraction. The roughening up process on average costs R3.5 million per sinkhole and is a function of the number of sinkholes found, which translates to an equivalent cost of R7 / sales tonne. The current sinkhole prediction model being employed in deficient in that it cannot pinpoint the actual location of the void in the area previously undermined by bord and pillar and this is a great limitation of this report. Various geophysical techniques were pursued to assist in the precise identification of the actual sinkhole spatially. This process was aimed to reduce the roughening up cost (entire block stabilisation) as opposed to targeted sinkhole excavation and stabilisation. This process proved futile as the void identification systems are highly incapable of identifying the voids / iv sinkholes spatially (x, y and z coordinates) to assist targeted sinkhole treatment as a result of the following:  System inability to penetrate areas comprised of highly conductive strata such as clays.  Inability to distinguish between the underground voids and geological anomalies such as dykes.  Not suitable for penetrating wet strata.  Impacted by noise interference from mining machinery. The major result of this research is the establishment of a site specific “Sinkhole Prediction Model” that can generate hazard plans in real time thus informing the management on areas associated with a potential sinkhole hazard. The hazard plans can be generated timely and decisions made to facilitate safe coal extraction in areas of high sinkhole hazard. This has culminated in a robust sinkhole management process within the group that has managed to eliminate the risk of personnel and equipment exposure at Mine X. The roughening up process is accepted as the primary sinkhole mitigation or rehabilitation process with the need to work towards reducing the roughening up costs through development of the tool capable of precisely identifying the voids routinely to facilitate targeted rehabilitation. Significant research is required in this area as the mining environment is comprised of strata that currently cannot support the use of real time void identification to facilitate targeted void identification and rehabilitation. There is also merit in the future to formulate the database capable of assisting in the prediction of sinkholes in the Witbank coalfield as well as assist in robust management of mining boundaries across the different mining houses. The system implemented at Mine X is currently being deployed to other operations in the group where modification will be made to match the site specific conditions. Future research into understanding the sinkhole occurrence dynamics is quite crucial if targeted rehabilitation is to be achieved for cost reduction and mining sustainability. A combination of the understanding of the sinkhole occurrence driving mechanisms in conjunction with use of modelling packages such as ELFEN (a hybrid Modelling) tool will go a long way in enhancing the development of precise sinkhole prediction point in space.

Ground-water pumping has led to subsidence and many earth fissures in unconsolidated alluvial basins in Arizona. Earth fissures result from tensile failure; however, mechanisms producing the tensile forces are not well understood. Horizontal displacement measurements (opening and closing) of seven earth fissures were made semi-monthly during 1976 to 1982 in the lower Santa Cruz Basin and Avra Valley. Permanent and temporary short-base extensometers with a resolution of ±2.54 μm were developed and perfected which use dial gauges and transducers. Among different fissure movements, the greatest total was 41.44 mm, the greatest single opening was 31 mm, and exclusive of that, the greatest net opening was 16.54 mm. Fissures opened and closed repeatedly, exhibiting smooth movements over long periods of time, punctuated by sudden jumps. Generally, old and new earth fissures exhibited similar behavior. Earth fissures tend to close after long, dry periods and to open after heavy rainfalls. The earth fissure with the greatest movement was closest to the area of the greatest subsidence.

Thesis (Ph.D.)--University of Wollongong, 2009. / Typescript. Includes disc in back pocket. Includes bibliographical references: leaf 264-272.

No description available.

M.Tech. (Extraction Metallurgy) / The discovery of gold at Langlaagte in 1886 led to the development of gold mining in the Far West Rand in 1934. When shafts were sunk, water from the dolomites posed a serious threat to mining. Despite cementation that sealed the many fissures, water still found its way into the underground workings. This led to the “uniform” policy of dewatering. The farming communities in the area that were dependent on the ground water had to be considered, as they had lost their livelihood. As the water levels lowered, dolines and sinkholes were formed, posing a serious threat to life and property. When the mines eventually cease to operate, be it due to high working costs, or the declining grade of the ore body, the re-watering of the dolomitic compartments will occur as a natural consequence. When water comes to within six metres of the original water level, ground instability, the formation of dolines and sinkholes, both new and existing, will occur, threatening the important rail link between Pretoria and Cape Town as it passes through Far West Rand, as well as the N12 between Johannesburg and Potchefstroom, as well as the N14 which lies to the east connecting the Gauteng Province and the North West Province. The dewatering of the compartments caused the soil which formed the roof of the cavities to dry. Re-watering will cause this dry, stable material to become wet and unstable. Where mixtures of slime and/or other material, which is not part of the geological composition of that area was used, the same phenomenon will apply. A further complication is caused by the slimes dams which are unlined. In fact, some of the slime dams were deliberately constructed over cavernous dolomite. This large mass of mine tailings over the dolomitic aquifers will “liquefy”. If the re-watering is not carefully managed the rising water table will undoubtedly trigger a rash of new sinkholes, with catastrophic consequences for unsuspecting communities that may have been established in sensitive areas. The results of previous investigations by the Departments Minerals, Energy and Water Affairs who, due to the loss of institutional memory, might not be able to find the relevant information. Other organizations such as the Council for Geoscience could be using the results for consultancy. The information should be digitized and be available to the broader South African public. FWRDWA is currently in charge of monitoring events in the area. Levelling observations have been carried out quarterly and, so far the movement of ground is minimal. The potential hazard of ground instability will recur with the re-watering of the dolomitic compartments of the Far West Rand. To support what could happen, reference is made to events which took place in the late seventies when the Far West Rand had an above average rainfall. The Donaldson Dam overflowed into the Wonderfontein Spruit and into the dewatered Venterspost compartment. As a result, the water level of the Venterspost Compartment rose rapidly which led to the re-activation of sinkholes and the formation of new ones in the Venterspost area. In the present work levelling has been carried out along most of the loops affected and the results of the levelling give an impression that the surface is currently relatively stable. This Dissertation is presented as an attempt to alert the authorities to the potential dangers if the post mining period is not carefully monitored and insufficient provision made to deal with potential contingencies.