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The smectite dehydration theory developed by Ransom and Helgeson was applied for simulation of land subsidence in the Yun-Lin
coastal area, Taiwan. The volumetric reduction of smectite clay at equilibrium state was computed by assuming that the dehydration
of interlayer water in smectite clay can be described with a regular solid solution reaction...
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Context 1
... Yun-Lin coastal area, located in the southwestern coastal region of Taiwan, is in the southern part of the terrain of the Chuoshui River alluvial fan and between the new and old Huwei Rivers (see Fig. 1). The terrain is fairly flat with a ground surface elevation of 0-3 m above sea level. The compositions of the sediments are uncon- solidated sand, gravel, silt, and clay, with a total depth of over 2 km in the Chuoshui River alluvial fan. The compo- sitions and structure of the geological environment in this area are also ...
Citations
... Land subsidence is mainly induced by the compaction of clay caused by a decrease in pore water pressure (Calderhead et al., 2011;Hung et al., 2012;Lin et al., 2015;Liu et al., 2004b;Liu et al., 2001;Phien-Wej et al., 2006). The distribution of the clay layer largely affects the groundwater flow system; the distribution of clay interbeds is the main compaction material of land subsidence (Calderhead et al., 2011;Liu et al., 2004a;Liu et al., 2001;Zhu et al., 2015). ...
... Land subsidence is mainly induced by the compaction of clay caused by a decrease in pore water pressure (Calderhead et al., 2011;Hung et al., 2012;Lin et al., 2015;Liu et al., 2004b;Liu et al., 2001;Phien-Wej et al., 2006). The distribution of the clay layer largely affects the groundwater flow system; the distribution of clay interbeds is the main compaction material of land subsidence (Calderhead et al., 2011;Liu et al., 2004a;Liu et al., 2001;Zhu et al., 2015). Gravel and coarse sand can form preferential paths for groundwater flow and silt and clay can serve as a barrier. ...
The distribution of hydrogeological materials in a three-dimensional heterogeneous aquifer system has a large effect on groundwater flow and land subsidence simulations. The hydrogeological information for regions between boreholes embeds a large amount of uncertainty into the hydrogeological model, and thus affects numerical assessment. Quantifying the effects of the heterogeneous system and hydrogeological model uncertainty on groundwater flow and land subsidence simulations is thus important. Here, data from 46 geological boreholes in Huwei Town, Taiwan, were adopted to investigate hydrogeological model uncertainty. The one-dimensional continuous-lag Markov chain and the geostatistical method were used to analyze the spatial characteristics of hydrogeological materials and generate realizations of the hydrogeological model based on the assessment results. Estimated hydrological conditions and hydraulic parameters were applied to mitigate uncertainty not caused by the hydrogeological model. The mean of the results of land subsidence in Monte Carlo simulations showed a more stable distribution than that of individual realizations, for which land subsidence might be far from the mean. Therefore, the mean and variance results provide a reliable assessment with uncertainty information for land subsidence simulations. The coefficient of variation (CV) was used to quantify the hydrogeological model uncertainty. The CV value of land subsidence was larger than that of the hydraulic head because the thickness of clay is not uniform whereas the flow pattern is smooth. The variance and CV distributions of the hydraulic head and land subsidence provide uncertainty information that can be used to guide site investigations. A heterogeneous hydrogeological model with uncertainty quantification should be carefully applied to land subsidence simulations to obtain reasonable results.
... These aquifers are connected in the proximal fan. The second aquifer spans almost the entire CRAF and is the primary aquifer for withdrawing groundwater because this aquifer has the depth for economic water extraction and is the thickest [29,31,32]. According to previous studies, the middle and the distal fans are covered with more than 250,000 pumping wells, but these two fans are composed of highly compressible materials [33]. ...
Land subsidence is a significant problem around the world that can increase the risk of flooding, damage to infrastructure, and economic loss. Hence, the continual monitoring of subsidence is important for early detection, mechanism understanding, countermeasure implementation, and deformation prediction. In this study, we used multiple-sensor observations from the Continuous Global Positioning System (CGPS), the small baseline subset (SBAS) algorithm, interferometric synthetic-aperture radar (InSAR), precise leveling, multi-layer compaction monitoring wells (MLCWs), and groundwater observation wells (GWs) to show the spatial and temporal details of land subsidence in the Choushui River alluvial fan (CRAF), Taiwan, from 1993 to 2019. The results showed that significant land subsidence has occurred along the coastal areas in the CRAF, and most of the inland subsidence areas have also experienced higher subsidence rates (>30 mm/yr). The analysis of subsidence along the Taiwan High Speed Rail (THSR) revealed a newly formed subsidence center between Tuku and Yuanchang Townships in Yunlin, with high subsidence rates ranging from 30 to 70 mm/yr. We propose a map showing, for the first time, the distribution of deep compactions occurring below 300 m depth in the CRAF.
... A wide range of geological surveys was indispensable to the construction work, since most of the THSR piles were constructed on the Choshui River Alluvial Fan (CRAF), which is composed of sediments such as metamorphic quartzite, slate, sandstone and mudstone (Tung and Hu, 2012). According to Liu et al. (2001), the CRAF is formed by four interlaying aquifers and four aquitards (see also Ge et al., 2010) (Figure 1). Their surveys pointed out that aquifers underneath the CRAF are filled with porous and permeable sandy materials. ...
In 2011, thousands of Taiwanese farmers gathered in Yunlin County to protest against a government environmental management programme which attempted to address the land subsidence that has threatened Taiwan’s High-Speed Rail infrastructure. New environmental monitoring technologies have been developed to deal with the land subsidence but these have, simultaneously, provoked contestation. The dispute indicates that the horizontalism inherent in traditional studies of geopolitics fails to account for the politics of verticality. Indeed, recent work on volumetric politics opens up new horizons for thinking about the exercise of power through three dimensions; the geopolitics of the underground have remained untheorised. Moreover, the existing literature on volume also fails to account for the chaotic state of the material world. From the perspective of assemblage thinking, I outline three characteristics which shape the ‘geopolitics of land subsidence’. From this standpoint, this paper argues for a geographical approach to subterranean politics which puts more emphasis on volume, emergence and matter. With reference to ethnographical fieldwork conducted in scientific laboratories and in Yunlin County, I demonstrate how subterranean materials continuously frustrate the state’s volumetric practices. By problematising the geopolitics of land subsidence, this paper also advances the understanding of political geology, which is seeking to ‘decolonise’ and ‘pluralise geological thought’.
... Both the agricultural and anthropogenic activities have resulted in deterioration of water quality that rendering serious threats to human beings [3]. The over-pumping of groundwater for aquaculture leads to land subsidence, seawater intrusion, and soil salinization [4]. Over-pumping also introduces excess dissolved oxygen that may oxidize the immobile mineral, and increases their concentration in water. ...
... The electrical conductivity (EC, μS cm-1) is a useful tool to evaluate the purity of water and a good measure of salinity hazard to crops. Electrical conductivity values of groundwater samples ranged between 754 and 8944 μS cm-1, Table (4). The result indicates that almost the groundwater samples crossed the permissible limits of the WHO and GSS except that of the wells in EH7 and BH8 sites. ...
... The maximum desirable limit of chloride for drinking water is specified as 200 mg L -1 while the maximum permissible limit is 600 mg L -1 . The chloride concentration values of 5 samples fall within the allowable limits of GSS standards, while the four samples HF1, ZZF5, HJ6, and TE9 crossed the GSS guidelines, Tables (3,4). ...
... Compaction of unconsolidated sediment under its own weight or owing to overburden loading can also cause coastal subsidence ( fig. 1a, bottom right); this is often a dominant factor in major depocentres 19,[87][88][89][90] . When sediment accretion leads to an increase in effective stress, pore fluid is expelled, causing hydrostatic compaction [91][92][93] . ...
Coastal subsidence contributes to relative sea-level rise and exacerbates flooding hazards, with the at-risk population expected to triple by 2070. Natural processes of vertical land motion, such as tectonics, glacial isostatic adjustment and sediment compaction, as well as anthropogenic processes, such as fluid extraction, lead to globally variable subsidence rates. In this Review, we discuss the key physical processes driving vertical land motion in coastal areas. Use of space-borne and land-based techniques and the associated uncertainties for monitoring subsidence are examined, as are physics-based models used to explain contemporary subsidence rates and to obtain future projections. Steady and comparatively low rates of subsidence and uplift owing to tectonic processes and glacial isostatic adjustment can be assumed for the twenty-first century. By contrast, much higher and variable subsidence rates occur owing to
compaction associated with sediment loading and fluid extraction, as well as large earthquakes. These rates can be up to two orders of magnitude higher than the present-day rate of global sea- level rise. Multi-objective predictive models are required to account for the underlying physical processes and socio-economic factors that drive subsidence.
... Compaction of unconsolidated sediment under its own weight or owing to overburden loading can also cause coastal subsidence ( fig. 1a, bottom right); this is often a dominant factor in major depocentres 19,[87][88][89][90] . When sediment accretion leads to an increase in effective stress, pore fluid is expelled, causing hydrostatic compaction [91][92][93] . ...
A correction to this paper has been published: https://doi.org/10.1038/s43017-020-00134-8.
... On the other hand, the hydrological mass loading by groundwater, free surface water, soil moisture, and snow is considered as an important factor for the seasonal surface displacement recorded in GNSS (Global Navigation System) time respectively. According to previous investigations [2,42,43], this alluvial fan is composed of unconsolidated sediments, mainly gravel, sand, and clay. The sediments originate from rock formations in the Western Foothills and the Central Range, including slate, shale, metamorphic quartzite, sandstone, and mudstone ( Figure 1). ...
... Based on sedimentological data, the alluvial fan of the Choshui River can be divided into four aquitards and four aquifers at depths from 0 to 300 m. Figure 2b shows a conceptual hydrogeological model of the alluvial fan of the Choshui River. The four aquifers are essentially connected in the head of the alluvial fan [43]. Aquifer 2 (labeled as F2) is the thickest and largest among the four aquifers, with an average thickness of about 95 m. ...
... Aquifer 2 (labeled as F2) is the thickest and largest among the four aquifers, with an average thickness of about 95 m. Previous studies demonstrated that most groundwater resources are pumped from Aquifers 2 and 3 [2,33,42,43]. The annual rainfall is approximately 1200-2000 mm in the area. ...
Balancing the demand of groundwater resources and the mitigation of land subsidence is particularly important, yet challenging, in populated alluvial fan areas. In this study, we combine multiple monitoring data derived from Multi-Temporal InSAR (MTI), GNSS (Global Navigation Satellite System), precise leveling, groundwater level, and compaction monitoring wells, in order to analyze the relationship between surface displacement and groundwater level change within the alluvial fan of the Choshui River in Taiwan. Our combined time-series analyses suggest, in a yearly time scale, that groundwater level increases with the vertical surface displacement when the effect of pore water pressure dominates. Conversely, this relationship is negative when the effect of water-mass loading predominates over pore water pressure. However, the correlation between the vertical surface displacement and the groundwater level change is consistently positive over the time scale of two decades. It is interpreted that the alluvial fan sequence in the subsurface is not fully elastic, and compaction is greater than rebound in this process. These findings were not well reported and discussed by previous studies because of insufficient monitoring data and analyses. Understanding the combined effect of groundwater level change and vertical surface displacement is very helpful for management of land subsidence and usage of groundwater resources. The spatial and temporal integration of multi-sensors can be applied to overcome the limitations associated with the single technique and provides further insights into land surface changes, particularly in highly populated alluvial fan areas.
... Clays are known to correlate with subsidence, depending on the amount, type, and moisture content of the clay (Bull, 1964;Liu et al., 2000) where soft clays in shallow layers are known to have a higher subsidence potential (De Glopper and Ritzema, 1994). A smectite clay is derived from volcanic ash or tuff and has a high swelling potential, especially if consisting of montmorillonite (Liu et al., 2000;Bull, 1964;De Glopper and Ritzema, 1994). ...
... Clays are known to correlate with subsidence, depending on the amount, type, and moisture content of the clay (Bull, 1964;Liu et al., 2000) where soft clays in shallow layers are known to have a higher subsidence potential (De Glopper and Ritzema, 1994). A smectite clay is derived from volcanic ash or tuff and has a high swelling potential, especially if consisting of montmorillonite (Liu et al., 2000;Bull, 1964;De Glopper and Ritzema, 1994). The alluvial deposits in the Silver Bow alluvial basin are derived from Butte Quartz Monzonite (BQM), in which a common alteration will produce montmorillonite and other smectite clays (Zhang, 2000). ...
... This process occurs within the clay itself, where primary consolidation gradually releases excess pore-water and increases stress, while secondary compression relates to clay dehydration (Liu and Li, 2005;Liu et al., 2000). This dehydration process involves the release of interlayer water and can result in up to 36.3% volume reduction in smectitic clays (Liu et al., 2000). ...
Geophysical investigations, designed to characterize unique subsidence features of unknown natural origin, provide imaging analysis of potential causes of subsidence. Recent subsidence in the alluvial plain in Butte, Montana is unrelated to historic mining in the area. This study aims to utilize a combined application of shallow electrical resistivity imaging (ERI), self-potential (SP), and frequency-domain electromagnetic (FDEM) methods in order to develop a better understanding of the particular set of hydrogeological and environmental conditions that contribute to this unique phenomenon. Geophysical measurements provide lateral and vertical variations of electrical resistivity in the subsurface to a depth of 6 m while also contouring the streaming potential to help characterize the site-specific groundwater flow components. Least-squares inversion resistivity models and conductivity from electromagnetic data are compared to known well lithologic information to identify general variations of sediments with depth as well as delineate the extent of the known subsidence features. Site investigations indicate that the subsidence features in basin fill sediments are spatially associated with electrical and electromagnetic signatures of water seepage and sharp contacts between resistive and conductive sediment layers. ERI results showed a circular resistive anomaly in place of known subsidence locations and delineated lithologic heterogeneity in each site, suggesting a clay contact at shallow depth. The FDEM results complemented ERI and further characterized the depth and thickness of the clay. The SP results indicated surficial seepage associated with subsidence locations. A borehole was hand-augered. We did a sieve test, atterberg limits test, and ASD Terraspec Halo shortwave-infrared (SWIR) mineral analysis. The findings showed a fines ration from 36.1% to 38.1%, and clays are dominantly kaolinite PX, montmorillinite, and some ferryhydrite. This work sets a baseline site characterization and analysis on the origin of these subsidence features, where the subsidence is expected to be associated with volumetric changes in clay and porous media during surficial seepage.
... Clays are known to correlate with subsidence, depending on the amount, type, and moisture 537 content of the clay (Bull, 1964, Liu et al., 2000 where soft clays in shallow layers are known to have a 538 higher subsidence potential (de Glopper and Ritzema, 1994). A smectite clay is derived from volcanic ash 539 or tuff and has a high swelling potential, especially if consisting of montmorillonite (Liu et al., 2000, 540 Bull, 1964, de Glopper and Ritzema, 1994. ...
... Clays are known to correlate with subsidence, depending on the amount, type, and moisture 537 content of the clay (Bull, 1964, Liu et al., 2000 where soft clays in shallow layers are known to have a 538 higher subsidence potential (de Glopper and Ritzema, 1994). A smectite clay is derived from volcanic ash 539 or tuff and has a high swelling potential, especially if consisting of montmorillonite (Liu et al., 2000, 540 Bull, 1964, de Glopper and Ritzema, 1994. The alluvial deposits in the Silver Bow alluvial basin are 541 derived from Butte Quartz Monzonite (BQM), in which a common alteration will produce 542 montmorillonite and other smectite clays (Zhang, 2000). ...
... This contact is associated with the trend of anomalies 459 seen in the top three slices. 460 releases excess pore-water and increases stress, while secondary compression relates to clay dehydration 558 (Liu andLi, 2005, Liu et al, 2000). This dehydration process involves the release of interlayer water and 559 ...
Geophysical investigations, designed to characterize unique subsidence features of unknown natural origin, provide imaging analysis of potential causes of subsidence. Recent subsidence in the alluvial plain in Butte, Montana is unrelated to historic mining in the area. This study aims to utilize a combined application of shallow electrical resistivity tomography (ERT), self-potential (SP), and frequency-domain electromagnetic (FDEM) methods in order to develop a better understanding of the particular set of hydrogeological and environmental conditions that contribute to this unique phenomena. Geophysical measurements provide lateral and vertical variations of electrical resistivity in the subsurface to a depth of 10 m while also contouring the streaming potential in each site to help characterize the site-specific groundwater flow components. Least-square inversion resistivity models and conductivity from electromagnetic data are compared to known well lithologic information to identify general variations of sediments with depth as well as delineate the extent of the known subsidence features. Site investigations indicate that the subsidence features in basin fill sediments are spatially associated with electrical and electromagnetic signatures of water seepage and sharp contacts between resistive and conductive sediment layers. ERT results showed a circular resistive anomaly in place of known subsidence locations and delineated lithologic heterogeneity in each site, suggesting a clay contact at shallow depth. The FDEM results complemented ERT and further characterized the depth and thickness of the clay lens. The SP results indicated surficial seepage associated with subsidence locations. This work sets a baseline site characterization and analysis on the origin of these subsidence features, where the subsidence is expected to be associated with volumetric changes in clay and porous media during surficial seepage.
... Clays are known to correlate with subsidence, depending on the amount, type, and moisture content of the clay (Bull, 1964;Liu et al., 2000) where soft clays in shallow layers are known to have a higher subsidence potential (De Glopper and Ritzema, 1994). A smectite clay is derived from volcanic ash or tuff and has a high swelling potential, especially if consisting of montmorillonite (Liu et al., 2000;Bull, 1964;De Glopper and Ritzema, 1994). ...
... Clays are known to correlate with subsidence, depending on the amount, type, and moisture content of the clay (Bull, 1964;Liu et al., 2000) where soft clays in shallow layers are known to have a higher subsidence potential (De Glopper and Ritzema, 1994). A smectite clay is derived from volcanic ash or tuff and has a high swelling potential, especially if consisting of montmorillonite (Liu et al., 2000;Bull, 1964;De Glopper and Ritzema, 1994). The alluvial deposits in the Silver Bow alluvial basin are derived from Butte Quartz Monzonite (BQM), in which a common alteration will produce montmorillonite and other smectite clays (Zhang, 2000). ...
... This process occurs within the clay itself, where primary consolidation gradually releases excess pore-water and increases stress, while secondary compression relates to clay dehydration (Liu and Li, 2005;Liu et al., 2000). This dehydration process involves the release of interlayer water and can result in up to 36.3% volume reduction in smectitic clays (Liu et al., 2000). ...
Interest in finding the causes of reoccurring late summer dewatering of Lolo Creek, Montana, led to geophysical and hydrogeologic studies to understand the cause and effect relationship between surface water uses, groundwater uses and stream flow, critical to water management decisions. Electrical Resistivity Tomography (ERT), Spontaneous Potential (SP), Multichannel Analysis of Surface Waves (MASW) and Seismic Refraction Tomography methods were used to provide information on potential seepage pathways leading to dewatering of Lolo Creek and the subsurface lithology of the area. Results from the MASW and seismic refraction tomography studies showed the bedrock at depths of about 35 m close to Highway 93 and 27 m at the end of the 288 m East-West seismic line running through Lewis and Clark Drive. ERT results showed a shallow, high- resistive layer underlain by low resistive layers. The Eocene bedrock (mylonite) was found to have a resistivity between 180 and 400 Ωm. A geologic fault was inferred in a 360 m East-West ERT profile. SP measurements around the inferred fault indicate a zone of infiltration, with SP values between −18 mV to −2 mV. A 1D-depth velocity profile obtained from MASW survey located close to East-West ERT profile, indicates a low velocity subsurface between 0 and 39 m, which is interpreted to be fractured bedrock. This fractured, shallow bedrock and associated fault work as a seepage path from the shallow to deep aquifer and could possibly account for dewatering of the Creek during low-flow periods in the late summer.
