Fatigue Properties of the Two Composite Geotextiles

In order to make clear the service life of the two composite geotextiles, their fatigue and dynamic creep properties were tested and compared. The experimental results show that the dynamic creep deformations of adhesive bonded composite geotextiles are lower than those of needle -punched composite geotextiles and the former also have longer fatigue lifetime than the latter.As during the making process, the component parts of adhesive bonded composite geotextiles are not damaged by any factors which in case make their tensile strength higher than those of the needle- punched composite geotextiles. At the end of the paper, a proper explanation was given to this phenomenon.

Influence of Processing Parameters on Properties of Needle-punched Composite Geotextiles

The influence of the processing parameters on the properties of needle-punched composite geotextiles,compounded by polypropylene filament woven-fabrics and nonwoven fabrics is studied by using orthogonal design method. The relationship between tensile strength and peeling strength is discussed. The experimental results are offered as reference.

Comparison of Geotextiles by Aeration Vacuum Rapid Dewatering Technique on Dredged Sludge

In order to accelerate the consolidation of the dredged sludge and look for an effective material for mud-water separation,the study on the comparison of geotextiles is carried on. It is based on the laboratory model test of aeration vacuum rapid mud- water separating( AVMWS) technique and evaluated by the cumulative weight of pumping water,the decrease of moisture content and the stable pumping speed. The results show that woven fabric is the best anti- clogging aeration vacuum material,followed by machine-woven fabric and non-woven fabric is the worst. The analysis has been proposed from two aspects of geotextile weaving technology and aeration vacuum condition.

A STUDY OF THE SPECIMEN SIZE OF STRIP TENSILE TEST FOR NEEDLE-PUNCHED NON-WOVEN GEOTEXTILES

In this paper,the failure features of strip tensile specimen were observed and analysed for need-le-punched non-woven geotextiles.A mechanical model which expresses the relation between thetensile modulus,the strip specimen size,contraction factor and the tensile strength of non-wovenfabric was derived.The theoretical prediction showed that the main factor influencing tensilestrength of non-woven geotextile specimens with different size is the contraction factor of specimenor the specimen aspect ratio(width/length).The larger the aspect ratio,the higher the tensilestrength test value of geotextiles,but the experiments showed that the specimen tensile strength isnot increased with increasing the width of specimen.The reason was discussed and it seemed thatthe deviation could be served as an indication of the degree of imperfectness of the non-wovenstructure.

Processing Methods and Properties of Two Composite Geotextiles

In order to develope new composite geotextiles with good comprehensive properties,the needle-punched composite geotextiles and adhesive bonded composite geotextiles were made in the factory and laboratory separately.The two processing methods were studied and the mechanical and hydraulic properties of the two kinds of products were tested and compared.The experimental resultsshow that the breaking strength of needle-punched composite geotextiles is much lower than that of adhesive bonded composite geotextiles and the latter also have better hydraulic properties than the former which used

Intelligent Tester for Geotextiles Products-Determination of Water Flow Capacity in their Plane

Geotextiles and geotextile-related products Determination of water flowcapacity in their plane has just National standard. But has not a formal instrument at present. There are many kinds of geotextile and also lots of factors influential to the penetration coefficient thereof. The intelligent tester may be involved in testing penetration coefficient under different pressures/gradients resulted in fine repeatability controlled intelligently by microcomputer system.

Investigation on Porosity and In-plane Water Permeability of Nonwoven Geotextiles

Nonwoven geotextiles have been widely used as drains orfilters in many civil engineerings.The hydraulic charac-teristics of geotextiles are the basic function in these ap-plications.The in-plane permeability of nonwoven geo-textiles was discussed in this paper.The results of in-plane permeability coefficient of nonwoven geotextilesfrom measurement were analyzed.

Effect of coir geotextile and geocell on ephemeral gully erosion in the Mollisol region of Northeast China

The unique geomorphological features and farming methods in the Mollisol region of Northeast China increase water catchment flow and aggravate the erosion of ephemeral gully(EG).Vegetation suffers from rain erosion and damage during the growth stage,which brings serious problems to the restoration of grass in the early stage.Therefore,effects of coir geotextile and geocell on EG erosion under four confluence intensities were researched in this study.Results of the simulated water discharge erosion test showed that when the confluence strength was less than 30 L/min,geocell and coir geotextile had a good effect on controlling EG erosion,and sediment yield of geocell and coir geotextile was reduced by 25.95%–37.82%and 73.73%–88.96%,respectively.However,when confluence intensity increased to 40 L/min,protective effect of coir geotextile decreased,and sediment yield rate increased sharply by 189.03%.When confluence intensity increased to 50 L/min,the protective effect of coir geotextile was lost.On the other hand,geocell showed that the greater the flow rate,the better the protective effect.In addition,with the increase in confluence intensity,erosion pattern of coir geotextile developed from sheet erosion to intermittent fall and then to completion of main rill,and the protective effect was gradually weakened.In contrast,the protective effect of EG under geocell was gradually enhanced from the continuous rill to the intermittent rill and finally to the intermittent fall.This study shows that coir geotextile and geocell can prevent EG erosion,and the effect of geocell is better than that of coir geotextile on the surface of EG.

Impact Containment Barriers with Geotextile Tubes

Recently, tragic tailings dam collapses in Brazil have caused deaths and major destruction and the need to develop technologies capable of preventing damage to people and the environment. Brazilian tailings dams are in a situation of uncertainty due to new legislation that even requires decommissioning, an activity that involves many problems and where the risk of failure is the main one. An impact containment structure downstream of these dams can be effective and geotextile tubes, in a new approach, have emerged as an option with advantages in terms of execution, costs and safety. The technology is versatile and can bring many benefits such as the reuse of tailings or filling with low-energy or reused materials. In this research, geotextile tubes were tested as free containment barriers, experiencing impacts in reduced models. The safety factor for the stability of the structure was constructed using an equation which is the ratio between the self-weight of the barrier structure and its coefficient of static friction and the impact pressure, where the data showed an adequate correlation which suggests the viability of mitigating risks.

Laboratory Study of Geotextiles Performance on Reinforced Sandy Soil

This paper presents the results of triaxial tests conducted for the investigation of the influence of geotextiles on stress-strain and volumetric change behaviour of reinforced sandy soil. Tests were carried out on loose sandy soil. The experimental program includes drained compression tests on samples reinforced with different values of both geotextiles layers （Ng） and confining pressure （σ′c）. Two methods of preparation were used： air pluviation （AP） and moist tamping （MT）. Test results show that the geotextiles induce a quasi-linear increase in the stress deviator （q） and volume contraction in the reinforced sand. Method of preparation significantly affects the shear strength; samples prepared by the air pluviation method and mobilized deviator stresses are significantly higher than those prepared by moist tamping method. Geotextiles restrict the dilation of reinforced sandy soil and consequently the contraction increases. The mobilized friction angle increases with increasing number of layers and decreases with increasing initial confining pressure. Samples prepared by moist tamping present mobilized friction angles significantly lower than those prepared by air pluviation method. For samples prepared by the air pluviation method, the secant modulus at ε1=1% and 5% decreases with increasing geotextile layers; those prepared by the moist tamping method, secant modulus at ε1=1% and 5% increases with increasing number of geotextile layer sand confining pressure. From 10% axial strain, secant modulus increases with increasing inclusions of geotextile layers.

Shear strength behavior of geotextile/geomembrane interfaces

This paper aims to study the shear interaction mechanism of one of the critical geosynthetic interfaces,the geotextile/geomembrane, typically used for lined containment facilities such as landfills. A largedirect shear machine is used to carry out 90 geosynthetic interface tests. The test results show a strainsoftening behavior with a very small dilatancy （〈0.5 mm） and nonlinear failure envelopes at a normalstress range of 25e450 kPa. The influences of the micro-level structure of these geosynthetics on themacro-level interface shear behavior are discussed in detail. This study has generated several practicalrecommendations to help professionals to choose what materials are more adequate. From the threegeotextiles tested, the thermally bonded monofilament exhibits the best interface shear strength underhigh normal stress. For low normal stress, however, needle-punched monofilaments are recommended.For the regular textured geomembranes tested, the space between the asperities is an important factor.The closer these asperities are, the better the result achieves. For the irregular textured geomembranestested, the nonwoven geotextiles made of monofilaments produce the largest interface shear strength.

Influence of Polyester Resin Treatment on Jute Fabrics for Geotextile Applications

In this study, jute woven fabrics (1 × 1 plain, twill, zigzag and diamond weave) were manufactured from 100% raw jute yarn. The fabric specimens were treated by 5%, 10%, 15%, 20% and 25% unsaturated polyester resin where styrene monomer used as a solvent and 1% methyl ethyl ketone peroxide (MEKP) was used as initiator. Two bar pressure was applied for complete wetting of the fabric by a Padder and curing was done at 130?C for 10 minutes. The physico-mechanical characteristics of untreated and treated samples were examined and evaluated. It was revealed that moisture content (MC) and water absorbency of the treated specimens were decreased with the increase of resin percentage (%) in the fabrics. MC and water absorbency were maximum decreased up to 50.23% and 60.14% respectively by 25% resin treatment. On the other hand, bending length (BL), flexural rigidity (FR), flexural modulus (FM) and tensile strength (TS) were enhanced with the increase of resin percentage in the fabrics which resulted higher fabric stiffness. The maximum improvement of BL, FR, FM and TS were found to be 6.67%, 56.04%, 10.57% and 18.75% respectively in comparison to untreated sample. Soil degradation tests exhibited that 33.59% TS loss occurred for untreated specimens where only 8.04% loss of TS found for 25% resin treated one. Furthermore, jute based twill, zigzag and diamond fabrics were also treated by 10%, 15%, 20% and 25% resin, then measured their TS and compared with plain fabrics. It was revealed that plain fabrics have superior TS over other fabrics. It was also evident that TS enhanced for all the fabrics after resin treatment and maximum increase found for all the fabrics up to 25% resin treatment.

Design Methods for Geotextile Tubes Application in Dike Construction

The technique of geotextile tubes used to construct dikes for land reclamation has been widely used. The tubes are usually filled with slun＇y of soil, such as sand, silt or clay. The tensile stress developed in the geotextile during filling the tube is the dominant factor for construction of a safe dike. The existing design methods are good for designing sausage shaped tubes and can not be directly applied for designing fiat tubes, which are commonly used in dike construction. This paper presents a procedure that can detenmine the relatiorrship among the tube size, the pumping pressure, the unit weight of the slurry, and the tensile stress developed in the geotextile during the tube filing. When the tubes are piling up to form the dike, the tubes in the bottom will sustain the load from the weight of the upper ones. A procedure is also developed to calculate the changes of the mechanical and geometrical behavior of the tubes under the load with a similar method. All these approaches have been programmed, which can help dike designers to select the suitable geotextile and determine the profile of the dike.

Novel experimental techniques to assess the time-dependent deformations of geosynthetics under soil confinement

A new experimental approach to assess the impact of soil confinement on the long-term behavior of geosynthetics is presented in this paper.The experimental technique described herein includes a novel laboratory apparatus and the use of different types of tests that allow generation of experimental data suitable for evaluation of the time-dependent behavior of geosynthetics under soil confinement.The soil-geosynthetic interaction equipment involves a rigid box capable of accommodating a cubic soil mass under plane strain conditions.A geosynthetic specimen placed horizontally at the mid-height of the soil mass is subjected to sustained vertical pressures that,in turn,induce reinforcement axial loads applied from the soil to the geosynthetic.Unlike previously reported studies on geosynthetic behavior under soil confinement,the equipment was found to be particularly versatile.With minor setup modifications,not only interaction tests but also in-isolation geosynthetic stress relaxation tests and soil-only tests under a constant strain rate can be conducted using the same device.Also,the time histories of the reinforcement loads and corresponding strains are generated throughout the test.Results from typical tests conducted using sand and a polypropylene woven geotextile are presented to illustrate the proposed experimental approach.The testing procedure was found to provide adequate measurements during tests,including good repeatability of test results.The soilegeosynthetic interaction tests were found to lead to increasing geotextile strains with time and decreasing reinforcement tension with time.The test results highlighted the importance of measuring not only the time history of displacements but also that of reinforcement loads during testing.The approach of using different types of tests to analyze the soilegeosynthetic interaction behavior is an innovation that provides relevant insight into the impact of soil confinement on the time-dependent deformations of geosynthetics.

Reinforcement of Soft Foundation with Geotextile and Observation for Sea Dike Project of Zhapu Port

The design method of reinforcement of soft foundation with geotextile for the sea dike of the Zhapu Port is discussed in this paper. The prototype behaviours such as pore water pressure, settlement and so on were observed. The degree of consolidation is found out from observed pore water pressure and observed settlement respectively, then the strength increment of soil is calculated and compared with that obtained from vane shear tests. For the use of observed pore water pressure, the consolidation coefficient of soil is deduced approximately with a method named experimental exponential interpolation. The degree of consolidation of the ground is deduced theoretically from the dissipation of pore water pressure. Besides, the logarithmic curve and hyperbola are used to fit the observed time-settlement curve, and the degree of consolidation of soil is obtained according to the definition of the consolidation degree. After preliminary verification with observed prototype data, the method to reinforce the low dike with geotextile is considered to be simple and rational, and it can also reduce the construction cost.

Impact of repeated loading on mechanical response of a reinforced sand

Pavements constructed over loosely compacted subgrades may not possess adequate California bearing ratio (CBR) to meet the requirements of pavement design codes,which may lead to a thicker pavement design for addressing the required strength.Geosynthetics have been proven to be effective for mitigating the adverse mechanical behaviors of weak soils as integrated constituents of base and sub-base layers in road construction.This study investigated the behaviors of unreinforced and reinforced sand with nonwoven geotextile using repeated CBR loading test (followed by unloading and reloading).The depth and number of geotextile reinforcement layers,as well as the compaction ratio of the soil above and below the reinforcement layer(s) and the compaction ratio of the sand bed,were set as variables in this context.Geotextile layers were placed at upper thickness ratios of 0.3,0.6 and 0.9 and the lower thickness ratio of 0.3.The compaction ratios of the upper layer and the sand bed varied between 85% and 97% to simulate a dense layer on a medium dense sand bed for all unreinforced and reinforced testing scenarios.Repeated CBR loading tests were conducted to the target loads of 100 kgf,150 kgf,200 kgf and 400 kgf,respectively (1 kgf=9.8 N).The results indicated that placing one layer of reinforcement with an upper thickness ratio of 0.3 and compacting the soil above the reinforcement to compaction ratio of 97% significantly reduced the penetration of the CBR piston for all target repeated load levels.However,using two layers of reinforcement sandwiched between two dense soil layers with a compaction ratio of 97% with upper and lower thickness ratios of 0.3 resulted in the lowest penetration.

In-depth improvement of soil at the base of roads on taliks

The article presents a new technological solution to improve the safety of embankment bases on taliks during construction periods. The use of geotextile-sleeved sand columns and geogrids on low-temperature permafrost is investigated. The correlations between mechanical and temperature processes under this in-depth base improvement method are calculated.

Experimental Study on Permeability Characteristics of Geotubes for Seepage Analysis on Safety Assessment of Dams

Geotubes are heterogeneous structures composed of filling sand and bag material,and its pemeability characteristics are different from that of flling sand.The uncertainty of geotubes permeability characteristics results in the failure of seepage analysis of geotube dams,which restricts the safety assessment of the dams.As the basis of the study on the seepage mechanism of the geotubes,the influence of particle grading on pemeability cofficient of flling sand and sand covered with geotextiles were explored by the pemmeability tests of flling sand with different particle grading under the condition of sand covered with or without geotextiles.And the infuence of geotextiles on the permeability coefficient was analyzed by comparing permeability coefficient of sand covered with and without geotextiles.The test results show that the influence of single particle size content on permeability coe ficient is consistent under the condition of sand covered with and without geotextiles.The content of powder,fine,medium and coarse particles is linearly related to their respective permeability cofficients.And the content of powder,fine,medium particles is negatively correlated with their permeability coefficients,while the content of coarse particles is positively correlated with the permeability coefficient.But the pemeability coefficient of sand covered with geotextiles is smaller than that of flling sand under the same conditions.Finally,the parameter d2 50 Cc/Cu was selected as a variable representing the particle grading to fit the empirical formula of permeability coefficient of flling sand and sand covered with geotextiles.

Drainage Bed:A Natural System for WTP Sludge Dewatering and Drying with Different Coagulant Chemicals in Tropical Countries

This study seeks to evaluate the mechanisms for dewatering sludge from Water Treatment Plants (WTP) in a natural system that uses nonwoven polyester geotextile blankets named Drainage Bed (DB). Dewatering mechanisms are divided into two stages: Drainage and Drying Phases. For the Drainage Phase, the results showed that the solids content of the Aluminum Sulfate sludge reached 8.9% to 18.3% and the PACl sludge 1.8% to 6.5%, the volume reduction on this phase exceeding 50% and 74%, respectively. The final solids content, after the Drying Phase, was greater than 28%, reaching 90%. In the Drainage Phase the lower the Surface Application Rate—SAR [kg/m2] is, the greater the drainage flow will be. In the Drying Phase, moisture and insolation were key factors in drying sludge. Thus, the Drying Phase in the DB takes special attention for being virtually nonexistent in dewatering technologies in a closed system (confined) without exposure to solar energy. The use of the DB as a natural system for dewatering WTP sludge in tropical countries proved to be a promising alternative, because of its efficient removal of water from sludge coupled with operational simplicity and low costs, provided there is area available.

Effects of geotextile envelope and perforations on the performance of corrugated drain pipes

Subsurface drainage is an important agriculture drainage measure.It is primary to select suitable drain pipes and envelopes for efficient subsurface drainage.And now,corrugated drains and geotextile envelopes are widely used.However,the effects of geotextile envelopes and perforations on the drainage of corrugated drains are not well understood.This study conducted a series of sand tank experiments of steady-state flow with or without geotextile envelopes and with different perforation patterns.The drainage flow and the profile head distributions were analyzed and compared.Furthermore,the applicability of theoretical formulas,which are used to calculate effective radius considering the resistance of different perforation patterns,was evaluated.Results showed that the geotextile envelope weakened the effect of perforations on streamlines,thereby causing the value of effective radiuses to be close to that of the actual radius.The drainage flow of the drain with a geotextile envelope was six times that of the bare drain.The relationship between drainage flow and opening area could be described by inverse proportional function.Meanwhile,the drainage flow was affected by the perforation arrangement.Drain with small longitudinal perforation spacing had a drainage flow of approximately 15%larger than that with wider longitudinal perforation spacing.The bottom perforations drained out first and most,and the drainage flow of the drain opened at the bottom could be 11%higher than that at the top.Low-efficiency perforations cause higher head loss near the pipe wall.Existing formulas of entrance resistance were not suitable for geotextile-wrapped corrugated drains,the effect of geotextile envelope and orifice entrance loss at perforations should be considered.