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It is a critical concern to properly manage the risks associated with the stability of tailings and dredge sludge dams. This requires the knowledge of the pore water pressure (PWP) within a slurried material during and after the deposition. The evaluation of the PWP can also help to estimate the settlement, which is important for the water management and design of the storage facility. An analytical solution based on the Gibson model has been proposed by the authors to evaluate the excess PWP during the slurry deposition. However, there is no solution available to estimate the excess PWP and volume of draining water after the end of slurry deposition. In this paper, a new solution is proposed to evaluate the PWP, settlement, and volume of draining water after the slurry deposition on a pervious base. The proposed PWP solution is partly validated by numerical modeling with SIGMA/W and laboratory results. The influence of the consolidation coefficient and filling rate on the distribution and evolution of PWP is analyzed. The solution development for estimating the excess PWP, volume of draining water and settlement after slurry deposition on an impervious base has been presented in a companion paper (part I). [ABSTRACT FROM AUTHOR]

In coastal engineering, the storage of dredged sludge needs the construction of containment structures. In mining engineering, the surface disposal of tailings slurry requires the construction of tailings dam. In both cases, one needs to estimate the excess pore water pressure (PWP), draining water and settlement of the slurry during and after the deposition. An analytical solution presented by the authors based on a model proposed by Gibson in 1958 can be used to evaluate the excess PWP during slurry deposition. The equation given by Gibson in 1958 for assessing the excess PWP after the end of slurry deposition cannot be used because it contains an error. In addition, there is no existing solution to estimate the settlement and volume of draining water after the end of slurry deposition. In this paper, a new solution based on the Gibson's governing equation is proposed to evaluate the excess PWP, settlement and volume of draining water after the end of slurry deposition on an impervious base. The proposed solution is partly validated by numerical and laboratory test results. The solution for estimating the excess PWP, settlement and volume of draining water after the end of slurry deposition on a pervious base is presented in a companion paper. [ABSTRACT FROM AUTHOR]

This paper presents a methodology to link the ground surface displacements to a tunnel boring machine (TBM) operation parameters. The approach consists at first in the exploration and description of the TBM operation parameters, recorded during the construction of the Toulouse (France) subway line B tunnel, using principal component analysis and agglomerative hierarchical clustering (AHC). Then, partial least squares (PLS) regression models were developed for the prediction of the displacements for the two groups of observations, identified by the AHC (pure settlements and heave at the center), as a function of the ten selected TBM operation parameters and the geometry parameter ( X/ H). The developed models take into account the nonlinear relationship between displacements and the operation parameters and the collinearity that exists in the parameters. In addition, the PLS regression allows identifying the parameters that affect the displacement of each group. The comparison of the predicted displacements with the measurements for the validation samples of the two groups shows good agreement. [ABSTRACT FROM AUTHOR]

Research on the seepage deformation of saturated soft soil has resulted in many achievements based, mainly, on existing seepage-deformation control equations. In reality, however, these control equations and related parameters suffer from many problems. The conductivity coefficient in the seepage control equation and the consolidation coefficient in the consolidation equation clearly resemble each other in form. However, in existing regulations and practice, soil deformation is rarely calculated by substituting the conductivity coefficient obtained from field hydrogeological experiments for the consolidation coefficient. Similarly, seepage is seldom calculated by substituting the conductivity coefficient with the consolidation coefficient obtained from consolidation experiments. This can be attributed to the fact that the two coefficients have some obvious differences. Moreover, the settlement deformation of soil calculated using the existing seepage and consolidation models does not agree very well with the measured deformation. Also, the values calculated using different models usually deviate markedly. Research indicates that these problems derive from the fact that the seepage and consolidation equations are based on different concepts of elementary volume. This study proposes using two separate elementary volume concepts: deformation elementary volume and control elementary volume. The concepts are adopted for saturated soft soil and the results used to analyze the relationships and differences between the two concepts. Moreover, we developed a conceptual data model (CDM) for the water released from and the deformation of the saturated soil. The model discloses the differences between the consolidation and conductivity coefficients both in their physical significances and magnitudes. The inter-relationship between the two coefficients is also revealed. An analytical solution for the deformation and water released from saturated soft soil is deduced based on the CDM model and the relationship between the hydrogeological and consolidation deformation parameters is established. A physical test model for saturated soft soil under certain conditions is also designed to verify the analytical solution using a method of curve fitting. Seepage and deformation tests and case studies show that the parameters calculated using the consolidation model are in agreement with those obtained from the CDM seepage model based on the measured data for flux and settlement vs. time. Furthermore, the relationship between conductivity and consolidation coefficients is verified. The method suggested in this paper is generally applicable to problems involving the consolidation coefficient, volume compressibility, conductivity coefficient, hydraulic conductivity, and specific storage of saturated soft soil, etc. Thus, its potential applications are numerous. [ABSTRACT FROM AUTHOR]

This paper presents the research carried out to shed light on a sudden settlement and its consequences that occurred in the city of Oviedo. Ground subsidence in the Ventanielles area led to severe damage and the subsequent demolition of two buildings with 362 flats, resulting in losses of 18 million euros. The investigation allowed the identification of a buried sinkhole, filled with up to 13 m of fluvial sediments, linked to the dissolution of a Paleogene gypsum unit with a maximum thickness of 18 m and containing metre-sized cavities. The triggering process that reactivated the paleosinkhole was found to be the pumping of water from a confined aquifer, related to excavation work during the construction of a nearby underground parking lot; this extraction modified the natural hydrological regime. The compaction and migration of alluvial sand towards the karstic cavities were the main subsidence mechanisms responsible for the structural damage, aggravated by the poor quality of the buildings and the geotechnical behaviour of the supporting ground. [ABSTRACT FROM AUTHOR]

This paper investigates the fundamental characteristics of shear strength and deformation of crushed oyster shell–sand mixtures to stimulate recycling of waste oyster shells. Standard penetration tests (SPT) and large-scale direct-shear tests were carried out with different kinds of dry unit weight and mixing rate of oyster shell–sand mixture. Correlations between N-value, dry unit weight, and friction angle of mixtures were observed from the results of experimental tests, making it possible to estimate the in situ strength from SPT, and the coefficient of volume compressibility from the confined direct-shear compression test. These results also make it possible to compute the settlement of oyster shell–sand mixture when used in soft ground improvement. [ABSTRACT FROM AUTHOR]

The settlement of an embankment body is always a significant technological issue in highway and railway construction. The embankment body is usually constructed using unsaturated soil, whose deformation consists of three parts, instantaneous deformation, primary-consolidation deformation and secondary-consolidation deformation. The primary consolidation and the secondary compression deformations are not two separate processes, but they influence each other, that are the deformation of the embankment body is the coupling-effect result of unsaturated-rheology and consolidation. Based on the results of uniaxial compression creep test of crushed Red-layers mudstone soils and the principle of the single stress state variable in unsaturated soils, the theory of unsaturated embankment settlement of Red-layers is put forward. Physical centrifugal tests and numerical simulation of centrifugal loading process are adapted not only to study the relationships of the settlement of the embankment body filled with different compaction coefficients versus embankment filling height, as well as the settlement after construction versus time, but also to predict the settlement after construction. Based on these studies, a project case, the settlement characteristics of a section of the railway line for passenger traffic from Chongqing to Suining have been studied by numerical simulation considering actual filling process. These show that the physical centrifugal tests and site monitoring data largely coincide with the corresponding numerical simulation results, showing the high validation of the proposed coupling-theory. [ABSTRACT FROM AUTHOR]

Leachate recirculation (LR) was pioneered in the USA in the 1970s as a means to enhance the degradation of landfill wastes, degrade or immobilize harmful compounds within the waste mass, and store excess leachate. LR offers many economic and environmental benefits to municipal solid waste (MSW) landfills. The main objective of this study was to investigate the migration law of LR and develop design guidelines for leachate recirculation systems consisting of spray irrigation when considering the stratification of MSW permeability. A bioreactor landfill will experience more rapid and complete settlement than a traditional landfill, which is mostly attributed to the weight of MSW. The waste at each layer in the landfill experiences a different pressure depending on the depth, which leads to vertical gradients in the void ratio and permeability coefficients of the waste in the landfill. To study LR in bioreactor landfills when considering the stratification of the MSW permeability, a new model was developed based on the law of conservation of mass, the modified Darcy's law, and Stoltz's settlement model. Using this model, the transport law of injected leachate into bioreactor landfills was determined under unsaturated conditions. The effects of various parameters (e.g., permeability stratification, compaction degree, initial void ratio, and injection intensity) on the water content of MSW and unit surface area recirculation were analyzed. [ABSTRACT FROM AUTHOR]

During the construction of twin tunnels excavated in close proximity to each other, the prediction of the influence of a new tunnel construction on an already existing one plays an important role in the design and construction of the tunnels. The researches in the literature indicate that this influence depends to a great extent on the distance between the tunnels. However, most of the reported cases in the literature on the mechanized excavation of twin tunnels have focused on the effects of the relative position between the two tunnels on surface settlements. Some of them have dealt with the behaviour of the tunnel structure through the use of simplified numerical models. The numerical investigation performed in this study, using the FLAC finite difference code, has made it possible to predict the impact between tunnels using full three-dimensional simulations, in which most of the elements of a mechanized tunnel process have been modelled. The effects of tunnel distance on the structural forces induced in both tunnels, and the displacements in the surrounding ground have been highlighted. A modification has been made to the superposition method to predict the settlement surface trough over twin tunnels. [ABSTRACT FROM AUTHOR]

During leachate recirculation, a bioreactor landfill will experience more rapid and complete settlement, which is mainly attributed to the weight of municipal solid waste (MSW) and its biodegradation. The settlement of MSW may cause the decrease of void ratio of MSW, which will influence the permeability of MSW and the leachate quantity that can be held in bioreactor landfills. In this study, a new one-dimensional model of leachate recirculation using infiltration pond is developed. The new method is not only capable of describing leachate flow considering the effect of MSW settlement, but also accounting separately leachate flow in saturated and unsaturated zones. Moreover, the effects of operating parameters are evaluated with a parametric study. The analyzing results show that the influence depth of leachate recirculation considering the effect of MSW settlement is smaller than the value without considering the effect. The influence depth and leachate recirculation volume increase with the increase of infiltration pond pressure head and MSW void ratio. This indicates that the field compaction of MSW has a great influence on the leachate recirculation. [ABSTRACT FROM AUTHOR]

Subsidence related to multiple natural and human-induced processes affects an increasing number of areas worldwide. Although this phenomenon may involve surface deformation with 3D displacement components, negative vertical movement, either progressive or episodic, tends to dominate. Over the last decades, differential SAR interferometry (DInSAR) has become a very useful remote sensing tool for accurately measuring the spatial and temporal evolution of surface displacements over broad areas. This work discusses the main advantages and limitations of addressing active subsidence phenomena by means of DInSAR techniques from an end-user point of view. Special attention is paid to the spatial and temporal resolution, the precision of the measurements, and the usefulness of the data. The presented analysis is focused on DInSAR results exploitation of various ground subsidence phenomena (groundwater withdrawal, soil compaction, mining subsidence, evaporite dissolution subsidence, and volcanic deformation) with different displacement patterns in a selection of subsidence areas in Spain. Finally, a cost comparative study is performed for the different techniques applied. [ABSTRACT FROM AUTHOR]

The behavior of the Gimpo #2 landfill, which is an active landfill and the largest in Korea, is analyzed using field measurement data obtained from various field instruments installed within the landfill. The data included in this analysis are the leachate head within the landfill, waste load data using soil pressure plate and settlement data from settlement plate on the surface of the waste of each stage fill including the settlement of the soft foundation clay soil. Landfill blocks are selected both near the embankment and in the center area of the landfill. The analysis of the field-monitored data showed that the leachate head increase was negligible near the embankment. It was significant in the central block as the waste loads increase and reached 15 m at the fourth stage of waste disposal. The reason that the leachate head is higher in the central block than near the embankment is due to the long drainage path and the loss of gradient of drain pipes. The range of unit weight of the waste converted from the measurement data of earth pressure cell was 0.91-1.24 t/m and the average value was 1.05 t/m. The values reflect well the waste compositions recently buried in GML #2, since from 1998 the waste disposed in GML #2 did not contain food waste. The magnitude of final settlements that occurred in each stage loading of 5 m thickness in the peripheral block was very close to 120 cm. The settlement rate of the waste by dividing the thickness of waste was 24 %. This rate can be divided into 10 % by waste loading and 14 % by waste decomposition. The delay of settlements is recognized in each waste layer for second and third loading in the central block due to the accumulation of leachate within the landfill. [ABSTRACT FROM AUTHOR]

A good prediction of solid waste landfill settlement is important for landfill design and rehabilitation. A one-dimensional model which accounts for mechanical settlement and biodegradation processes is developed to simulate the settlement behavior of municipal solid waste landfill. The derivation of analytical solutions for specific conditions is introduced. The numerical approach, capable of coping with more general conditions, is also presented to estimate the spatial and temporal distribution of landfill settlement. The proposed model can simulate typical features of short- and long-term landfill settlement behaviors. With proper selection of parameter values, field measurements are well simulated by this model. The effects of some design parameters on the settlement behavior of municipal solid waste landfills are also examined with the help of this model. [ABSTRACT FROM AUTHOR]

Annual variation in the amount and composition of waste deposited in the Gimpo #2 landfill, the largest landfill around Seoul, Korea, is reviewed, and the stability of the same landfill is analyzed during waste disposal. For the stability analysis, three empirical stability prediction methods, i.e., linear stability, displacement velocity, and curve stability methods, are used to analyze field-measured settlement and horizontal displacement data. The analysis indicated that national waste management policy has greatly influenced the annual variation in the amount and composition of waste deposited in the landfill. Continuous measurement of geotechnical data and the use of stability analysis based on these data are necessary for landfills on seashore clay foundation. Stability of the landfill must be examined with various methods to ensure accurate determination of its stability. [ABSTRACT FROM AUTHOR]