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Introduction: Many theories of consolidation for soils have been proposed in the past, but most of them have ignored the structural characteristics of clay, yet the natural layered soils are widely distributed around the world. Methods: A theoretical model is established to analyze the one-dimensional consolidation behavior of layered soils, in which a time-dependent drainage boundary and the structural characteristics of the soil are taken into account. Using the integral transform and characteristic function methods, the analytical solution is derived, the effectiveness of which is evaluated against the degradation of solutions and the numerical results calculated using the finite element method. Results and discussion: Finally, the influences of interface parameter, soil permeability coefficient and soil compressibility on consolidation behaviors are discussed. Results show that in structured soils, early dissipation of excess pore water pressure and consolidation rates are predominantly influenced by interface parameters, permeability, and volume compression coefficients. Higher values of these parameters accelerate early stages of consolidation, which is especially evident in the upper soil layers. Over time, the distinct effects of interface and permeability coefficients on consolidation diminish. Higher volume compression coefficients, while initially beneficial, eventually slow down the consolidation process, indicating an interaction with the ongoing soil structural changes. [ABSTRACT FROM AUTHOR]

ABSTRACT Prefabricated horizontal drains combined with vacuum preloading (PHDs‐VP) have addressed the shortcomings of prefabricated vertical drains combined with vacuum preloading (PVDs‐VP), beginning to emerge as a popular method for dredged slurry treatment. However, theoretical research on PHDs‐VP consolidation is relatively scarce. This study proposes a novel analytical model for predicting the consolidation behavior of the slurry treated by PHDs‐VP. This model treats the PHDs layer as a continuous drainage layer. Analytical solutions considering the clogging effect and the vacuum preloading process have been derived. The correctness and applicability of the proposed model have been verified through degeneration analysis and comparison with laboratory experimental data. Subsequently, an in‐depth sensitivity analysis of parameters has been conducted to assess the influence on consolidation. The research findings indicate that the clogging effect significantly reduces the consolidation rate, while the influence of the increasing rate in vacuum pressure is relatively minor. Additionally, increasing the slurry filling rate and the PHDs layout density can both accelerate soil consolidation. These findings offer significant guidance for the implementation of PHDs‐VP method in engineering. [ABSTRACT FROM AUTHOR]

To ensure the safety of deep foundation pit construction, this paper proposes a settlement calculation model for deep foundation pits in soft soil areas. In this model, factors such as the non-Darcian flow law of soft soil, the varying boundary drainage capacity, and the construction loads are considered. Among them, the Hansbo's flow and the linear load are used to portray the complicated conditions in real-world engineering, and the continuous drainage boundary is utilized to describe changes in drainage performance of soil boundaries. Comparing the effectiveness of the suggested solution to prior research has confirmed its efficacy. Then, using a number of examples, the consolidation mechanism of soil with continuous drainage boundary is examined in light of Hansbo's flow law and the linear load. The pore pressure in soil layers with continuous drainage boundaries under linear load exhibits a trend of initially increasing and then dropping, according to numerical research. Furthermore, the peak of the increase in pore pressure is substantially impacted by Hansbo's flow equation. The bigger the parameters in the Hansbo's flow law, the longer the linear loading time, and the slower the settlement in the soil layer with the continuous drainage boundary are additional factors. [ABSTRACT FROM AUTHOR]

IntroductionMany theories of consolidation for soils have been proposed in the past, but most of them have ignored the structural characteristics of clay, yet the natural layered soils are widely distributed around the world.MethodsA theoretical model is established to analyze the one-dimensional consolidation behavior of layered soils, in which a time-dependent drainage boundary and the structural characteristics of the soil are taken into account. Using the integral transform and characteristic function methods, the analytical solution is derived, the effectiveness of which is evaluated against the degradation of solutions and the numerical results calculated using the finite element method.Results and discussionFinally, the influences of interface parameter, soil permeability coefficient and soil compressibility on consolidation behaviors are discussed. Results show that in structured soils, early dissipation of excess pore water pressure and consolidation rates are predominantly influenced by interface parameters, permeability, and volume compression coefficients. Higher values of these parameters accelerate early stages of consolidation, which is especially evident in the upper soil layers. Over time, the distinct effects of interface and permeability coefficients on consolidation diminish. Higher volume compression coefficients, while initially beneficial, eventually slow down the consolidation process, indicating an interaction with the ongoing soil structural changes.

Copyright of Engineering Mechanics / Gongcheng Lixue is the property of Engineering Mechanics Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Laboratory one-dimensional consolidation tests were conducted to measure the variation trend of the soil pore pressure at the drainage boundary with time under different magnitudes of loads. Based on the test data, continuous drainage boundary interface parameters under arbitrary loads were inversely derived, the reasonableness of which was verified by comparing the theoretical values of the boundary pore pressure with the experimental results. Moreover, the one-dimensional consolidation model of the layered foundation was established with a continuous drainage boundary. The semianalytical solution of the corresponding model under an arbitrary load was given by using the boundary transformation method. A comparison with degraded results and the finite-element calculation results verified the correctness of the present solutions. Finally, the influences of the interface parameters and loading rate on the soil consolidation behavior were studied, where three different types of loads (i.e., linear, exponential, and simple harmonic) were considered. The results revealed that the consolidation rate reaches the peak value for the linear loading pattern when the loading is completed. Moreover, the exponential load used to describe the surcharge preloading method also positively influenced the theoretical analysis due to its concise expression form. When the simple harmonic load was applied, the excess pore-water pressure in the soil element presented stable periodic vibration after the first cyclic load. In addition, the loading rate and interface parameters exhibited different influences on the consolidation behaviors. The research results of this paper can provide a theoretical reference for the settlement calculation of subgrades during the construction and operation phases. [ABSTRACT FROM AUTHOR]

Conventionally, drainage boundaries are often assumed to be either perfectly permeable or completely impermeable. However, a more realistic approach considers continuous drainage boundaries. In this context, an analytical solution for double drainage consolidation in vertical drains is derived. The proposed method is evaluated against existing solutions and finite element simulations. The study investigates the impact of drainage capacity, soil nonlinearity, smear effect, and well resistance. The results show that the continuous drainage boundary parameters (i.e., b and c) significantly affect the distribution of excess pore water pressure and the consolidation rate. Increasing b and c allows realistic modeling of drainage capacity variations from impermeable to permeable boundaries. Notably, when b ≠ c, the maximum excess pore water pressure plane shifts from the mid-height of the foundation soil, diverging from conventional consolidation theory. Soil nonlinearity (Cc/Ck) and boundary permeability (b and c) jointly affect consolidation. Higher Cc/Ck values correlate with more detrimental consolidation effects. Minimizing disturbance around vertical drains during construction is crucial due to well resistance and smear zone effects, which can significantly slow down consolidation. This study provides an analytical solution considering soil nonlinearity for predicting consolidation in actual engineering scenarios involving vertical drainage trenches. [ABSTRACT FROM AUTHOR]

Based on the double nonlinear consolidation constitutive associated with the compression and permeability coefficients, presented by Mesri and Rokhsar (1974), this paper derives an approximate closed-form solution for the one-dimensional nonlinear consolidation of the arbitrary layered soils incorporating the continuous drainage boundary condition. The approximate closed-form solution is obtained by the homogenization of the boundary conditions and eigenfunction method. A model test is conducted to justify the rationality of the approximation and the continuous drainage condition utilized in this study. The calculated results are also compared with those acquired from the simplified analytical solution and the finite difference method. A parametric study is conducted to investigate the influence of various parameters on the consolidation process. The most significant finding is that the influence of Nq appears to be completely different for the cases when Cc/Ck>1 and Cc/Ck1, the increase of Nq shows an adverse influence on the consolidation, whereas the influence becomes positive when Cc/Ck

Continuous drainage boundary is widely accepted to overcome the shortcoming of the traditional assumption of fully permeable or impermeable drainage boundary in consolidation theories. This study presents an analytical solution for one‐dimensional small‐strain nonlinear consolidation of saturated multi‐layered soil with constant consolidation coefficients under continuous drainage boundary condition. The proposed solution is validated by comparison with the existing solutions in literature, which shows that the existing solutions are special cases of this solution. A parametric study performed on saturated four‐layered soil with continuous drainage boundary indicates that the interface parameter and the loading stress ratio have great influences on the nonlinear consolidation of saturated multi‐layered soil. The present solution can be effectively applied to provide more reasonable design for soil foundation. [ABSTRACT FROM AUTHOR]

Based on the soil nonlinearity assumptions proposed by Mesri, the one-dimensional nonlinear consolidation of double-layered soil is investigated. To better align with engineering reality, a continuous drainage boundary is introduced, bolstering the reliability of the derived solution through comparison against existing findings. Subsequently, the consolidation behavior of double-layered soil is analyzed for the soil permeability, compressibility, nonlinear parameters, and interface parameters. The outcomes elicit a positive correlation between the consolidation rate of the double-layered soil and both the ratio of permeability coefficient from the lower to upper soil layers and the value of the interface parameter. Furthermore, it is observed that a lower compressibility coefficient ratio between the lower and upper soil layers, along with a reduced ratio of compression index to penetration index, both contribute to an increased consolidation rate within the context of double-layered soil. The one-dimensional nonlinear consolidation of double-layered soil is intricate, intertwined with the relative permeability and compressibility of soil layers, and the influence of nonlinear parameters and drainage boundary configuration. Integrating these factors is crucial for analyzing the consolidation traits of double-layered soil, leading to a more precise portrayal of the consolidation behavior of coastal soft soils. [ABSTRACT FROM AUTHOR]

The newly filled soil in reclamation areas shows a significant consolidation effect, resulting in severe ground settlements and inducing extremely adverse impacts on the stability of foundations on site. Based on the continuous boundary conditions, this paper establishes a one-dimensional filled soil-native seabed consolidation theory with consideration of the self-weight of the filled soil and the bedding characteristics of the seabed simultaneously, and derives an analytical solutions to the response of the excess pore water pressure and the consolidation degree through the eigenfunction method. The proposed solution is subsequently verified through the degradation of the boundary conditions and mathematical models. By virtue of the proposed solution, a parametric study is conducted to investigate the influence of the spatio-temporal impact factors (including the self-weight of the filled soil, moduli of the filled soil, time factor, and additional load at ground) on the consolidation. The main conclusions can be drawn as follows: ①The self-weight of the filled soil drives the consolidation of the newly filled ground and should not be ignored in practical engineering. ②The effect of the permeability coefficient on the dissipation of the excess pore water pressure is relatively complicated. In case of change in the penetrability of a certain soil layer, it will have opposite influences on the excess pore water pressure of the overlying and underlying soil layers. ③The volume compressibility of the soil has a significant influence on the excess water pressure. And the influence of the volume compressibility of the deeply buried soil is more significant. ④The additional load caused by, for instance, the stacking at the ground, will slow down the consolidation of the site.

Excavation-induced unloading effects and dewatering-induced groundwater seepage inevitably result in basal soil reverse consolidation in deep excavation. However, this reverse consolidation process is rarely considered because most previous analytical methods were developed based on total stress analyses. This study proposes a one-dimensional reverse consolidation model for basal soil of deep excavation. Based on the consolidation theory proposed by Terzaghi, governing equations of soil reverse consolidation caused by excavation and dewatering were separately established. The continuous drainage boundary was introduced to describe the construction processes. The reverse consolidation responses of basal soil were obtained by superimposing analytical solutions of the excess pore-water pressures that resulted from excavation and dewatering. The proposed model was verified by existing solutions and a well-documented excavation case history. Moreover, the reverse consolidation characteristics of basal soil were investigated by parametric analyses. Results indicate that the excavation-induced variations in pore-water pressure decreased with increasing excavation depth. The final pore-water pressure and effective stress were predominantly affected by excavation duration rather than interval distribution. In addition, a smaller coefficient of consolidation led to lower pore-water pressure and greater effective stress at a given excavation depth. [ABSTRACT FROM AUTHOR]

Conventionally, drainage boundaries are often assumed to be either perfectly permeable or completely impermeable. However, a more realistic approach considers continuous drainage boundaries. In this context, an analytical solution for double drainage consolidation in vertical drains is derived. The proposed method is evaluated against existing solutions and finite element simulations. The study investigates the impact of drainage capacity, soil nonlinearity, smear effect, and well resistance. The results show that the continuous drainage boundary parameters (i.e., b and c) significantly affect the distribution of excess pore water pressure and the consolidation rate. Increasing b and c allows realistic modeling of drainage capacity variations from impermeable to permeable boundaries. Notably, when b ≠ c, the maximum excess pore water pressure plane shifts from the mid-height of the foundation soil, diverging from conventional consolidation theory. Soil nonlinearity (Cc/Ck) and boundary permeability (b and c) jointly affect consolidation. Higher Cc/Ck values correlate with more detrimental consolidation effects. Minimizing disturbance around vertical drains during construction is crucial due to well resistance and smear zone effects, which can significantly slow down consolidation. This study provides an analytical solution considering soil nonlinearity for predicting consolidation in actual engineering scenarios involving vertical drainage trenches.

Adopting the non-Darcy flow presented by Hansbo and considering the nonlinear compression and permeability characteristics of soils, the one-dimensional nonlinear consolidation problem of soft clays is investigated by means of a continuous drainage boundary. The numerical solutions of average consolidation degrees defined by settlement and excess pore water pressure are derived by using the finite difference method, and the correctness of these solutions is verified by comparing them with existing analytical and numerical solutions. Based on the proposed solutions, a parametric study is conducted to study the influence of interface parameter, non-Darcy flow parameter and soil nonlinearity on the consolidation behavior of soft clays. The results show that the solutions based on the continuous drainage boundary can be degenerated into the solutions based on the Terzaghi drainage boundary if the interface parameter is taken as a reasonable value. The soil consolidation behavior considering both non-Darcy seepage and nonlinear characteristics of soil is very complex. [ABSTRACT FROM AUTHOR]

The boundary drainage performance controls the rate of pore water discharge in the soil and plays an important role in the prediction of soil consolidation and settlement. Based on a continuous drainage boundary that can reflect the change of boundary drainage performance with time, a one-dimensional consolidation model of double-layered soil considering non-Darcian flow is established. The finite-difference method and semianalytical method are used to solve the consolidation equation, and the reliability of the two methods is verified by comparing with existing solutions. Based on the proposed solution, the consolidation behaviors of the double-layered soil are explored in depth through a systematic parametric study. The results show that, if the time effect of drainage boundary and the influence of non-Darcian flow are ignored, the estimated consolidation rate is relatively fast in the whole consolidation stage. The non-Darcian flow has a greater influence on soil consolidation under the continuous drainage boundary condition compared with that under the traditional drainage boundary condition. The consolidation rate of the foundation can be improved by appropriately increasing the permeability of the underlying soil layer or decreasing the compressibility of the underlying soil layer. [ABSTRACT FROM AUTHOR]

Soil tends to have nonlinear compression characteristics, and the consolidation laws of soil are different under different compression characteristics. Considering the nonlinear characteristics of soil, variable load and continuous drainage boundary conditions, a one-dimensional consolidation equation is established. Its solutions are obtained by using the unconditionally stable finite difference method and semi-analytical method, and the reliability of the two methods is verified by the degradation of continuous drainage boundary condition and the comparison of the two solutions. Based on the solution of finite difference method, the influences of interface parameter, load parameters and nonlinear parameter on soil consolidation are analyzed in detail. The results show that, the larger the interface parameter of continuous drainage boundary, the greater the dissipation rate of excess pore water and the settlement rate of soil, while the interface parameter has no effect on the final settlement. The excess pore water pressure gradually increases at the loading stage and dissipates at the constant loading stage. With the increase of loading rate, both the peak value of excess pore water pressure and soil consolidation rate increase, indicating that extending the construction period is conducive to reducing the influence of excess pore water pressure. It is difficult to accurately predict the consolidation rate of soil in engineering. The accuracy of soil model, boundary conditions and soil calculation parameters should be ensured when the consolidation theory is used.

Copyright of Journal of Harbin Institute of Technology. Social Sciences Edition / Haerbin Gongye Daxue Xuebao. Shehui Kexue Ban is the property of Harbin Institute of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Central South University is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Based on the soil nonlinearity assumptions proposed by Mesri, the one-dimensional nonlinear consolidation of double-layered soil is investigated. To better align with engineering reality, a continuous drainage boundary is introduced, bolstering the reliability of the derived solution through comparison against existing findings. Subsequently, the consolidation behavior of double-layered soil is analyzed for the soil permeability, compressibility, nonlinear parameters, and interface parameters. The outcomes elicit a positive correlation between the consolidation rate of the double-layered soil and both the ratio of permeability coefficient from the lower to upper soil layers and the value of the interface parameter. Furthermore, it is observed that a lower compressibility coefficient ratio between the lower and upper soil layers, along with a reduced ratio of compression index to penetration index, both contribute to an increased consolidation rate within the context of double-layered soil. The one-dimensional nonlinear consolidation of double-layered soil is intricate, intertwined with the relative permeability and compressibility of soil layers, and the influence of nonlinear parameters and drainage boundary configuration. Integrating these factors is crucial for analyzing the consolidation traits of double-layered soil, leading to a more precise portrayal of the consolidation behavior of coastal soft soils.

The thermal effect can significantly influence the consolidation of the soil, especially in the cold region. Previous studies have established to research that the drops in the ambient temperature would slow down the consolidation process, resulting in the slow dissipation of excess pore water pressure. In addition, the previous studies neglect the final settlement because consolidation is also influenced by thermal effect. In this paper, a closed-form solution to the one-dimensional nonlinear consolidation of soil considering the thermal effect is proposed. In the mathematical framework, the influences of the thermal effect on the compression index, the permeability, and the elastic modulus of the soil are considered. The solution is fully verified by comparing it with the FDM solution neglecting the thermal effect and the classic Terzaghi's solution. An analysis has been carried out to assess the influence of temperature, stress ratios, consolidation time, the ratio of compression index to permeability index, and the interface parameters on the consolidation process. Different from many previous studies overlooking the thermal effect on the modulus of the soil, a model has been developed which points out that the final settlement due to consolidation would vary significantly with the ambient temperature. Therefore, the thermal effect must be considered in the consolidation calculation of the freeze–thaw cycle soil in the cold region. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Harbin Institute of Technology. Social Sciences Edition / Haerbin Gongye Daxue Xuebao. Shehui Kexue Ban is the property of Harbin Institute of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper investigates the one-dimensional rheological consolidation problem of multilayered soils subjected to different time-dependent loadings and continuous permeable boundary conditions. First, by introducing fractional calculus, the conventional Merchant constitutive model is modified to the fractional derivative Merchant (FDM) model, and the newly established model is introduced to describe the rheological characteristics of soil. Subsequently, to simplify the solving process of the consolidation equation, the Laplace transform is utilized to convert the partial differential equations into ordinary differential equations, and the analytical solutions in the Laplace domain are obtained. Furthermore, the solutions in the time domain are obtained by using Abate's fixed Talbot method (AFT method), which is one of the numerical Laplace inversion methods, and the corresponding computer program for the AFT method is attached. A comparison between the degenerated results of this study and those in the literature suggests that the present solutions are more general and applicable. Finally, several instances are provided to study the impacts of model parameters on the consolidation phenomenon. [ABSTRACT FROM AUTHOR]

In conventional consolidation theories, a boundary is simulated as either perfectly pervious or impervious, where the time-dependent drainage capacity at the boundary is ignored. Using the time-dependent impeded boundary condition, it is very difficult to derive solutions analytically. A continuous drainage boundary is proposed in this investigation to characterize the time-dependent drainage behavior at the boundary. The interface parameter is of physical significance, which depends on the properties of both the consolidating soil and the adjacent medium. In this study, two methods are developed to estimate the interface parameter. Back-analysis can be conducted to evaluate the interface parameter based on the variations of excess pore-water pressure from experimental or field measurements. Alternatively, an empirical approach is derived to correlate the interface parameter with the ratio of the coefficient of consolidation and the thickness ratio between adjacent media. The solution is further employed to analyze layered soils with a horizontal drain. It is found that both the plane of maximum excess pore-water pressure and the optimal position of horizontal drain move toward the boundary with a lower drainage capacity with time. A simplified design chart is finally presented to optimize the layout of the horizontal drain in layered clay–drain systems. [ABSTRACT FROM AUTHOR]

Adopting the non-Darcy flow presented by Hansbo and considering the nonlinear compression and permeability characteristics of soils, the one-dimensional nonlinear consolidation problem of soft clays is investigated by means of a continuous drainage boundary. The numerical solutions of average consolidation degrees defined by settlement and excess pore water pressure are derived by using the finite difference method, and the correctness of these solutions is verified by comparing them with existing analytical and numerical solutions. Based on the proposed solutions, a parametric study is conducted to study the influence of interface parameter, non-Darcy flow parameter and soil nonlinearity on the consolidation behavior of soft clays. The results show that the solutions based on the continuous drainage boundary can be degenerated into the solutions based on the Terzaghi drainage boundary if the interface parameter is taken as a reasonable value. The soil consolidation behavior considering both non-Darcy seepage and nonlinear characteristics of soil is very complex.

Copyright of Journal of Central South University is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Engineering Mechanics / Gongcheng Lixue is the property of Engineering Mechanics Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In geotechnical engineering, vertical drainage is the most economical method for accelerating the consolidation of a large area of soft ground. In this study, we analyze the viscoelasticity of the soil and the actual drainage conditions on the top surface of the soil, and then we introduce continuous drainage boundary conditions and adopt a fractional derivative model to describe the viscoelasticity of the soil. With the use of a viscoelasticity model, the governing partial differential equation for vertical drains under continuous drainage boundary conditions is obtained. With the application of the Crump numerical inversion method, the consolidation solution for vertical drains is also obtained. Further, the rationality of the proposed solution is verified by several examples. Moreover, some examples are provided to discuss the influence of interface drainage parameters on the top surface of soil and the viscoelasticity parameters of soil on the consolidation behavior of vertical drains. The proposed method can be applied in the fields of transport engineering to predict the consolidation settlement of a foundation reinforced by vertical drains.

The traditional drainage boundary regards the drainage boundary as completely permeable or completely impervious. However, the drainage boundary is an impeded drainage boundary between completely permeable and impervious in engineering practice. In view of this, a new drainage boundary, namely the continuous drainage boundary, is introduced in this paper to study the consolidation problem of layered soils. First, the governing equations for the one‐dimensional consolidation problem of layered soils subjected to a ramp load are established. Then, the analytical solution of excess pore water pressure and average consolidation degree is derived by means of Laplace transform and matrix transfer method. The present solution is verified by degenerating it and comparing with existing solutions. Based on the present solution, the consolidation behavior of the layered soils is investigated by conducting a detailed parametric study. The results show that, both the interface parameters of boundaries and the stratification of the layered soils can heavily affect the distribution of the excess pore water pressure along the depth, thereby influence the plane of the maximum excess pore water pressure. Therefore, the interface parameters of boundaries and the soil stratification should be comprehensively considered in the optimization for the horizontal drains. [ABSTRACT FROM AUTHOR]

Summary: In engineering practice, a rapid loading rate can result in ground failure when the strength of soft soils is relatively low, and a multistage loading scheme is always utilized to deal with this situation. Firstly, under a multistage load and the continuous drainage boundary, an analytical solution of excess pore‐water pressure and consolidation degree is obtained by virtue of the superposition formula of excess pore‐water pressure, and a more general continuous drainage boundary under arbitrary time‐dependent load is developed. Then, a comparison with existing analytical solutions is conducted to verify the present solution. A preliminary attempt on applying the continuous drainage boundary into the finite element model is made, and the feasibility of the numerical model for the one‐dimensional consolidation under the continuous drainage boundary is verified by comparing the results calculated by FEM with that from present analytical solution. Finally, the consolidation behavior of soil is investigated in detail for different int erface parameters or loading scheme. The results show that, in land reclamation projects, a horizontal drain should be placed close to the boundary with a smaller interface parameter to improve the consolidation efficiency. The degree of consolidation is also related to the applied time‐dependent load and interface parameters. [ABSTRACT FROM AUTHOR]

To comprehensively consider the impacts of stratification, residual pore water pressure, soil nonlinearity, and boundary permeability on consolidation settlement of soft soil foundations for accurate prediction, a continuous drainage boundary condition is proposed in this study that reflects the residual pore pressure under multistage loading, and a nonlinear elastic constitutive model based on the double logarithmic model is adopted to account for the nonlinear consolidation behaviour of soils. A UMAT subroutine is developed based on the proposed boundary condition and nonlinear elastic constitutive model. Subsequently, the developed subroutine is compared with the built-in linear elastic soil constitutive model in ABAQUS and engineering examples. The application of continuous drainage boundaries in stratified foundations is analysed, as well as the influence of factors such as the loading rate and soil nonlinearity on consolidation settlement. The results indicate that, compared to the built-in model, the subroutine developed in this study can be employed to more accurately calculate the nonlinear consolidation of multilayered foundations under multistage loading. By adjusting the loading rate parameter α k , consolidation under different loading conditions can be predicted. Additionally, the proposed boundary condition simplifies the calculations for soft soil foundations with sand layers, providing a novel computational approach for the design of construction loading schemes and long-term settlement predictions in soft soil foundations. [ABSTRACT FROM AUTHOR]

Taking non-Darcian flow and multi-stage loading into consideration, a semi-analytical solution for one-dimensional consolidation of multi-layered soil under continuous drainage boundary based on a linearization method was derived in this paper. The correctness of the proposed solution was verified by comparing with the existing solutions and finite element method results. Accordingly, the influence of soil properties, load parameters, interface parameter and flow parameters on the consolidation characteristics of multi-layered soil was further analyzed. The results showed that the permeability coefficient and flow exponent of the first layer of soil has the most significant influence on the consolidation of multi-layered soil, while the volume compression coefficient of the bottom layer of soil has the greatest influence on the consolidation of multi-layered soil. Continuous drainage boundary, non-Darcian flow and multi-stage loading can all prolong the consolidation process of layered soil. However, the influence of continuous drainage boundary on soil consolidation is reduced when considering non-Darcian flow or multi-stage loading. [ABSTRACT FROM AUTHOR]

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Summary: Traditional consolidation theories cannot provide good predictions of consolidation settlement in land reclamation because of their assumptions that the influence of soil's self‐weight is often neglected, and the drainage boundary is considered as fully pervious/impervious. In view of these limitations, an analytical solution is derived for one‐dimensional self‐weight consolidation problems with a continuous drainage boundary using the finite Fourier sine transform method. Following the classical Terzaghi's small strain theory, the soil's self‐weight is considered to produce consolidation settlement in dredged materials with a constant coefficient of consolidation. The continuous drainage boundary can essentially describe the time‐dependent variation of drainage capacity at the interface between two adjacent soil layers. By reducing the interface parameters, the effectiveness of the calculation is demonstrated against the Terzaghi's solution. The influence of interface parameters and soil's self‐weight stress coefficient on self‐weight consolidation is discussed. As expected, the rate of consolidation considering the self‐weight stress is faster, although the dependency of consolidation rate on the material property of void ratio is neglected. Moreover, the plane of maximum excess pore‐water pressure is estimated as a function of time factor, based on which a design chart is developed to optimize the layout of horizontal drains in land reclamation. [ABSTRACT FROM AUTHOR]

Copyright of Engineering Mechanics / Gongcheng Lixue is the property of Engineering Mechanics Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Based on the double nonlinear consolidation constitutive associated with the compression and permeability coefficients, presented by Mesri and Rokhsar (1974), this paper derives an approximate closed-form solution for the one-dimensional nonlinear consolidation of the arbitrary layered soils incorporating the continuous drainage boundary condition. The approximate closed-form solution is obtained by the homogenization of the boundary conditions and eigenfunction method. A model test is conducted to justify the rationality of the approximation and the continuous drainage condition utilized in this study. The calculated results are also compared with those acquired from the simplified analytical solution and the finite difference method. A parametric study is conducted to investigate the influence of various parameters on the consolidation process. The most significant finding is that the influence of N q appears to be completely different for the cases when C c / C k > 1 and C c / C k < 1. When C c / C k > 1 , the increase of N q shows an adverse influence on the consolidation, whereas the influence becomes positive when C c / C k < 1. The approximate solution derived herein offers a rigorous analytical approach for the double nonlinear consolidation problems of arbitrary layered soils, providing an effective benchmark for comparison and verification of future sophisticated numerical approaches. [ABSTRACT FROM AUTHOR]

To remedy the limitation that the conventional drainage boundary only considers two extreme cases of pervious and impervious boundaries, the consolidation theory of vertical drain is derived by applying the continuous drainage boundary, and its validity is also proven. Based on the obtained solutions, the excess pore water pressure and the average degree of consolidation under the continuous drainage boundary condition are analyzed, and the effect of the drainage capacity of the top surface, the smear effect and the well resistance on consolidation are explored. Furthermore, the practicality of this theory is also validated by the comparison with experimental data. Results confirm that the complete and continuous process of the ground top surface can be changed from no drainage to a complete drainage by adjusting the value of the interface parameter b. Higher value of the interface parameter b means a stronger water permeability of the foundation, resulting in a faster dissipation of excess pore water pressure and a faster consolidation. Meanwhile, the vertical drainage of the vertical drain cannot be neglected in calculation even though vertical drains are based on a horizontal seepage. Moreover, the smear effect and the well resistance play an important role on consolidation.

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This work presents an upgraded one-dimensional (1D) nonlinear rheological system of soft ground consolidation. In the system, the boundaries are characterized by the time-dependent drainage boundary conditions at the surface and bottom of the layer. Meanwhile, the modified UH relationship and non-Newtonian index flow model are used to simulate the viscous effect of clay and the flow of excess pore-water during consolidation, respectively. Then, two numerical discretization formats of the system, namely the finite volume method (FDM) and finite difference method (FVM), are given, and corresponding calculation programs are compiled. The model solutions have been validated by degraded analytical solutions, FDM and FVM comparison solutions, and available laboratory data. Further, the consolidation behaviour under different model parameters is illustrated. The calculated results indicate that the change of interface parameters and flow mode does not influence the final foundation settlement, but both significantly affect the overall dissipation process of EPWP of soils. At last, an efficient method for determining CDB parameters is proposed and verified by available test data. [ABSTRACT FROM AUTHOR]