Subsidence Model Research Articles

Geochemical and isotopic constraints on the petrogenesis of the Puesto La Peña undersaturated potassic complex, Mendoza province, Argentina: Geodynamic implications

Major and trace element and radiogenic and stable isotope data are reported for the Miocene Puesto La Peña undersaturated potassic complex, located in the Argentine Precordillera. The complex is composed of a pyroxenite core surrounded by a malignite–borolanite association, followed by radial and ring dikes composed of alkaline lamprophyres, tephrite to phonolite and intermediate varieties, porphyritic microledmorite, benmoreite, alkaline trachyte and a swarm of ultrabasic ouachitite dikes. Late trachytic to phonolitic volcanic necks and associated dikes crop out surrounding the malignitic–borolanitic massif.Major and trace element data are consistent with their derivation by partial melting from an enriched, probably lithospheric, metasomatized heterogeneous mantle involving spinel- and garnet-facies mantle sources. The trace element and isotope data indicate that all rock types are derived from a common parental magma and are thus cogenetic.Sr, Nd and Pb variations in the different studied lithologies are restricted, except for the evidence of Sr decoupling in the ouachitite samples. Their Sr–Nd isotope compositions follow the “mantle array” defined by oceanic basalts, within the OIB field, consistent with an intraplate depleted source. The genesis of the ouachitite is interpreted to be related to mixing between asthenospheric magma and melts from the lower lithosphere consisting of K-rich metasomatic layers. The Dupal like Pb isotopes signature suggests a mantle modification by introduction of continental crust material in the upper mantle; this is consistent with the Sr–Nd isotope data from the late silica-undersaturated felsic dikes and volcanic necks.Multistage mantle extraction would have occurred by the end of Neoproterozoic to lower Paleozoic times as indicated by the isotopic data. Partial melting was initiated by mantle upwelling decompression during lithosphere extension. Back-arc extensional conditions during the latest Early Miocene (19Ma), related to the geometry of the Pacific subducted plate beneath the South American plate, favored the tectonic conditions for magma ascent from a magmatic reservoir located at around 30km depth in the crust. A fractional crystallization process, primarily of clinopynoxene, plagioclase, alkali feldspar, nepheline and lesser biotite, magnetite, and apatite, first yielded the cumulate clinopyroxenite, followed by the malignite–borolanite association and the late dikes and volcanic necks. The morphology of the complex, as well as the relationship between their different facies, points to a cauldron subsidence model of emplacement.

Early Paleozoic mafic magmatic events on the eastern margin of the Siberian Craton

Neoproterozoic and Devonian mafic flows, sills and dykes associated with synchronous rifting events are widely distributed along the long-lived Mesoproterozoic to Mesozoic passive eastern margin of the Siberian Craton. Early Paleozoic magmatic events are also present, but are poorly studied, including Early Cambrian volcanic rocks in the Kharaulakh Range and ca. 450Ma age mafic intrusions of the Suordakh event in the Sette–Daban Range. Both suites of early Paleozoic magmatic rocks are characterized by high Ti concentrations (>3wt.% TiO2), ocean island basalt (OIB)-type trace element and rare earth element (REE) patterns, and high εNd(t) values that generally vary between 6 and 9. The Kharaulakh magmas were formed during low degree partial melting of an enriched region of mantle at depths >90km, generating a suite of alkaline basalts. In comparison, the Suordakh magmas were formed during higher degree partial melting of less enriched mantle at depths <90km, forming alkaline to subalkaline basalts. Both suites are characterized by εNd(t) values suggestive of interaction between enriched and depleted magmas and both were emplaced in within-plate tectonic settings. Although Kharaulakh and Suordakh magmatic rocks have relatively small areal extents, significant parts of them are likely hidden below clastic rocks of the Lower Carboniferous–Jurassic Verkhoyansk Complex. The Kharaulakh magmatic rocks may have counterparts in the Canadian Cordillera, that together could be of sufficient scale to define a Large Igneous Province (LIP). Early Cambrian mafic volcanic rocks in the study area are associated with locally distributed terrigenous units in both the Kharaulakh and Sette–Daban ranges, suggesting that this magmatism was related to a rifting event. Modeling of sedimentary basin subsidence in the Sette–Daban area is also supportive of an Early Cambrian rifting event. However, the intrusive rocks associated with the ca. 450Ma Suordakh mafic magmatic event are not related to any rift-related sediments or structures. Contemporaneous granites may be interpreted as silicic magmatism associated with a LIP event.

Integration of field characterisation, mine production and InSAR monitoring data to constrain and calibrate 3-D numerical modelling of block caving-induced subsidence

Block caving often leads to significant ground deformations that if not properly assessed and accounted for may threaten the integrity and safety of overlying mine infrastructure. To mitigate this risk, sophisticated 3-D numerical modelling has been turned to as a means of predicting the extent and magnitudes of caving-induced surface subsidence. However, the complexity of the rock mass interactions involved, coupled with the uncertainty associated with geological heterogeneity, rock mass properties and in-situ stresses results in the need for models to be constrained and calibrated. Results are first presented here from a detailed 3-D back analysis of a caving-induced open pit mine slope failure, used to constrain the rock mass properties and far-field in-situ stresses derived from field characterisation data, as well as to bring understanding to the problem with respect to the cave-pit interactions. The “best fit” set of input properties obtained was then used for forward modelling of caving-induced subsidence for the period 2009–2010. Further calibration of this model was performed using high-resolution InSAR monitoring data. The close fit achieved between the predictive 3-D numerical model and InSAR data demonstrates the promise of InSAR as a means to calibrate sophisticated numerical models, and thereby contribute to managing block caving associated subsidence hazards.

Genesis of the Alpha-Mendeleev and Lomonosov ridges (Amerasian Basin)

In order to specify the origin and evolution of the Alpha-Mendeleev and Lomonosov ridges, profiles of the bottom relief and crustal basement were made. Additionally, the coefficients characterizing the rate of subsidence of the crustal basement in different parts of the ridges for the last 25 Ma were calculated and the depth of the crustal basement prior to the beginning of subsidence in the Early Miocene was estimated. The calculation results were compared with the model of thermal subsidence of the Greenland-Iceland and Iceland-Faroe thresholds, which were also formed by plume-tectonic processes. A large dome rise of the basement was found in the central parts of the Alpha-Mendeleev and Lomonosov ridges. It was also found that the coefficients of thermal subsidence of the crustal basement in the central parts of the Alpha-Mendeleev and Lomonosov ridges are close to those for the Greenland-Iceland and Iceland-Faroe thresholds. It was shown that the depth of the crustal basement prior to the beginning of subsidence in the Early Miocene grew going outwards from the central parts of the ridges, analogous to the present-day pattern. All the information given above indicates the thermal origin of subsidence for the Alpha-Mendeleev and Lomonosov ridges starting from the Early Miocene and the substantial influence of the Arctic Plume on the genesis and evolution of these ridges.

Study on Gradual Deformation and Prediction Model of the Mined Overburden

Based on the overburden three caving feature, the deformation of mining rock process was devided and the criterion of gradual transformation of each stages deformation were given. Then , combined the thin-plate theory, the differential models were derived for rock deformation in level and similar to level bured condition. The boundary condition of each models and exchange condition between different models were put forward and the gradual mechanics model was set up.The subsidence model before roof collapse was solved by Navier double trigonometric series and the deflection surface expression of rock deformation was put forword. At last, the reliability and practicality of the models was verified by engineering examples.

Bearing capacity of single pile and in-flight T-bar penetration for centrifuge modeling of land subsidence caused by the interaction of high-rise buildings

With an increasing number of high-rise buildings in major cities worldwide, land subsidence induced by the interaction between closely-spaced buildings in soft soil areas has become a major challenge for many researchers. The paper considers the interaction of high-rise buildings by determining the bearing capacity of a single pile in the centrifuge model test. The T-bar penetration test was conducted in flight to measure the shear strength of the soft soil, together with vane shear tests when the model had slowed down. By analyzing the relationship curves between land subsidence and the centrifuge acceleration, the allowable bearing capacity of a single pile for the high-rise building was obtained. It is considered that such analysis is a more appropriate method of determining the pile requirements for groups of adjacent high-rise buildings in soft soil areas.

The Moho: Boundary above upper mantle peridotites or lower crustal eclogites? A global review and new interpretations for passive margins

Abstract We have performed a global study of 2D crustal scale wide-angle profiles across passive margins, with regard to local elevations in the Moho which could possibly be interpreted as indicative of lower crustal eclogites. A total of 16 candidates have been found, mainly in the North Atlantic and around Australia. These cases make up c. 6% only of the total profile length studied, confirming the interpretation of the Moho generally representing the top of the mantle. The interpreted candidates for lower crustal eclogites indicate that there may be a link between eclogite bodies and continental suture zones in the Barents Sea, off mid-Norway, in the Newfoundland Appalachians and in the Yilgarn Craton, western Australia. It is also possible that there is a genetic link between the formation of Caledonian eclogites and the Jan Mayen Fracture Zone, which is the only major fracture zone in the North Atlantic. Several of the inferred lower crustal eclogite bodies are located close to lines of major changes in strain, such as coastlines and shelf edges, indicating that lower crustal eclogite bodies may be important in guiding the evolution of basin architecture. Interpreting the Moho beneath the Bedout High on the northwest shelf of Australia as the top of a body of lower crustal eclogites, may imply that the northern termination of the Lambert Shelf represents a paleo suture zone and that the western termination of the Broome Platform acted as a major transfer zone. The significant increase in crustal thickness implied by the eclogite model has important implications for estimates of stretching history, subsidence and hydrocarbon maturation modelling.

Cusp Catastrophe Intelligence Combinatorial Prediction of Land Subsidence

Seeking for a scientific and reasonable predict model is the key point to ensure accurate and reliable prediction results for the land subsidence. In this paper, the research of subsidence area pointed out by picks the process of land subsidence which causes by the water reservoir that conforms to the characteristic of nonlinear dynamics, thus, a new model is established to solve the combinatorial weighted coefficients by using the predict precision, and a simple method is introduced to solve the grey model and neural network combination forecast model. Based on many examples, the new cusp catastrophe land subsidence model is proved to be very effective and much more accurate.

A Mixed Prediction Model of Ground Subsidence for Civil Infrastructures on Soft Ground

The estimation of ground subsidence processes is an important subject for the asset management of civil infrastructures on soft ground, such as airport facilities. In the planning and design stage, there exist many uncertainties in geotechnical conditions, and it is impossible to estimate the ground subsidence process by deterministic methods. In this paper, the sets of sample paths designating ground subsidence processes are generated by use of a one‐dimensional consolidation model incorporating inhomogeneous ground subsidence. Given the sample paths, the mixed subsidence model is presented to describe the probabilistic structure behind the sample paths. The mixed model can be updated by the Bayesian methods based upon the newly obtained monitoring data. Concretely speaking, in order to estimate the updating models, Markov Chain Monte Calro method, which is the frontier technique in Bayesian statistics, is applied. Through a case study, this paper discussed the applicability of the proposed method and illustrated its possible application and future works.

MODELLING OF LAND SUBSIDENCE ALONG TANAH MAS -PELABUHAN SECTION SEMARANG CITY USING FINITE ELEMENT METHOD

Land subsidence has been an apparent problem in the northern part of Semarang city, Central Java, which has caused enormous physical and economical impacts. This area is underlain by alluvium sediments of clay, silt, sand and gravel. The nature of the alluvium soil is soft and highly compressible which induces natural consolidation to occur. The lowering of groundwater table due to exploitation and loads of building and earth fill accelerate the rate of consolidation settlement. A study of land subsidence modeling was carried out in the northern part of Semarang city. Collection and analysis of data on the geology, hydrology, soil properties and monitored settlements were conducted. Modeling of land subsidence involved stress deformation analysis using finite element method. The settlements computed for selected section of the city of Semarang were compared with measurements of settlement in the city area. The simulation results appear to be in reasonably good agreement with the measurement results. Simulation results at selected section indicated that the contribution of lowering groundwater table factor accounts for less than 50% of total monitored subsidence. Meanwhile simulation results using application of external loading and lowering of groundwater table showed better agreement with the monitored subsidence. Information of magnitude and factors causing land subsidence is important particularly for city planning purposes.

Extending dynamic models of mining subsidence

The movement and deformation processes of the overburden strata and ground surface, induced by underground mining, are affected by mining method, spatial relationships, geotechnical conditions of the rock strata and time. The authors reviewed and extended an existing classical prediction model of the dynamic subsidence, and proposed potential new research avenues offered by Cellular Automata (CA) models. The Knothe's influence function model and the significance of subcritical mining geometry were analyzed. The prediction results were verified against the subsidence field survey data to assess their quality and acceptability.

Modeling of Surface Subsidence Based on Time Function

Base on Knothe time function, a new time function was proposed by adding parameter which is approved more accurate in predicting surface subsidence than Knothe funciton. Combing this new time function with section function of surface subsidence basin, a dynamic model is proposed to predict surface subsidence induced by underground mining and a case study based on this model was carried out. The results illustrates this model is more accurate to reflect the dynamic process of surface subsidence

Spatial-temporal characteristics of land subsidence corresponding to dynamic groundwater funnel in Beijing Municipality, China

Due to long-term over-exploitation of groundwater in Beijing Municipality, regional groundwater funnels have formed and land subsidence has been induced. By combining a groundwater monitoring network, GPS monitoring network data, radar satellite SAR data, GIS and other new technologies, a coupled process model based on the dynamic variation of groundwater and the deformation response of land subsidence has been established. The dynamic variation of groundwater funnels and the land subsidence response process were analyzed systematically in Beijing. Study results indicate that current groundwater funnel areas are distributed mainly in the southwest of Shunyi District, the northeast of Chaoyang District and the northwest of Tongzhou District, with an average decline rate of groundwater level of 2.66 m/yr and a maximum of 3.82 m/yr in the center of the funnels. Seasonal and interannual differences exist in the response model of land subsidence to groundwater funnels with uneven spatial and temporal distribution, where the maximum land subsidence rate was about −41.08 mm/yr and the area with a subsidence rate greater than 30 mm/yr was about 1637.29 km2. Although a consistency was revealed to exist between a groundwater funnel and the spatial distribution characteristics of the corresponding land subsidence funnel, this consistency was not perfect. The results showed that the response model of land subsidence to the dynamic variation of groundwater was more revealing when combining conventional technologies with InSAR, GIS, GPS, providing a new strategy for environmental and hydrogeological research and a scientific basis for regional land subsidence control.

Modeling of the three‐dimensional subsidence diffusion–convection problem above a trapdoor

SUMMARYIn a series of previous works, the plane strain and the axisymmetric cases of the so‐called active trapdoor problem have been modeled by virtue of Litwiniszyn's theory of deep subsidence. However, in reality, there exist trapdoor base geometries—in plan view—which can be very well approximated by an elliptical boundary. Following the elliptical shape of the trapdoor, the contour lines of subsidence also appear to be similar ellipses. In this work, an elliptic model of deep subsidence is presented, the mentioned hypothesis of the self‐similar subsidence contour lines is validated, and finally a simplified model is presented. For completeness of the present three‐dimensional model analysis, a rectangular model is also considered. Results are finally presented and compared with those of plane strain and axisymmetric problems. Some suggestions that have been proposed in previous similar works are also evaluated and compared with the results of the present study. Finally, some estimates are proposed for different trapdoor base geometries. Copyright © 2011 John Wiley &amp; Sons, Ltd.

Dynamic Modeling of Surface Subsidence Induced by Underground Mining

A new time function was proposed to cover the disadvantage of knothe time function in predicting surface subsidence by adding parameter k. The velocity and acceleration of the progressive surface subsidence obtained from this new time function were compared with actual subsidence data from an iron mine in China. Combining this new time function with section function of surface subsidence basin, a dynamic mode was proposed to predict surface subsidence induced by underground mining and a case study based on this model was carried out. It shows that this model accurately represents the actual subsidence pattern observed. Instruction

Regional land subsidence model embodying complex deformation

Large regions of land subsidence usually present very complicated historical deformation characteristics of sedimentary layers. A regional land subsidence model based on the modified Merchant model is developed and proposed to describe the visco-elastic-plastic deformation. Regional land subsidence models describing elastic, visco-elastic and elastic-plastic deformations can be derived from the one based on the modified Merchant model by setting proper values of the parameters involved. A new numerical method, the multi-scale finite-element method, is used to model regional land subsidence problems. Land subsidence in Shanghai from 1986 to 1998 is simulated as a case study for the model proposed in this paper. The results show that the model is capable of describing land subsidence with complex deformation characteristics, and can represent the mechanism of land subsidence caused by excessive groundwater withdrawal relatively well. The method is shown to be a good numerical method that significantly reduces computing effort and obtains accurate results.

Modeling visco-elastic–plastic deformation of soil with modified Merchant model

Eighty-four to ninety-eight percent of land subsidence in Shanghai City is caused by the visco-elastic–plastic deformation of sediments. Numerical experiments are done on the sediments with visco-elastic–plastic deformation in Shanghai to verify the modified Merchant model (MM model) and land subsidence model based on the modified Merchant (LS-MM) model. There are two advantages of the MM model and the LS-MM model. One is that only a few parameters are involved. There are three parameters in the MM model and four parameters in the LS-MM model. The other one is that both models can describe elastic, elastic–plastic and visco-elastic deformation in addition to visco-elastic–plastic deformation. The corresponding models are developed by setting proper values of the three parameters of μ, α1 and α2. The two advantages make the LS-MM model flexible and applicable to the simulation of the large regional land subsidence with visco-elastic–plastic deformation and other different kinds of deformation. The results can be improved by variable parameters, especially specific storage.

Sustainable development and utilization of groundwater resources considering land subsidence in Suzhou, China

Suzhou is located at the lower reaches of the Yangtze River in southeastern Jiangsu, China. It is part of the Su-Xi-Chang area including Suzhou, Wuxi and Changzhou. As one of the most developed areas in China, this region has suffered from severe land subsidence caused by extensive groundwater exploitation since 1980s. The land subsidence was controlled by prohibition of groundwater exploration in the past several years. However, the surface water pollution prompted a new task of how to sustainably utilize the groundwater resource, especially to satisfy the emergency demands of water supply. In this paper, we took Suzhou as a representative case to discuss how to develop groundwater resources while controlling the land subsidence. The relationship between the deformation and the groundwater level was analyzed, with focus on the deformation features after the period of groundwater exploitation ban. The results confirmed the conclusion by Shi et al. (2007, 2008a): even in the period of rising groundwater level, same units may manifest different deformation characteristics, such as elasticity, elasto-plasticity, and visco-elasto-plasticity, at different locations of the cone of depression. A land subsidence model that couples a 3-D groundwater model and a 1-D deformation model was developed to simulate the groundwater level and deformation. A high-resolution local grid (child model) for Suzhou was built based on the regional land subsidence model of Su-Xi-Chang area by Wu et al. (2009). The model was used for a number of predictive scenarios up to the year of 2012 to examine how to develop sustainable use of groundwater resources under the conditions of land subsidence control. Our results indicated that about 3.08 × 10 7 m 3/a groundwater could be provided as emergency and standby water source while meeting the land subsidence control target of 10 mm/a.

Long term peatland subsidence: Experimental study and modeling scenarios in the Venice coastland

[1] Land subsidence in drained cultivated peatlands is responsible for a number of serious environmental concerns and economical problems at both the local and the global scale. In low-lying coastal areas it enhances the risk of flooding, the saltwater contamination of shallow aquifers, and the maintenance costs of the systems that help keep the farmland drained. Since the subsidence is a major consequence of the bio-oxidation of the soil organic fraction in the upper aerated zone, cropped peatlands in temperate and tropic regions are important sources of CO2 into the atmosphere. A 4-year long experimental study has been performed in a drained peatland located south of the Venice Lagoon, Italy, to help calibrate a land subsidence model developed to predict the expected behavior of the ground surface elevation. Continuous monitoring of the hydrological regime and land displacements shows that the vertical movement of the peat surface consists of the superimposition of daily/seasonal time-scale reversible deformations related to soil moisture, depth to the water table, and temperature fluctuations, and long term irreversible subsidence due to peat oxidation. A novel two-step modeling approach to separate the two contributions from the available observations is presented. First, the elastic component is computed by integrating the peat vertical deformations evaluated by a constitutive relationship describing the porosity variation with the moisture content and pore pressure changes implemented into a variably saturated flow equation-based numerical code. The observed trend is then filtered from the computed reversible displacement and is used to calibrate an empirical relationship relating land subsidence rate to drainage depth and soil temperature. The results show that in recent years the subsidence rate ranged from 3 to 15 mm a−1. The large variability is due to the different climate conditions underlying the monitoring period, in particular a wet 2002 and a very dry 2003. The model is then used to investigate the effect of human activities and climate change on the expected reduction of the peat thickness. The results suggest that the long term subsidence is mainly controlled by the manner in which the water table is managed in the peatland. For example, the subsidence rate is almost halved if the current 0.5 m mean water table depth is kept at 0.2 m. Conversely, even the extreme warning scenario provided by the IPCC in 2007 do not suggest significant changes on the expected subsidence trend, at least in low lying reclamation areas where the average temperature rise should not be accompanied by a significant reduction of water availability.

Integration of a subsidence model and SAR interferometry for a coal mine subsidence hazard map in Taebaek, Korea

Coal mine subsidence hazard can be effectively evaluated by geographic information system (GIS) analysis if sufficient data is provided. It is, however, difficult to obtain ground-based data, especially in remote and less populated mining areas. In this study, we construct and validate a coal mine subsidence hazard map in Taebaek, Korea, by integration of space-borne L-band synthetic aperture radar (SAR) measurements and a fuzzy-based subsidence model. There is an approximately 15-year time interval between the radar measurements used for the subsidence hazard model and those used to validate the subsidence. A subsidence hazard map was constructed using Japanese Earth Resources Satellite (JERS-1) SAR data from the early 1990s and the subsidence model. For the coal mine subsidence hazard mapping, a certainty factor analysis was used to estimate the relative weights of four control factors influencing coal mine subsidence, and the relative weight of each factor was then integrated to produce a subsidence hazard index by a fuzzy combination operator. The predicted hazard areas were then investigated and validated by comparison with subsidence occurrences observed by Advanced Land Observing Satellite Phased Array type L-band Synthetic Aperture Radar (ALOS PALSAR) interferometry in 2007–2008. The results showed a good agreement between the predicted locations vulnerable to subsidence and the actual subsidence occurrences with a prediction accuracy of about 73% and a root mean square error of about 0.35. These results demonstrate that a map produced by integration of a subsidence model and SAR interferometry can be used to predict and monitor coal mine subsidence hazards, especially in remote regions.