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In this study, a two-dimensional consolidation solution for geotextile tubes filled with fine-grained material was presented. The solution is based on a combination of various methods that were modified or extended to take into account the change in tube shape, the nonlinear interaction between the soil and geotextile, and the water content distribution of the tube during consolidation. Using the proposed solution, the effect of various necessary input parameters was investigated. Thereafter, numerous dewatering and consolidation properties of various combinations of geotextiles and fill materials were obtained from several tests such as the half cross-section test, hanging bag tests, and geotextile tube demonstration test. Results of the study have shown that the method presented in this study can well-represent the consolidation behavior of geotextile tubes filled with fine-grained material.

The performance of geotextile tubes is affected by many factors such as the pumping pressure, fill material and geotextile properties, and so on. Hence, obtaining hydraulic compatibility between geotextiles and fill materials containing a variety of coarse and fine particles – that is, silty sand – is complex. For this reason, the modified geotextile tube (MGT) was invented to optimize the filling and dewatering or consolidation performance of geotextile tubes. To assess the behavior of MGTs, experimentation and theoretical analysis were conducted. The MGT retention performance, filling time, and water pressure were evaluated through a geotextile bag experiment while the MGT geometry, tension force, strain, water content distribution, and consolidation performance, were investigated through a parametric study. The two-dimensional MGT solution presented in this study is based on a combination of various modeling concepts that were modified or extended to be able to sufficiently describe the MGT behavior. Results showed that the performance of geotextile tubes can be optimized in a variety of ways by interchanging the geotextile placement, by changing the circumferential lengths, and by using geotextiles with different properties. With the methods presented in this study, modified geotextile tube design is made possible.

A new coupling method, immersed moving boundary–discrete element method–lattice Boltzmann method (IMB-DEM-LBM), is proposed to simulate particle flow for application in soil mechanics or coastal engineering. In this study, LBM fluid is simulated on the regular Eulerian grid and Lagrangian particle motion is governed by DEM while IMB couples the two algorithms. The new method is promising and robust as it resolves numerical instability near the particle boundary caused by mesh distortion in the conventional grid method. In IMB, the interface lattice solid fraction determines the distribution function ratio of non-equilibrium bounce back and Bhatnagar-Gross-Krook (BGK) collision. The non-equilibrium bounce back at moving boundary results in the fluid momentum change and contributes to the hydrodynamic force on particle. For numerical stability, this paper introduces the hydrodynamic force calculation concept from IB (immersed boundary method) to IMB, and at the same time, proposes a new solid fraction calculation method for sphere that divides the intersection into simple sector and triangle, as well as calculates the intersection area by vector. With this method, approximate inaccuracy is overcome while complicated integration is avoided.

The computer program pile negative skin friction (PileNSF) was developed by the authors to predict the bearing capacity of a pile embedded in a consolidating ground due to surcharge loading. The program uses a one-dimensional analytical soil-pile model, which was formulated based on the nonlinear load-transfer method and Mikasa’s generalized one-dimensional consolidation theory. To investigate the development of negative skin friction on single piles, as well as to validate the computer program (PileNSF), a laboratory model test was performed in this study. The clay layer was subjected to increasing surcharge loads to simulate actual field conditions. Results showed that as excess pore pressure decreases and as surcharge load increases, the dragload and downdrag on pile increases. The measured values of soil settlement, excess pore water pressure, and axial force on pile were compared with the predicted values obtained from the computer program. The results of the computer program (PileNSF) showed to be in good agreement with the measured data. Therefore, negative skin friction on single piles can be effectively predicted using the computer program, PileNSF, provided that reasonable parameters are used in the analysis. After validating the program, a parametric study was carried out to study the influence of various pile design parameters on negative skin friction.

Two-dimensional analytical and numerical solutions for determining the geometric dimensions and stresses of geotextile tubes are reviewed. Conventional one-dimensional (1D) approximation of the average drop in height (consolidated height) of geotextile tubes was also reviewed in this study. Densification modeling of the fill material based on areal-strain analysis is introduced. Leshchinky et al.'s approximation method considers only the vertical movement of the densifying material in the analysis. The areal-strain method offers an alternative analysis approach wherein both the vertical and lateral movements of the densifying fill material are considered. The geotextile tube is assumed to be resting on a rigid horizontal foundation and analyses for both filling and densified stages treats the internal material as liquid in order to apply normal pressure to the tube. Parametric cases for the densification of geotextile tube fill are presented. Results show that the degree of tube height reduction decreases as the density of the slurry fill is increased. Large-scale tests have been conducted on composite geotextile tubes made of outer woven and inner non-woven polyester (PET) material. The tubes were 10 m and 25 m long having theoretical diameters of 3.0 m and 5.0 m, respectively. The validity of the solution for densification analysis was demonstrated by comparing the numerical results to those of the field test. The agreement between the numerical results and field measurement data is fairly acceptable.

A series of injection and drainage test were conducted on an circular acrylic tube to investigate the pressure generated by the accumulated fill materials inside a circular acrylic tube structure. The acrylic tube was filled by means of gravity filling with a slurry material having an average water content of 700%. The water head during the filling process was 1.8m and the bottom pressure during initial filling was 20.18kPa. The recorded stress at the sides of the acrylic tube was 17.89kPa during the filling process and was reduced to 13.58kPa during the leaving process. Continuous drainage of the acrylic tube has greatly influenced the stresses around the tube structure. As the water is gradually allowed to overflow, the generated pressure at the topmost pressure sensor of the tube was reduced further to 2.17kPa. Eventually, the initially liquid state slurry material transforms into plastic state after water has dissipated and substantial soil particles are deposited in the acrylic tube. The final water content of the deposited silt inside the acrylic tube after the test was 42%. It was found that the state of stresses(geo-static earth pressures) in the acrylic tube was anisotropic rather than isotropic.

Comparative study has been performed to investigate the behavior of dredged fills on rigid (Model 1) and flexible (Model 2) containers. The study was focused on the sedimentation of soil fills and the development of total stresses. Model 1 is made of an acrylic cylinder and Model two is a scale-size geotextile tube. Results indicate that for rigid containers, significant decrease of the sediment height is apparent during the dewatering process. On the other hand, because the geotextile is permeable, the water is gradually dissipated during the filling process on flexible containers. Hence, significant loss in the tube height is not apparent during the duration of the test. Pressure spikes are apparent on rigid containers during the filling process which can be attributed to the confining effect due to hydrostatic pressure. For the flexible containers, the pressure readings gradually increases with time during the filling process and normalize at the end on the filling stage. No pressure spikes were apparent due to the gradual dissipation of pore water pressure.

Analytical solutions for modeling geotextile tubes during the filling process and approximation method to determine the densified tube shape are reviewed. The geotextile tube filling analysis is based on Plaut & Suherman\'s two-dimensional solution for geotextile tubes having a weightless and frictionless inextensible membrane resting on a rigid horizontal foundation subjected to internal and external hydrostatic pressures. The approximation for the densified tube shape developed by Leshchinsky et al. was adopted. A modified method for approximating the densified tube shape based on an areal-strain deformation analysis is introduced. Design diagrams useful for approximating geotextile tube measurements in the design process are provided.

Geotextile tubes are basically a huge sack filled with sand or dredged soil. Geotextile tubes are made of permeable woven or non-woven synthetic fibers (i.e., polyester or PET and polypropylene or PP). The geotextile tubes' performances in strength, dewatering, retaining solid particles and stacked stability have been studied extensively in the past. However, only little research has been done in the observation of the deformation behavior of geotextile tubes. In this paper, a large-scale apparatus for geotextile tube experiment is introduced. The apparatus is equipped with a slurry mixing station, pumping and delivery station, an observation station and a data station. For this study the large-scale apparatus was utilized in the studies regarding the stresses on the geotextile and the deformation behavior of the geotextile tube. Model tests were conducted using a custom-made woven geotextile tubes. Load cells placed at the inner belly of the geotextile tube to monitor the total soil pressure. Strain gauges were also placed on the outer skin of the tube to measure the geotextile strain. The pressure and strain sensors are attached to a data logger that sends the collected data to a desktop computer. The experiment results showed that the maximum geotextile strain occurs at the sides of the tube and the soil pressure distribution varies at each geotextile tube section.

The typical design of ground improvement with prefabricated vertical drains (PVD) and surcharge preloading involves a series of deterministic analyses using averaged or mean soil properties for the various combination of the PVD spacing and surcharge preloading height that would meet the criteria for minimum consolidation time and required degree of consolidation. The optimum design combination is then selected in which the total cost of ground improvement is a minimum. Considering the variability and uncertainties of the soil consolidation parameters, as well as considering the effects of soil disturbance (smear zone) and drain resistance in the analysis, this study presents a stochastic cost optimization of ground improvement with PVD and surcharge preloading. Direct Monte Carlo (MC) simulation and importance sampling (IS) technique is used in the stochastic analysis by limiting the sampled random soil parameters within the range from a minimum to maximum value while considering their statistical distribution. The method has been verified in a case study of PVD improved ground with preloading, in which average results of the stochastic analysis showed a good agreement with field monitoring data.

In this study, two different types of dredged fill injection methods are introduced and filling experiments were conducted to analyze the impact of each technique to the distribution and deposition of dredged soil fill and how it influence the final tube shape. Two transparent plastic tubes were fabricated to observe the deposition behavior of the deposited fill material. Both tubes measured 4.0 meters in length (L) and has vinyl tube diameters (D) of 0.5m and 0.7m. T-type and I-type inlet system are also introduced in this paper. The influence of this inlet systems to the distribution and deposition behavior of dredged soil fill inside the vinyl tubes were observed during the experiment. After the sedimentation of the slurry mixture, the water on top of the soil sediments are removed and the slurry mixture was re-injected into the vinyl tube, this process was carried out repeatedly. The shape changes of the vinyl tube, e.g. the changes in both tube height and width, are constantly monitored after each slurry injection and water draining phases. Crater formation was observed in the case of I-Type inlet system and a non-uniform sediment distribution occurred. For the diffusion deposit of soil particles to long distance are minimal shape technique using the T-Type inlet system. Therefore the undrain filling height ratio () was found to be around 0.54 to 0.64 and the horizontal strain ratio () ranges from 1.45 to 1.54. The filling soil height is proportional to dredged-material filling phases, but, horizontal strain ratio is constant or inversely reduced so that the center of tube body is raised in the upward direction.

Geosynthetic reinforced soil (GRS) walls have been increasingly applied recently due to its numerous geotechnical engineering applications. However failure occurs in some cases of constructed GRS walls. These GRS wall failures are mostly due to the unpredictable characteristics of intensive rainfall. Hence, the need for new and innovative ideas for rehabilitation methods has been getting attention. This paper introduces a case study for the design and restoration method of collapsed GRS wall using Limit equilibrium and Numerical Analyses. Restoration method includes: (1) soil nailing without backfill excavation and (2) reconstruction with GRS wall after collapsed backfill excavation. Analyses results show minimal horizontal displacements and shear strain on the reinforced concrete facing for the restoration case with soil nailing. On the other hand, horizontal displacements are developed in the middle of the mortar block facing and shear strains are developed at the bottom facing with spiral curves for the reconstructed GRS wall after collapsed backfill excavation. Therefore, the collapsed GRS wall was restored with the soil nailing without backfill excavation and its construction procedures are discussed in this paper.

In this paper, the influencing factors for the decision of the embankment construction method utilizing geotextile tube were studied by analyzing the application and economic considerations based on the construction practices of the geotextile tube filled with dredged soil in the domestic and international. In the domestic case, cost savings of 40 to 50% is attained by applying geotextile tubes in the embankment construction and in the international case, the amount of quarry materials was reduced from 20 to 70% by replacing the core of the embankment with geotextile tube. As a result, utilization of geotextile tube filled with dredged soil should be considered in a very large construction site with a quarry-to-site delivery distance of more than 16∼25km. The construction scale and delivery distance were found to be important influencing factors for the decision of the embankment construction method utilizing geotextile tube filled with dredged soil.

A geotextile tube is a type of geocontainer typically filled with sandy slurries and fine-grained dredged sediments. Its performance in strength, dewatering, fine-particle retention, and stacked stability has been studied extensively. However, very little is understood about the shape-deformation behavior of geotextile tubes. In this paper, slurry-settlement, constant head permeability, and seepage-force tests were conducted to determine the geocontainers’ geotechnical design parameters. The characteristics of the dredged fill material determined from the slurry-settlement, constant head permeability, and seepage-force tests are presented. Large-scale tests on model geotextile tubes were also conducted. A large-scale apparatus for geotextile tube–filling test simulation is introduced. The apparatus consists of a slurry mixing station, a pumping and delivery station, a geotextile tube–filling station, and a data station. The results of the model tests conducted on a transparent geobag (undrained co...

The inability to evaluate the effects of the various uncertainties due to spatial and material variability of the soil and pile properties in the axial load capacity of a pile foundation had led some designers to adopt higher global factors of safety in design, which may be conservative and uneconomical if it were not properly evaluated. In addition, the use of lower factors of safety in pile design is often traditionally justified only by the performance of specific pile load tests. This study presents the application of probabilistic analysis based on Stochastic Finite Element Method (SFEM) and Monte Carlo Simulation (MCS) in the selection of economical factors of safety for the geotechnical design of pile axial load capacity. The SFEM is implemented by a coupling between the reliability algorithm with the MCS technique in MATLAB® and the OpenSees finite element program. A probabilistic method of pile analysis evaluates the risk, reliability, or probability of failure associated with the selection of lower factors of safety in design. The results of a probabilistic method of pile capacity evaluation then provide guidance in the selection of a more reliable, unconservative, and economical factor of safety at an acceptable level of risk by making cost comparisons with available options for design.

A modified procedure is presented in this study to evaluate the equivalent top-down load-displacement curve in a bottom-up pile load test considering elastic shortening. On the basis of the results of a parametric study on a bored pile in normally consolidated cohesive soils under undrained conditions, varying shear strength distribution and pile slenderness ratio, it was concluded that the pile shortening caused by the skin-friction component of the load in a top-down test can be related to the measured elastic shortening in a bottom-up test. A λ-factor is used to define this relationship, that is, the ratio of the top-down to bottom-up pile shortening. The factor λ=1.0 is used for the case of a pile in soil with uniform shear strength profile, λ=2.0 for linear profiles, 1.0 2.0 for nonlinear profiles varying below linear. In addition, the method suggests taking the corresponding readings of the skin-friction load component from the upward displace...

With a rigid pile assumption, the equivalent top–down load–settlement curve constructed from the results of a bidirectional or bottom–up pile load test does not fully consider the total elastic shortening when all the load components from skin-friction and end-bearing are applied downward at the pile head. In effect, the equivalent curve constructed by the original method suggested from the Osterberg test showed a much stiffer curve compared to the top–down curve. Design charts are provided in this paper from the results of a parametric study on bored piles in order to approximately evaluate the λ -factor that is used to estimate the top–down pile shortening from the bottom–up shortening due to the skin-friction component of the load. It has been shown that the λ -factor varies with the distribution of the undrained shear strength profile, pile slenderness ratio, and mobilization of the skin-friction resistance. In addition, the pile shortening due to the end-bearing load component is added to the top settlements by treating the pile as an elastic column. A modified method for the construction of the equivalent top–down load–settlement curve is presented that considers the elastic pile shortening and validated with the measured top–down load–settlement curve from pile load tests.

The interface boundary relations are derived in this study for the numerical analysis of one-dimensional consolidation in multilayered clay profiles. The finite difference solutions are formulated based on Mikasa’s consolidation equation with infinitesimal strains and constant consolidation parameters under the same fundamental assumptions and limitations of the classic Terzaghi equation. Numerical examples are presented for multilayer clay profiles under single and double drainage conditions that validate the predicted excess pore pressures, strains, settlements, and rates of consolidation using interface boundary relations in terms of infinitesimal strains that are equivalent to those expressed in terms of excess pore pressures.

The development of dragload and downdrag on single piles in consolidating ground is investigated in this study with a simplified one-dimensional soil-pile model that combines the nonlinear load transfer method and finite strain consolidation theory to analyze soil-pile interaction under the effects of negative skin friction. In order to directly relate the soil settlements and effective stresses through the strain as a function of time and depth during the consolidation process, the prediction of the soil settlements imposing downdrag are based on Mikasa’s generalized one-dimensional consolidation theory that are formulated in terms of finite strain. An illustrative example and a case study of test pile were analyzed and predicted results of dragload and pile shortening by the presented model were shown to be in fair agreement with measured reference data. The model presented in this study offers a simple and flexible method for the analysis of a variety of soil-pile interaction problems under negative skin-friction that can account for nonlinearity of the soil and pile, a rigid and deformable bearing stratum, and can be applicable for the analysis of floating and end-bearing piles as well as for shafts socketed in rocks.

Typical wireless sensor networks used in structural monitoring are continuous types wherein data transmission is progressive at all time that may include irrelevant and insignificant data and information. Continuous types of wireless monitoring systems often pose problems of handling large-sized data that may deteriorate the performance of the system. The proposed method is to suggest an event-triggered monitoring system that captures and transmits relevant data only. An error signal generated by the Principal Components Analysis (PCA) is utilized as an index for event detection and selective data transmission. With this new monitoring scheme, the remote server is relieved of unwanted data by receiving only relevant information from the wireless sensor networks. The performance of the proposed scheme was verified with simulation studies.

Recently, cabled-suspension bridges and suspension bridge have been increasingly built in korea. But such structures were often damaged by fire due to car collison. In this study, the cabled-suspension bridges constructed under the kind of the project of national road aggrandizement are modeled using Solid Works 2007. The COSMOS FloWorks 2007 software are used for Heat Transfer Analysis and Thermal Stress Analysis. The safety of wire, HDPE pipe and stainless steel pipe are investigated. The major variables for the analysis are the temperature of the heat source, the distance between the fire-proof bulk head and the heat source, wind velocity, and the height of the end of Stainless steel pipe.

A modified analytical model is proposed in this study for the analysis of pile axial load capacity with the load transfer method using nonlinear T-z and Q-z curves to model soil-pile behavior in skin friction or side shear and end bearing respectively. The method uses a three-dimensional (3D) pile model using solid finite elements with nonlinear load transfer curves resolved into components and mobilized around the pile perimeter. The use of multiple T-z component springs is demonstrated to accurately capture the total side resistance of the pile. The 3D pile method produces results of predicted pile axial load capacities from the load-settlement curves comparable to the one-dimensional analysis (1D) method. For a combined vertical and lateral loading on the pile, the proposed 3D pile method can address the limitation of the 1D pile method having vertical and lateral springs only acting at the pile center without rotational springs, which neglects the contribution of the side shear in the computation of pile bending moments. In the case of 3D pile model the moment or couple developed by the side shear around the perimeter can be taken into account, where this moment can be significant especially in strong soil material or in the case of large diameter pile/shafts.

Scouring is a significant problem on river bank and coastal protection systems. Severe scouring can cause damaging consequences to geotextile tube embankment structures. In this study, five case scenarios of an embankment system supported by stacked geotextile tubes were analyzed using a commercially available finite-element analysis software. These case scenarios include (1) conventional geotextile tube stacking on ground base foundation; (2) geotextile tube stacking on gravel bedding foundation; (3) geotextile tube stacking on excavated foundation; (4) geotextile tube stacking on excavated foundation with gravel bedding; and (5) fortification of stacked geotextile tubes by riprap protection. Each case scenario is simulated under normal loading and critical loading conditions with and without scouring at the base toe of the embankment system. Results suggest that the potential problems that occur during scouring and critical states of the embankment system instigate failures that could destabiliz...

Sensor networks are usually composed of tens or thousands of tiny devices with limited resources. Because of their limited resources, there will often be some faulty nodes within the network. As nodes in some certain regions rely on each other to route the information gathered by different sensors to a base station (sink), the network should be able to detect a non-operational node in order to determine new paths for routing the information. Failure detection, which identifies the faulty nodes, is rather necessary in sensor networks and a very important research issue. The detection of a non-operational node can be performed using Consensus Algorithm with the purpose of achieving agreement about a node which is supposed to be faulty (non-operational). In this work, we discuss the application of a Consensus Algorithm to sensor node called "mote". Our experimental results show that it works efficiently for identifying faulty nodes in sensor networks.

Concrete-Face Rock-Fill Dams (CFRDs) are rock-fill dams with watertight-concrete slabs on its upstream slope instead of its cen tral earth cores. The design for CFRDs are still largely empirical and typically based on past experiences. This paper presents a de scription of the concrete face slabs and leakage behaviors of two post-constructed CFRDs based on the data gathered through instrumentati on during the initial impoundment. The results show that the strain on the concrete face slab and the horizontal displacements of the vertical slab joints are slightly affected by both the seasonal temperature change and water loading during the initial impound ment. The deformation of perimetric joints are less affected by the temperature change, however it is significantly affected by the water loading during the initial impoundment. The leakage rate is significantly affected by the hydrostatic load and the deformation of the p erimetric joints.Key words : CFRD, Rockfill, Dam, Concrete face slab, Leakage초 록차수기능을 점토 코아 대신 상류사면의 콘크리트 슬래브로 수행하는 콘크리트 표면차수벽형 석괴댐의 설계는 이론보다는 사례와 경험에 크게 의존한다. 본 연구에서는 두 개의 CFRDs에서 준공 후 초기 담수기간에 계측된 데이터를 근거로 콘크리트 슬래브와 누수량 거동을 분석하였다 . 분석결과 슬래브의 변형률과 수직이음부의 수평변위는 미미하게 계절적인 온도 변화와 저수위면 증가에 의한 담수하중의 영향을 받고 , 주변이음부의 변형은 온도 변화의 영향은 미미하고 담수하중의 영향을 크게 받는 것으로 나타났다 . 그리고 누수량은 담수하중에 따른 주변이음부의 변형에 의한 영향을 크게 받는 것으로 나타났다. 검색어 : 콘크리트 표면차수벽형 석괴댐, 록필, 댐, 콘크리트 슬래브, 누수량