Compressible Foundation Research Articles

Self-Derived Wavelet Compression and Self Matching Reconstruction Algorithm for Environmental Data in Complex Space of Coal Mine Roadway

A crucial assurance for coal mine safety production, prevention and control, and rescue, which is the fundamental tenet of implementing intelligent coal mining, is the safety, stability, and quick transmission of coal mine roadways. However, because of the complex structure of the roadway environment, such as limited and variable space and numerous pieces of equipment, the wireless communication network is affected by the environment, the data transmission channel characteristics are complex and variable, and the existing data transmission methods are weak in adapting to the changing channel. These factors result in poor stability of the transmission of coal mine roadway environment detection data in the wireless communicative network. As a result, this article investigates the wireless communication systems’ real-time transmission in the intricate environmental setting of a coal mine. Based on the application of multiscale wavelet theory in data compression and reconstruction, an adaptive multiscale wavelet compression model based on the wireless data transmission channel is proposed, with an improved Huffman data compression coding algorithm derived from the multiscale wavelet, so that the environmental data meet the wireless communication channel transmission capability. The proposed algorithm boosts the compression ratio and adaptability of environmental data. A self-matching wavelet reconstruction algorithm is developed to achieve real-time and accurate data reconstruction following self-driven wavelet decomposition. The compression and reconstruction experiment performed during real-time wireless transmission of gas concentration data reveals that the original signal’s compression ratio reaches 74% with minor error and high fidelity. The algorithm provides the theoretical foundation for compression and reconstruction in complex coal mine environments for accurate, stable, and real-time data transmission. It is critical for ensuring reliable data transmission in safe production, prevention and control, rescue, and other operations, and it provides theoretical and technical support for intelligent coal mining.

Field study of pile – prefabricated vertical drain (PVD) interaction in soft clay

Piles and prefabricated vertical drains (PVDs) are two well-established inclusions used by geotechnical practitioners when dealing with soft compressible foundations. Induced movements in highly compressible soil can adversely influence the pile response by inducing additional movements and stresses in the piles. Especially, undesirable soil–pile interaction often leads to the development of excess pore-water pressure during pile installation and negative skin friction caused by the settlement of compressible soil surrounding the piles. Additional drainage by PVDs prior to the installation of a pile could reduce excess pore-water pressure, lateral soil movement, and negative skin friction on the pile. In this paper, full-scale field testing on two trial embankments built on soft soil is reported and the relative behaviour of these two embankments is compared and discussed. Soft soil underneath both embankments was consolidated before one pile was installed at the centre of each embankment. The pore-water pressure, lateral soil movement, surface settlement, and associated strain at the pile shaft were recorded. The pile capacity was tested immediately and 3 h after pile installation. The monitoring and testing results indicated that preconsolidation with PVDs before piling can effectively reduce the excess pore-water pressure, lateral soil movement, and downdrag on the pile.

A statistical analysis on concrete cut-off wall behaviour

Concrete cut-off walls are a well-established technique for forming seepage cut-off in pervious and compressible foundations in newly constructed dams. This study investigated the behaviour of cut-off walls on the basis of statistical analysis. A set of monitoring records and construction details of 43 case histories of in-service concrete cut-off wall constructed in the past 50 years were gathered. Detailed statistical analyses of horizontal displacement, crest settlement, cracking behaviour and stress of the walls were performed based on the case histories. Loading characteristics and relative settlement between the wall and the alluvium foundation were analysed. The statistical analyses also attempted to identify quantitatively the major factors affecting the wall behaviour; these factors include wall location, wall material, foundation deformation characteristics, wall depth and valley shape. The wall location was found to be the deterministic factor that affects the wall behaviour. The findings and results of this study provide a significant insight into concrete cut-off wall behaviour and provide a valuable reference for future wall design and construction.

Calculating methodology of large base slabs: compressible strata capacity and foundation settlement

The paper focuses on determining foundation active zones and calculating foundation settlement which is the question of great scientific and practical interest. According to existing methodologies, researchers apply the theory of homogeneous isotropic linear-deformable medium to determine the deformation of soil foundations. In this study the authors propose to use the theory of soils compression seal and its one-dimensional problem solution to calculate the sediment of large base slabs. To justify this methodology, the authors specify the minimum size of foundation slabs. They analyze the Boussinesq's Formula and prove that compacting pressure is evenly distributed throughout the area of the slab bottom. The researchers delimit concepts of the active zone and the compressible strata. It is assumed that the compressible strata is a part of the active zone. The existing methods on calculating compressible strata capacity introduced by N.A. Tsytovich and K.E. Egorov (SP 22.13330.2016) are also analyzed in the paper. Besides, formulas of determining compressible strata capacity and of calculating slab foundation settlement are presented. Calculation results of this methodology and the method suggested in the existing code specification (CS) are produced and compared. The researches come to the conclusion that, according to CS, compressible strata capacity increases with the increase of foundation space under the same load. This corresponds to the theory of linear-deformable half-space. The authors believe that the size of slab foundation settlement depends only on the compacting pressure capacity (which coincides with the Winkler's hypothesis), and on the properties of foundation soils. The authors assign the application area of the spatial problem solution for calculating foundation settlement.

LOAD TRANSFER PLATFORMS - COMPARISON OF DESIGN METHODS

Constructing embankments on compressible foundation soil normally requires soil improvement measures to reduce the amount and duration of settlement. In the most difficult cases, the soil is improved by using pile foundations. When constructing pile foundations, it is necessary to ensure efficient load transfer from the embankment to the piles, which can be achieved using reinforced soil construction with geosynthetics as reinforcement material. In this paper, we compare the calculations of a bearing capacity of such a platform according to the British and the German standards on the example of a level crossing over a railway line. We describe other calculation methods, critically reviewing the fundamental mechanisms of the reinforcement effects in the calculations.

Sense standards, recognition of textual information and its compression based on knowledge of synonymy

This paper presents a method for revelation a sense standard based on a set of semantically equivalent phrases of a subject-oriented language as a foundation for text recognition and compression. It suggests using this method to organize the basic components of a software knowledge control system based on test tasks of the open form.

RESEARCH ON DIFFERENTIAL CODING METHOD FOR SATELLITE REMOTE SENSING DATA COMPRESSION

Abstract. Data compression, in the process of Satellite Earth data transmission, is of great concern to improve the efficiency of data transmission. Information amounts inherent to remote sensing images provide a foundation for data compression in terms of information theory. In particular, distinct degrees of uncertainty inherent to distinct land covers result in the different information amounts. This paper first proposes a lossless differential encoding method to improve compression rates. Then a district forecast differential encoding method is proposed to further improve the compression rates. Considering the stereo measurements in modern photogrammetry are basically accomplished by means of automatic stereo image matching, an edge protection operator is finally utilized to appropriately filter out high frequency noises which could help magnify the signals and further improve the compression rates. The three steps were applied to a Landsat TM multispectral image and a set of SPOT-5 panchromatic images of four typical land cover types (i.e., urban areas, farm lands, mountain areas and water bodies). Results revealed that the average code lengths obtained by the differential encoding method, compared with Huffman encoding, were more close to the information amounts inherent to remote sensing images. And the compression rates were improved to some extent. Furthermore, the compression rates of the four land cover images obtained by the district forecast differential encoding method were nearly doubled. As for the images with the edge features preserved, the compression rates are average four times as large as those of the original images.

Track Stabilisation with Geosynthetics and Geodrains, and Performance Verification through Field Monitoring and Numerical Modelling

All over the world, ballasted railway tracks form one of the major transportation networks designed to provide heavy haul freight and passenger traffic. However, large cyclic loading from heavy axle trains operating at high speeds often causes excessive deformation and degradation of ballast, as well as unacceptable differential settlement of compressible foundation and, or pumping of the soft subgrade soils. The problem becomes more severe under high impact loads due to rail or wheel imperfections, causing accelerated ballast breakage. A proper understanding of load transfer mechanisms and their effects on track deformations are essential prerequisites for minimising maintenance costs. The field trial at Bulli demonstrated that for trains with wheel flats, extremely high stresses were transmitted to the ballast layer. Installing resilient mats such as rubber pads (shock mats) in rail tracks can attenuate impact forces and consequently mitigate particle degradation. In view of this, a series of laboratory tests were carried out using a unique large-scale drop-weight (impact) rig to evaluate the role of shock mats. The field trial also showed that the moderately-graded recycled ballast, when used with a geocomposite layer, could perform well in comparison with traditionally uniform fresh ballast. Both Class A predictions and field measurements at Sandgate proved that relatively short vertical drains would be sufficient to dissipate cyclically induced pore pressures, curtail the lateral movements, and increase the shear strength and bearing capacity of the subgrade. In summary, this invited Special Paper describes in detail the large-scale laboratory tests imperative for material characterisation, fullscale instrumented field trials for performance verification, elasto-plastic finite element analyses for predicting the behaviour of tracks stabilised using shock mats, and geosynthetic products including grids and prefabricated drains.

Exhumed Geogrid-Reinforced Retaining Wall

An instrumented geogrid-reinforced wall constructed on a highly compressible foundation was deconstructed 16 months after its completion, providing a unique opportunity to exhume and examine the instrumented geogrids that were used to construct the wall. The objectives of this post mortem study were: (1) to inspect the condition of the strain gauges that were attached to the geogrid layers before construction and to verify the reliability of their output; (2) to develop a procedure in which the residual (plastic) strains along exhumed geogrid panels could be determined; and (3) to assess the in situ strain and force distribution along geogrid panels based on the measured residual strains from the exhumed geogrids. After exhumation, it was observed that many of the attached strain gauges failed due to full or partial debonding from the geogrid, thus rendering outputs which potentially underestimated the actual strain. Combining aperture measurements of virgin and exhumed geogrids, all from the same manufacturing lots, enabled the assessment of residual strains following stress relaxation. Laboratory simulation of loading and unloading, including creep and relaxation, yielded a relationship between the measured residual strains and the in situ strain and force distribution; i.e., the residual strain fingerprint provided insight into the behavior of the geogrids within the wall prior to its deconstruction. The mobilized maximum tensile strains in the geogrid panels along the height of the wall were roughly uniform, in the range 4±1%. These findings imply that if the same type of reinforcement had been used throughout the height of the wall, the mobilized force along the height would have been relatively uniform. The back-calculated maximum force in the geogrids indicated that the factor of safety on the long-term strengths of the geogrids ranged from about 1.4 on the stronger/stiffer geogrid to about 1.8 on the weaker/softer geogrid.

Consolidation of a Double-Layered Compressible Foundation Partially Penetrated by Deep Mixed Columns

Deep mixed columns often penetrate partially into the soft soil as floating columns due to the depth of the end-bearing layer. Partially penetrated soft soil by columns and the underlying compressible soft soil create a double-layered compressible foundation. So far, no reasonable solution is available to estimate the consolidation of such a double-layered foundation. This paper proposes an analytical solution for consolidation of a double-layered compressible foundation partially penetrated by deep mixed columns considering one-side or two-side vertical drainage The Laplace transform method was used to solve the consolidation equation for the double-layered system while Stehfest's algorithm was used to solve the inverse Laplace transform for time-dependent loading. A consolidation algorithm was used to calculate the time-settlement relationship of an embankment constructed upon the double-layered foundation partially penetrated by deep mixed columns. The calculated settlements were compared well with field measurements.

Influence of Boundary Conditions on the Behavior of an Anchored Reinforced Earth Wall

The finite element model is used to simulate the behavior of the full scale instrumented anchored reinforced wall. The validated finite element model is then used to carry out parametric studies to ascertain the influence of the boundary conditions on the behavior of the wall. The boundaries at the crest, facing and base of the wall are varied to study their effects. At the crest of the wall, slope surcharge of various geometrical dimensions are imposed. At the facing of the wall, the boundary is allowed to yield laterally by inserting a compressible geoinclusion at the back face of the wall panels. Meanwhile, at the base, the boundary is allowed to yield vertically by allowing the wall to sit on a compressible foundation soil. The behavior of the wall is determined in terms of the tensile stress distribution developed in the reinforcing bars, the summation of the maximum tension in the reinforcing bars, the summation of the tensions developed at the connection to the facing panels, the lateral movement at the facing and the vertical movement at the base.

Settlement of Dredged and Contaminated Material Placement Areas. II: Primary Consolidation, Secondary Compression, and Desiccation of Dredged Fill Input Parameters

This paper presents practical applications of PSDDF (Primary Consolidation, Secondary Compression, and Desiccation of Dredged Fill), which is described in a companion paper by the writers. In addition, consolidation and desiccation parameters for 27 dredged materials are presented from 20 U.S. Army Corps of Engineers placement areas to facilitate usage of PSDDF. The consolidation parameters of three cohesionless soils for sand capping and drainage and three compressible foundation materials are included to provide a PSDDF user with suitable parameters for these material types. To reduce the difficulty of obtaining the consolidation and desiccation parameters for dredged material, empirical correlations between the required parameters and soil index properties are presented.

Settlement of Dredged and Contaminated Material Placement Areas. I: Theory and Use of Primary Consolidation, Secondary Compression, and Desiccation of Dredged Fill

A 1D nonlinear numerical model, Primary Consolidation, Secondary Compression, and Desiccation of Dredged Fill (PSDDF), is presented to predict the settlement of fine-grained dredged material and/or underlying compressible foundation materials that may be over-, under-, or normally consolidated. The three most important natural processes affecting the long-term settlement and thus service life of dredged material placement areas are primary consolidation, secondary compression, and desiccation. Nonlinear finite-strain consolidation theory is used to predict the settlement due to self-weight and surcharge-induced consolidation. The Cα ∕ Cc concept is used to predict the settlement from secondary compression, and an empirical desiccation model is used to describe the settlement from removal of water from confined dredged material by surface drying. This paper describes the modifications and improvements of PSDDF that present new functions and enhanced numerical efficiency. A companion paper describes the inp...

ITV handbook: technologies & standards

Interactive television (iTV) is an evolutionary merging of digital TV and the internet. iTV technology offers new powerful ways for consumers to interact with content and service providers. In Europe, iTV has gained significant traction during the turn of the century. For example, about 500,000 viewers signed up for SkyDigital's email service during 2000. In another example, Nickelodeon's "Watch Your Own Week" voting application was available to SkyDigital viewers during Oct 22-27 2001. While only 100,000 votes were anticipated for the whole week, this goal was reached within two days; a total of 578,000 votes were recorded for the week. Today, Europe counts tens of millions of iTV consumers.The iTV Handbook is a broad overview of the business and technical issues, and could be used as a textbook for an introductory technical course: it lays out the current thinking on commercially viable uses of iTV, surveys the related technical standards, and describes a broad range of technologies and the relationships among them. A whole chapter is devoted to the big picture of the iTV food chain, and another key chapter is devoted to a survey of media streaming methods. A "file system in the sky" is described which is the broadcasting equivalent of the network file system, and can be used to eliminate the notorious "hot spot" encountered when millions of receivers are trying to access a small set of pages. The book provides many rare insights into the nuts and bolts of the technologies being used. For example, the book presents part of the theoretical foundation for MP3 compression, and describes in detail many popular file formats used to deliver iTV content, including GIF, QuickTime, AVI, and ZIP.

Analysis of Buildings and Structures on Complex Nonuniformly Compressible Foundation Beds

The need to present material derived from geologic-engineering surveys at construction sites in the form of a three-dimensional model is substantiated. It is noted that combined processing of data on drilling, probing, and laboratory tests with results of geophysical studies makes it possible to obtain a three-dimensional picture of the structure of foundation beds. An example is cited for the design and construction of buildings on nonuniformly compressible soils.

Linear and nonlinear models of seismoisolating foundations

AbstractRecurrent formulas are derived to determine stress tensors and displacement vectors for compressible and incompressible plate‐like foundations. A three‐layered plate with an incompressible middle layer is considered as an example of practical significance for seismostable constructions. Nonlinear problems for strip‐seismoisolators from incompressible materials are discussed.

Effect of the Foundation Quality on a Geotextile-Reinforced, Brick-Faced Soil Retaining Wall

This paper describes a study carried out on geotextile-reinforced, brick-faced retaining walls built with different foundation conditions and reinforcement geometry in order to examine the effect of foundation quality. A total of five different foundations were tested in order to investigate if either a good foundation or a large and expensive wall-face footing might be necessary to ensure good performance of rigid-faced walls with short reinforcement layers. The results show that the foundation quality is indeed a very important factor in determining the behaviour of the walls. However, walls built on compressible foundations, with footings three times the width of the wall, show a behaviour similar to walls built on strong foundations (simulated in this study by the base of a steel test tank).

Design of Small, Hard-Shell Overflow Dams on Compressible Foundations

Considering the peculiarities of small hydropower station construction, the province of Hebei, China, has creatively built a series of hard-shell overflow dams on compressible foundations designed to meet the different geographic and geological characteristics of the sites. Structurally, locally collected stones are used as dam filter; then concrete or reinforced concrete is used to form a hard-shell overflow face slab. In upstream seepage control design, natural sealing methods are used to replace the artificial upstream blanket designs, in consideration of the river flow condition of high sediment density and high suspended sediment concentration. Based on the riverbed foundation characteristics and the hydrological properties, synthetic energy dissipation methods are used instead of the usual still plunge pool methods to simplify the dam structure and to reduce the construction cost. This is a theoretical study commissioned by the Hebei Bureau of Water Resources on the design of hard-shell overflow dams that have been constructed on compressible foundations. The major technical problems of constructing hard-shell dams on compressible foundations are (a) dam body stability and face slab structure stress analysis; (b) the influence of the settlement of the foundation and dam body on the face slab and the superstructure; (c) downstream energy dissipation and erosion control measures; and (d) seepage damage control measures of the dam body and foundation.

Calculating unsteady seepage in a pressure gradient in the presence of thin weakly permeable inclusions

A new mathematical model is developed for unsteady seepage in a pressure gradient through a compressible foundation of a gravity dam with an antiseepage curtain. High-accuracy discretization algorithms are developed for the corresponding initial boundary-value problem with a discontinuous solution.

Performance of a geogrid reinforced slope on compressible foundation : Chandra, D; Lay, G Proc 28th Symposium on Engineering Geology and Geotechnical Engineering, Boise, 1–3 April 1992P84–92. Publ Pocatello: Idaho State University, 1992

Performance of a geogrid reinforced slope on compressible foundation : Chandra, D; Lay, G Proc 28th Symposium on Engineering Geology and Geotechnical Engineering, Boise, 1–3 April 1992P84–92. Publ Pocatello: Idaho State University, 1992