Landslides associated with hillside cuttings in igneous rock saprolites are a serious natural haz... more Landslides associated with hillside cuttings in igneous rock saprolites are a serious natural hazard in Hong Kong and have been extensively studied by government agencies and local universities for many years from the perspective of soil and rock engineering. A review of the case studies for some major landslides, especially deep-seated landslides, shows certain puzzling features. First, a number of failed slopes had failed again after they were cut back to a gentler angle designed to be safe based on theoretical calculations. Second, some of the failures were postulated to have been caused by the occurrence of a high groundwater table after rainfall, but weepholes in some slopes were dry and piezometers did not show much response to the rainfall.
Despite prevailing dry conditions, groundwater-fed lakes are found among the earth&am... more Despite prevailing dry conditions, groundwater-fed lakes are found among the earth's tallest sand dunes in the Badain Jaran Desert, China. Indirect evidence suggests that some lakes are shrinking. However, relatively few studies have been carried out to assess the regional groundwater conditions and the fate of the lakes due to the remoteness and severity of the desert environment. Here we use satellite information to demonstrate an ongoing slow decrease in both lake level and groundwater storage. Specifically, we use Ice, Cloud, and land Elevation Satellite altimetry data to quantify water levels of the lakes and show overall decreases from 2003 to 2009. We also use water storage changes from the Gravity Recovery and Climate Experiment and simulated soil and water changes from the Global Land Data Assimilation System to demonstrate long-term groundwater depletion in the desert. Rainfall increase driven by climate change has increased soil water and groundwater storage to a certain degree but not enough to compensate for the long-term decline. If countermeasures are not taken to control the pumping, many lakes will continue to shrink, causing an ecological and environmental disaster in the fragile desert oases.
Wells played an important role in early human settlements and are an important indicator of civil... more Wells played an important role in early human settlements and are an important indicator of civilization. After the invention of wells, primitive societies could use groundwater to serve human purposes and were no longer confined to areas with convenient surface water (Jiao, 2007). Awell was usually a gathering place of a village or town. In fact, the word marketplace or Shi jing in ancient Chinese literature literally means market and well. The market originated from a well site because people got together at wells to draw water while selling their goods (Du & Koenig, 2012).
The soil water retention curve is a fundamental characteristic of unsaturated zone flow and trans... more The soil water retention curve is a fundamental characteristic of unsaturated zone flow and transport properties. Recent studies show that an air-entry value is needed in a soil water retention equation in order to provide a better prediction of relative hydraulic conductivity. A new equation considering the air-entry value is proposed to describe the soil water retention curve. The performance of the proposed equation is contrasted with a well-supported equation by comparing measured and calculated data for 14 soils, representing various soil textures, which range from sandstone to clay. Results show that the proposed equation provides adequate characterization of the soil water retention curves. The equation for predicting relative hydraulic conductivity is derived from the proposed soil water retention equation. An empirical equation for relative hydraulic conductivity is also used. Our results show that the agreement between the predicted and measured relative hydraulic conducti...
ABSTRACT Permeability, which generally decreases with depth, is the most important parameter that... more ABSTRACT Permeability, which generally decreases with depth, is the most important parameter that controls fluid flow in Earth's crust. There are two categories of models that describe the permeability-depth relationship: one category forces permeability to approach infinity at the surface, and the other category leads to too much decrease in permeability with depth. Here, we present a new model that integrates and reconciles existing models thus allowing for complete description of crustal permeability from the surface and through the entire crust. Our model provides improved description of observed data and is applicable to both continental crust and oceanic crust. It can be used to obtain a better understanding of the role of fluids in crustal processes.
We follow the morphology of the interface between polystyrene (PS) and poly(styrene-r-maleic anhy... more We follow the morphology of the interface between polystyrene (PS) and poly(styrene-r-maleic anhydride) (PSMA) at various normalized interfacial excesses z^*/Rg of graft copolymer formed by reaction between deuterated PS terminated with a benzyl amine group (dPS-NH_2) and (PSMA). For dPS-NH2 chains with polymerization indices N=250, 55 and 33, we find from forward recoil spectrometry that z^*/Rg values as large as
1] Relative permeability of the nonwetting phase in a multiphase flow in porous media is a functi... more 1] Relative permeability of the nonwetting phase in a multiphase flow in porous media is a function of phase saturation. Specific expressions of this function are commonly determined by combining soil water retention curves with relative nonwetting phase permeability models. Experimental evidence suggests that the relative permeability of the nonwetting phase can be significantly overestimated by the existing relative permeability models. A new model for the prediction of relative nonwetting phase permeability from soil water retention curves is proposed in this paper. A closed form expression can be obtained in combination with soil water retention curves. The model is mathematically simple and can easily and efficiently be implemented in numerical models of multiphase flow processes in porous media. The predicting capability of the proposed model is contrasted with wellsupported models by comparing the measured and predicted relative air permeability data for 11 soils, representing a wide range of soil textures, from sand to silty clay loam. In most of the cases the proposed model improves the agreement between the predicted relative air permeability and the measured data.
International Journal for Numerical and Analytical Methods in Geomechanics, 2004
The soil around a drain well is traditionally divided into smeared zone and undisturbed zone with... more The soil around a drain well is traditionally divided into smeared zone and undisturbed zone with constant hydraulic conductivity. In reality, hydraulic conductivity of the soil changes continuously and it may not be always appropriate to approximate its distribution with two zones. In this study, the horizontal hydraulic conductivity of the soil is described by an arbitrary function of radial distance. The horizontal flow under equal strain condition is analysed for a soil-drain system with a circular or regular polygonal boundary. It is found that the horizontal flow can be generally characterized with a linear equation in which the flow rate of water through soil-drain interface is proportional to the difference between the average excess pore pressure in the soil and the excess pore pressure in the drain well. The water exchange between the drain and the soil is analogous to that between fractures and matrix in a double porosity system, a popular conceptual model of fracture rocks. On the basis of this characterization, a simplified approach to analyse soil-drain systems is developed with one-dimensional double porosity model (DPM). Analytical solutions for both fully and partially penetrating drains are derived. The solution for partially penetrating drains is compared with both numerical and approximate analytical results in literature.
An approach for better understanding of the physical implication of estimated aquifer parameters ... more An approach for better understanding of the physical implication of estimated aquifer parameters is demonstrated by analysing the pumping test data at Cottam in the Nottingham aquifer, UK. A sensitivity analysis showed that the area represented by the estimated parameters was much smaller than the area covered by the depression cone. After parameters are estimated, further research should be carried out to understand what portions of the aquifer the parameters represent. The parameters estimated at Cottam represented mainly aquifer features between roughly 100 and 2000 m. The sensitivity analysis also showed that the observed drawdown being satisfactorily matched by a model with uniform parameters does not prove that the aquifer is homogeneous. Slightly anomalous data may imply the existence of large anomalous zones. Although the drawdowns at Cottam could be 'satisfactorily' fitted by a model with uniform parameters, the fit could be improved by a model using a more permeable aquifer but with a zone about 700 m wide and with 42% less transmissivity.
Surface water and groundwater in the Heihe river basin of China are interconnected and the patter... more Surface water and groundwater in the Heihe river basin of China are interconnected and the pattern of water resources exploitation has a direct effect on the interaction of groundwater and surface water, especially on a downstream oasis. A threedimensional groundwater flow simulation model with eight model layers was established to simulate the regional groundwater flow in the multilayered aquifer system and the interaction among the rivers, springs, and groundwater. The model was calibrated not only with historical water levels but also with the investigated baseflow and spring flux. The simulation results of the numerical model match reasonably well with the observed groundwater levels, baseflow to rivers, and spring flux. The numerical simulation also demonstrates that the hydraulic connection between the river and the aquifers has transferred from the coupling to decoupling at some reaches. It is suggested that there is a vital need to reduce groundwater withdrawal and to rationalize the use of both groundwater and surface water in order to maintain sustainable development in the study area.
Springs and seeps occur in the spaces around Po Hing Fong Street in the Mid-Levels area, Hong Kon... more Springs and seeps occur in the spaces around Po Hing Fong Street in the Mid-Levels area, Hong Kong. Most of the springs occur through the drainage weepholes on retaining walls at the street. This paper first examines the geology and history of the springs. The paper then reports the findings from a 1-year comprehensive spring monitoring programme. The temporal variations of flow rate, physiochemical parameters and hydrochemistry of the springs are discussed. The average temperatures of the springs were close to the mean air temperature, although there was a systematic lag time of 40 to 50 days between the peak air temperature and highest water temperatures. Spring waters from two rows of weepholes in the retaining wall showed significantly different physical and hydrochemical responses to the changes in rainfall and temperature, though their vertical distance is only about 1 m. The results suggest that water from the upper row of weepholes may represent a recharge source that is shallow or close to the spring outlets, whereas that from the lower row of weepholes may represent a recharge source that is much deeper or further up the hill. Although the spring flows increased rapidly after rainstorms, analysis of the total dissolved solids showed a delayed response to rainstorm events. The concentration of individual ions in the spring water varied in a unique way in response to rainstorm events. It is clear that the presence of underground man-made drainage systems and the leakage from water mains in the study area may add complexity to the solute responses and transport mechanisms. Further studies are required to constrain the impacts of these man-made structures on the hydrogeology of the springs.
In 1973, traces of China’s early Neolithic Hemudu culture (7,000–5,000 BP) were discovered in the... more In 1973, traces of China’s early Neolithic Hemudu culture (7,000–5,000 BP) were discovered in the village of Hemudu in Yuyao County, Zhejiang Province, in the lower Yangtze River coastal plain. The site has yielded animal and plant remains in large quantities and large numbers of logs secured with tenon and mortise joints, commonly used in wooden buildings and other wooden structures.
Many coastal areas have been intensively urbanized because people living and working on or near c... more Many coastal areas have been intensively urbanized because people living and working on or near coastlines are increasing. Land reclamation from the sea and high-rise buildings are common approaches to satisfying the growing needs for more housing and other land use. Coastal areas are usually the ultimate discharge zones of groundwater systems. Using a coastal area in Hong Kong as a case study, this paper discusses the change in a terrenos recuperados del mar, como las cimentaciones profundas a lo largo de la línea de costa, han contribuido a la modificación del sistema de flujo, pero las cimentaciones profundas han causado el mayor impacto, especialmente cuando se presenta una zona de alta conductividad en la parte mµs elevada del µrea.
Landslides associated with hillside cuttings in igneous rock saprolites are a serious natural haz... more Landslides associated with hillside cuttings in igneous rock saprolites are a serious natural hazard in Hong Kong and have been extensively studied by government agencies and local universities for many years from the perspective of soil and rock engineering. A review of the case studies for some major landslides, especially deep-seated landslides, shows certain puzzling features. First, a number of failed slopes had failed again after they were cut back to a gentler angle designed to be safe based on theoretical calculations. Second, some of the failures were postulated to have been caused by the occurrence of a high groundwater table after rainfall, but weepholes in some slopes were dry and piezometers did not show much response to the rainfall.
Despite prevailing dry conditions, groundwater-fed lakes are found among the earth&am... more Despite prevailing dry conditions, groundwater-fed lakes are found among the earth's tallest sand dunes in the Badain Jaran Desert, China. Indirect evidence suggests that some lakes are shrinking. However, relatively few studies have been carried out to assess the regional groundwater conditions and the fate of the lakes due to the remoteness and severity of the desert environment. Here we use satellite information to demonstrate an ongoing slow decrease in both lake level and groundwater storage. Specifically, we use Ice, Cloud, and land Elevation Satellite altimetry data to quantify water levels of the lakes and show overall decreases from 2003 to 2009. We also use water storage changes from the Gravity Recovery and Climate Experiment and simulated soil and water changes from the Global Land Data Assimilation System to demonstrate long-term groundwater depletion in the desert. Rainfall increase driven by climate change has increased soil water and groundwater storage to a certain degree but not enough to compensate for the long-term decline. If countermeasures are not taken to control the pumping, many lakes will continue to shrink, causing an ecological and environmental disaster in the fragile desert oases.
Wells played an important role in early human settlements and are an important indicator of civil... more Wells played an important role in early human settlements and are an important indicator of civilization. After the invention of wells, primitive societies could use groundwater to serve human purposes and were no longer confined to areas with convenient surface water (Jiao, 2007). Awell was usually a gathering place of a village or town. In fact, the word marketplace or Shi jing in ancient Chinese literature literally means market and well. The market originated from a well site because people got together at wells to draw water while selling their goods (Du & Koenig, 2012).
The soil water retention curve is a fundamental characteristic of unsaturated zone flow and trans... more The soil water retention curve is a fundamental characteristic of unsaturated zone flow and transport properties. Recent studies show that an air-entry value is needed in a soil water retention equation in order to provide a better prediction of relative hydraulic conductivity. A new equation considering the air-entry value is proposed to describe the soil water retention curve. The performance of the proposed equation is contrasted with a well-supported equation by comparing measured and calculated data for 14 soils, representing various soil textures, which range from sandstone to clay. Results show that the proposed equation provides adequate characterization of the soil water retention curves. The equation for predicting relative hydraulic conductivity is derived from the proposed soil water retention equation. An empirical equation for relative hydraulic conductivity is also used. Our results show that the agreement between the predicted and measured relative hydraulic conducti...
ABSTRACT Permeability, which generally decreases with depth, is the most important parameter that... more ABSTRACT Permeability, which generally decreases with depth, is the most important parameter that controls fluid flow in Earth's crust. There are two categories of models that describe the permeability-depth relationship: one category forces permeability to approach infinity at the surface, and the other category leads to too much decrease in permeability with depth. Here, we present a new model that integrates and reconciles existing models thus allowing for complete description of crustal permeability from the surface and through the entire crust. Our model provides improved description of observed data and is applicable to both continental crust and oceanic crust. It can be used to obtain a better understanding of the role of fluids in crustal processes.
We follow the morphology of the interface between polystyrene (PS) and poly(styrene-r-maleic anhy... more We follow the morphology of the interface between polystyrene (PS) and poly(styrene-r-maleic anhydride) (PSMA) at various normalized interfacial excesses z^*/Rg of graft copolymer formed by reaction between deuterated PS terminated with a benzyl amine group (dPS-NH_2) and (PSMA). For dPS-NH2 chains with polymerization indices N=250, 55 and 33, we find from forward recoil spectrometry that z^*/Rg values as large as
1] Relative permeability of the nonwetting phase in a multiphase flow in porous media is a functi... more 1] Relative permeability of the nonwetting phase in a multiphase flow in porous media is a function of phase saturation. Specific expressions of this function are commonly determined by combining soil water retention curves with relative nonwetting phase permeability models. Experimental evidence suggests that the relative permeability of the nonwetting phase can be significantly overestimated by the existing relative permeability models. A new model for the prediction of relative nonwetting phase permeability from soil water retention curves is proposed in this paper. A closed form expression can be obtained in combination with soil water retention curves. The model is mathematically simple and can easily and efficiently be implemented in numerical models of multiphase flow processes in porous media. The predicting capability of the proposed model is contrasted with wellsupported models by comparing the measured and predicted relative air permeability data for 11 soils, representing a wide range of soil textures, from sand to silty clay loam. In most of the cases the proposed model improves the agreement between the predicted relative air permeability and the measured data.
International Journal for Numerical and Analytical Methods in Geomechanics, 2004
The soil around a drain well is traditionally divided into smeared zone and undisturbed zone with... more The soil around a drain well is traditionally divided into smeared zone and undisturbed zone with constant hydraulic conductivity. In reality, hydraulic conductivity of the soil changes continuously and it may not be always appropriate to approximate its distribution with two zones. In this study, the horizontal hydraulic conductivity of the soil is described by an arbitrary function of radial distance. The horizontal flow under equal strain condition is analysed for a soil-drain system with a circular or regular polygonal boundary. It is found that the horizontal flow can be generally characterized with a linear equation in which the flow rate of water through soil-drain interface is proportional to the difference between the average excess pore pressure in the soil and the excess pore pressure in the drain well. The water exchange between the drain and the soil is analogous to that between fractures and matrix in a double porosity system, a popular conceptual model of fracture rocks. On the basis of this characterization, a simplified approach to analyse soil-drain systems is developed with one-dimensional double porosity model (DPM). Analytical solutions for both fully and partially penetrating drains are derived. The solution for partially penetrating drains is compared with both numerical and approximate analytical results in literature.
An approach for better understanding of the physical implication of estimated aquifer parameters ... more An approach for better understanding of the physical implication of estimated aquifer parameters is demonstrated by analysing the pumping test data at Cottam in the Nottingham aquifer, UK. A sensitivity analysis showed that the area represented by the estimated parameters was much smaller than the area covered by the depression cone. After parameters are estimated, further research should be carried out to understand what portions of the aquifer the parameters represent. The parameters estimated at Cottam represented mainly aquifer features between roughly 100 and 2000 m. The sensitivity analysis also showed that the observed drawdown being satisfactorily matched by a model with uniform parameters does not prove that the aquifer is homogeneous. Slightly anomalous data may imply the existence of large anomalous zones. Although the drawdowns at Cottam could be 'satisfactorily' fitted by a model with uniform parameters, the fit could be improved by a model using a more permeable aquifer but with a zone about 700 m wide and with 42% less transmissivity.
Surface water and groundwater in the Heihe river basin of China are interconnected and the patter... more Surface water and groundwater in the Heihe river basin of China are interconnected and the pattern of water resources exploitation has a direct effect on the interaction of groundwater and surface water, especially on a downstream oasis. A threedimensional groundwater flow simulation model with eight model layers was established to simulate the regional groundwater flow in the multilayered aquifer system and the interaction among the rivers, springs, and groundwater. The model was calibrated not only with historical water levels but also with the investigated baseflow and spring flux. The simulation results of the numerical model match reasonably well with the observed groundwater levels, baseflow to rivers, and spring flux. The numerical simulation also demonstrates that the hydraulic connection between the river and the aquifers has transferred from the coupling to decoupling at some reaches. It is suggested that there is a vital need to reduce groundwater withdrawal and to rationalize the use of both groundwater and surface water in order to maintain sustainable development in the study area.
Springs and seeps occur in the spaces around Po Hing Fong Street in the Mid-Levels area, Hong Kon... more Springs and seeps occur in the spaces around Po Hing Fong Street in the Mid-Levels area, Hong Kong. Most of the springs occur through the drainage weepholes on retaining walls at the street. This paper first examines the geology and history of the springs. The paper then reports the findings from a 1-year comprehensive spring monitoring programme. The temporal variations of flow rate, physiochemical parameters and hydrochemistry of the springs are discussed. The average temperatures of the springs were close to the mean air temperature, although there was a systematic lag time of 40 to 50 days between the peak air temperature and highest water temperatures. Spring waters from two rows of weepholes in the retaining wall showed significantly different physical and hydrochemical responses to the changes in rainfall and temperature, though their vertical distance is only about 1 m. The results suggest that water from the upper row of weepholes may represent a recharge source that is shallow or close to the spring outlets, whereas that from the lower row of weepholes may represent a recharge source that is much deeper or further up the hill. Although the spring flows increased rapidly after rainstorms, analysis of the total dissolved solids showed a delayed response to rainstorm events. The concentration of individual ions in the spring water varied in a unique way in response to rainstorm events. It is clear that the presence of underground man-made drainage systems and the leakage from water mains in the study area may add complexity to the solute responses and transport mechanisms. Further studies are required to constrain the impacts of these man-made structures on the hydrogeology of the springs.
In 1973, traces of China’s early Neolithic Hemudu culture (7,000–5,000 BP) were discovered in the... more In 1973, traces of China’s early Neolithic Hemudu culture (7,000–5,000 BP) were discovered in the village of Hemudu in Yuyao County, Zhejiang Province, in the lower Yangtze River coastal plain. The site has yielded animal and plant remains in large quantities and large numbers of logs secured with tenon and mortise joints, commonly used in wooden buildings and other wooden structures.
Many coastal areas have been intensively urbanized because people living and working on or near c... more Many coastal areas have been intensively urbanized because people living and working on or near coastlines are increasing. Land reclamation from the sea and high-rise buildings are common approaches to satisfying the growing needs for more housing and other land use. Coastal areas are usually the ultimate discharge zones of groundwater systems. Using a coastal area in Hong Kong as a case study, this paper discusses the change in a terrenos recuperados del mar, como las cimentaciones profundas a lo largo de la línea de costa, han contribuido a la modificación del sistema de flujo, pero las cimentaciones profundas han causado el mayor impacto, especialmente cuando se presenta una zona de alta conductividad en la parte mµs elevada del µrea.
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