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Geotextiles are widely used in coastal revetment work as a separator and a filter between the base soil and the armor stones. In order for them to function properly as hydraulic filters in coastal revetments, they must first be able to survive the construction process. The tensile strength and mass of geotextiles are often specified to meet the survivability requirements. But these parameters do not necessarily reflect the puncture resistance characteristics of the geotextiles. Hence, there is a need to understand the performance of these geotextiles in meeting the survivability requirements and to quantify the puncture resistance of geotextiles more confidently. An extensive field drop test was recently completed in Singapore to study the puncture resistance of geotextiles. This field test comprised 784 controlled drop tests using a standardized drop block released from heights ranging from 0.5 m to 2.5 m. Five different geotextiles (two woven and three nonwoven) were tested, including three new double layer geotextiles. The drop tests were conducted for geotextiles laid over different soil conditions, with varying thickness of secondary armor stones. Both horizontal and sloping grounds were used. The extent of damage on the geotextiles was assessed based on statistical interpretation of a large number of drop tests, taking into account the number and size of the punctures. The field test seeks to provide some standardization in conducting field drop tests and evaluating the puncture resistance of geotextiles in the field. Results of the field test were compared with standard index tests currently in use. It was found that existing index tests do not adequately reflect the geotextiles' ability to resist puncture and tear. However, results suggest that the puncture resistance of the geotextile can be evaluated reliably by the Energy Level of the geotextile.

Biomechanical performance studies were undertaken for powder-free, latex and nitrile examination gloves. Using standardized tests, examination glove performance was judged by measuring glove thickness, glove puncture force, glove tape adhesion force, glove donning force, glove stiffness, and immediate unrecovered stretch. Even though the nitrile examination gloves were thinner than the latex examination gloves, they exhibited a greater puncture resistance. In addition, tape adherence to the N-Dex nitrile glove was the lowest. Moreover, measurements of the handling characteristics of the nitrile examination gloves demonstrated that they are an acceptable alternative to latex examination gloves. While these biomechanical studies demonstrate the superiority of the nitrile examination gloves, clinical glove evaluation is still needed to determine their performance in the health care setting.

The National Fire Protection Association has developed standards for glove puncture resistance using a metal puncture probe. Biomechanical performance studies have demonstrated that glove puncture resistance to the probe is significantly greater than that of the hypodermic needle, suggesting that these standards have no clinical relevance. These standards give a false sense of security to health care personnel and sanction the production and use of gloves that give inadequate protection. The result is potentially harmful for medical personnel.

This paper focuses on the development of a theoretical model for predicting the behavior of laterally restrained, fiber-reinforced concrete bridge decks. Based on observations of the failure modes in experimental testing and a review of models used for the punching failure of reinforced concrete slabs, a rational model is developed. The assumptions and equations used in the model development are presented along with the solution algorithm. The theoretical model is checked through comparison with several half-scale and full-scale tests on laboratory bridge decks. The results of the experimental programs are recorded elsewhere and listed in the references.

Flexural and punching failure experiments were performed on flat slabs by controlling the vertical displacement under the column. This allows the monitoring of the descending branch of the load-displacement curve and establishes that flexural failure is characterized by a smooth decrease of the load-carrying capacity, whereas punching failure exhibits a sudden reduction of this capacity. It is shown both experimentally and with force equilibrium that one condition for punching failure that occurs is that the internal strength of the punching cone is larger than the punching strength itself. The punching load was reached for a punching crack inclination of approximately 30 deg (0.5 rad) to the middle plane of the slab. By increasing this inclination, the flexural failure load was approached and the sudden decrease of the load-carrying capacity was reduced. A smooth transition between punching and flexural failure, which is controlled by the punching crack inclination, is revealed, and an interaction formula is proposed.

Slab-column connections were tested under combinations of gravity and lateral loads to investigate the effect of using high-strength concrete slab on the structural behavior of the slab-column connections. The variables selected for this study are the strength of concrete slab, the flexural steel reinforcement ratio, and the moment to shear ratio. As the concrete slab strength increases from 35 MPa to 75 MPa, the shear strength increases by 7% and 15% for loading cases of zero and high moment-shear ratio, respectively. However, the current design codes provisions for interior connections have greatly reduced the factor of safety regarding the punching shear strength of high-strength concrete slabs. The use of high-strength slab has a significant effect on the load-deflection characteristics for specimens subjected to high-moment. The ultimate deflection increases and the failure mode becomes less sudden and more gradual, if high-strength concrete slab is used. The first yielding for specimens constructed with high-strength concrete slab occurs at loads considerably lower than those for specimens constructed with normal-strength concrete. The radius of yielding significantly increases for specimens constructed with high-strength concrete slab; therefore, the steel reinforcement is utilized better and a much more desirable steel stress distribution is produced in the area around the column by the use of high-strength slab. In the meantime, connection displacement and rotation ductility increases by 75% for specimens with high-strength concrete slabs under high moment. Therefore, the use of high-strength concrete slabs can be justified economically when good ductility and higher levels of absorbed energy of slab-column connections are required under high moment-shear ratios. On the other hand, the use of high-strength concrete slabs for slab-column connection subjected to gravity loads only is not recommended because of the small increase of the punching shear capacity of the connection compared with the high cost of using high-strength concrete.

The paper presents the results of an investigation about the behavior of reinforced concrete flat slabs made with high strength concrete, steel fibers and ordinary shear reinforcement. We tested twelve flat slabs made with different combinations of high strength concrete, ordinary strength concrete, shear reinforcement and steel fiber volume fraction (0%, 0.75% and 1.5%). The square-shaped slabs were designed to represent the slab-column connection in an interior column. A significant increase in the punching shear strength was observed, due to the use of high strength concrete and the addition of steel fibers. The combination of high strength concrete with 1.5% fiber volume fraction and shear reinforcement provided twice the punching shear resistance of an ordinary strength concrete slab without shear reinforcement and without fibers. Fiber addition is believed to be responsible for an increase of approximately 50% in the resistance and also for an increase in ductility. Comparisons with theoretical code provisions, including CEB/90, ACI-318/89 and Eurocode 2, are presented.

An experimental investigation was carried out on shear enhancement of high-strength concrete plates for six high-strength concrete slabs to study punching shear capacity and shear enhancement. Five types of different shear reinforcement, namely single bend, U-stirrup, double bend, shear-stud, and T-headed shear reinforcement, were tested and evaluated. The emphasis is placed on the evaluation of their contribution to punching shear capacity of high-strength concrete plates. Structural behaviors were evaluated in terms of overall load-deflection response, ultimate loading capacity, postultimate loading capacity, ductility and energy absorption. Failure patterns and strain distribution were also discussed.

Tests were conducted under a concentrated monotonically increasing static wheel load on 1/6.6-scale physical models of three different types of noncomposite deck structure: (1) the entire deck supported on four steel girders; (2) an isolated deck slab region with a width equal to 1/3 of the bridge span; and (3) a 102-mm-wide transverse “beam” deck strip, both simply supported on two opposite edges on adjacent girders. Three reinforcing arrangements for the noncomposite concrete deck are studied: (1) orthotropic steel reinforcement (AASHTO); (2) isotropic steel reinforcement ( Ontario 1983); and (3) “isotropic-0.2%” minimum steel reinforcement. Flexural steel and concrete strain measurements in the “beam” deck strip models are compared with those in the models of the entire bridge deck where combined membrane compression and bending is present. Depending on the degree of the lateral and/or rotational edge restraint of the deck specimens, the ultimate load-carrying capacity of the models of the entire bridg...

An analytical expression developed to compute the punching strength of reinforced concrete is derived from results obtained with numerical simulation of the failure phenomenon. This simulation reveals that punching strength can be computed by integrating the vertical tensile stresses (assumed constant) around the punching crack (assumed to be a truncated cone in shape). Punching strength is also expressed in terms of the tensile strength of concrete, percentageof flexural reinforcement, slab thickness, and radius of punching crack initiation. The effects of reinforcement are taken into account in a unified approach by adding the vertical tensile resistance of each type of reinforcement. Punching strength computed with the developed analytical expression enables prediction of the experimental punching loads of slabs with different sizes, concrete strengths, and percentages of reinforcement, reinforced with ring reinforcement, orthogonal reinforcing bars, stirrups, shearhead, and prestressing tendons.

The puncturing of geomembranes by stones is unfortunately not uncommon. In order to prevent its occurrence, various geosynthetics have been used as protection materials. Needle punched nonwoven geotextiles (of various unit weights), geonet drainage composites, and geosynthetic clay liners have been used, and all are evaluated in this laboratory puncture study. Results from three standardized puncture test methods (tapered, pin, and pyramid shaped end probes) are compared to one another. The results show that all geomembranes are susceptible to puncture, with increasing thickness providing some, but limited, improvement. Geotextiles clearly show improved puncture protection, and the improvement is in linear proportion to their increasing unit weights. Geonet drainage composites also show improvement essentially in proportion to the unit weights of the geotextiles affixed to the surfaces of the geonet core. Geosynthetic clay liners also provide protection, again in proportion to the unit weight of the associated geotextiles, particularly when the bentonite is hydrated.

The primary objective of this experimental study was to determine whether addition of steel fibers to the concrete mix could significantly increase the punching shear strength of reinforced concrete slabs. Thirteen slab specimens and their companion cylinder specimens were tested. Fiber concentrations in the slabs ranged from 0 to 6.4 percent by weight of concrete. Test results of this study indicate that the addition of steel fibers to the concrete mix does significantly enhance the punching shear strength of slabs. A modification of the standard code design equation for shear punching strength of slabs is suggested to reflect the strength increase produced by the fibers. The tests also provided information on the shape and inclination of the fracture surface, and indicated that only a small, shallow region of the slab in the vicinity of the slab-column intersection is highly stressed in tension before rupture. This means that punching shear failure occurs in a progressive manner.

The transfer of shearing forces and moments between concrete flat slabs and columns can produce brittle punching failure. Slab-column connections must satisfy adequate strength against punching failure. In seismic zones, the connections are expected to undergo deformations into the inelastic range and, hence, it is necesary to design connections with adequate strength and ductility. In addition, the connections must be able to undergo a specified limit of interstory drift without punching failure. The ductility and drift requirements that must be adhered to in design are discussed. Tests reported in the literature show that the strength under cyclic moment transfer is less than the strength under monotonic loading. For an earthquake-resistant structure, the design must be based on the strength under cyclic loading. Test results are reviewed and discussed. As an application, a hypothetical structure is designed according to American Concrete Institute (ACI) Building Code (ACI 318-89). The structure is subjected to the 1940 Elcentro ground motion, and time-history dynamic analysis is performed. The results show that to obtain adequate strength, drift capacity, and ductile behavior of a slab-column connection without shear reinforcement, it is necessary in most cases to increase substantially the slab thickness in the connection region beyond the minimum thickness required to control deflections by providing shear capitals. The disadvantages of shear captials can be avoided by using shear reinforcement.

The effect of superimposed slab loading on the behavior of exterior slab-column connections was studied by testing 2-bay slab-column subassemblies. Each subassembly consisted of an interior and two exterior connections. Three identical slab-column subassemblies were subjected to the same cyclic lateral-displacement history while each supported a different superimposed slab load. The tests show that increased slab load substantially reduces the lateral drift capacity of the connections. A limiting shear stress is suggested to insure adequate drift capacity for exterior slab-connectiions. A rational method to calculate the moment capacity of exterior connections is developed. The test results are compared with present ACI 318-83 Building Code provisions and ACI Committee 352's recommendations for design of slab-column connections.

Punching tests on 12 restrained reinforced concrete slabs are re­ ported in this paper. The slab panels were supported and restrained on all jour sides by edge beams. The influence of the degree of edge restraint, percentage of steel reinforcement, and span-depth ratio of the slabs on the structural behavior and punching shear capacity of the slabs was investigated. The punching shear strengths observ.ed were much higher than those predicted by Johnson's yield-line the­ ory, BS 8110, and ACI 318. The enhanced punching shear capacity was a result of compressive membrane action caused by restraining action at the slab boundaries.

Seventeen reinforced concrete slabs were tested to investigate the deformation and strength characteristics of punching shear failure of high-strength concrete slabs. The tested specimens had different slab depths and reinforcement ratios varying between 0.49 and 2.33 percent. Test results revealed that high-strength concrete slabs exhibit a more brittle failure than normal strength concrete. Experimental results indicated that as the level of reinforcement is increased the punching strength of the slabs also in increased. It was found that using the cubic root of the concrete compressive strength to predict the punching resistances of the concrete slabs generally yields better results than the square root expression used in North American codes.

SHIPPERS OF extremely hazardous chemicals, such as chlorine and anhydrous ammonia, will have to replace their existing fleet of rail tank cars with a new generation of more impact-resistant cars, according to a newly proposed federal plan to improve freight rail safety. The rule, proposed on April 1 by the Department of Transportation’s Federal Railroad Administration (FRA), will require tank cars that carry commodities posing poison inhalation hazards be constructed to resist puncture at speeds of 25 mph for side impacts and 30 mph for head-on collisions—more than double the puncture resistance speeds for existing tank cars. The performance-based standard will increase by 500% on average the amount of energy the tank cars are designed to absorb during an accident without penetration or rupture, according to FRA. “When the opportunity to make major advances in safety is within our reach, we should not settle for incremental measures,” FRA Administrator Joseph H. Boardman says. ...

Puncture of protective clothing by medical needles is a major concern for a number of professional groups. This is particularly true since it has been shown that the protection level of protective gloves measured using the current puncture resistance standards is not relevant when dealing with medical needles. This paper proposes a step-by-step analysis of the puncture mechanism of membranes by medical needles. It investigates also the influence on the puncture force of various characteristics of medical needles, including the needle diameter, number of facets, and facet angle, for a number of materials relevant to protective gloves. It is observed that the effect of these parameters is sometimes very dependent on the type of material punctured. Tests also reveal that the variation in the measured puncture force for mass-produced three-facet medical needles can be associated with the variation of one of the needle dimensions, i.e., the outer diameter at the transition between the facets. Finally, a study of the effect of needle reuse in successive trials shows that cutting-edge wear is much more extensive with reinforced materials. This justifies the need to use needles only once for measuring the puncture resistance of protective clothing materials.

The paper presents a design method to predict the punching strength and deflection of flat plates at interior columns. Failure is assumed to occur when the compression zone of the slab in the vicin ...

Extensive tests presented earlier have establidhed the effectiveness of stud-shear reinforcement in increasing the punching-shear strength and ductility of slab-column connections transfering axial force V and bending moment M. The shear reinforcement is composed of vertical rods mechanically anchored at their top and bottom ends. This paper presents rules to design and detail stud-shear reinforcement in accordance with the 1989 ACI Building Code (ACI 318-89). Three numerical examples illustrate the design of shear studs and their distribution in slabs in the vicinity of interior, edge, and corner columns transferring V and M. Because of effective anchorage, design rules that reduce the amount of shear reinforcement are suggested and applied. Rules for the design according to the Canadian standard CAN3-A23.3-M84 are also given.

The results of an experimental investigation of the punching shesr strength of reinforced concrete slabs with varying span-depth ratios are summarized. Ten axisymmetric slabs were tested. The slab thickness was kept constant while the support diameter was varied to produce different span-depth ratios. The punching shear strength was found to significantly increase as the span-depth ratios decreased below 6. Maximum test strengths were nearly 5 times greater than the 1983 ACI Building Code predicted strengths. The higher strengths were a result of smaller span-depth ratios, in-plane compressive forces caused by restraining action at the supports, and excellent anchorage provided for the shear reinforcement.

The background theory and the punching shear design provisions contained in the New Australian Standard for Concrete Strucures, AS 3600-1988 are described. These design provisions are not only simpler to use than those in ACI 318-83 but also cover situations that are not readily handled by the ACI Building Code. The Australian design method is illustrated by an example. The correlation of the design equations with test data is also presented. It is believed that the Australian method could serve as a useful alternative to the ACI Building Code provisions.

Tests on 4 specimens of a flat-plate floor in the vicinity of an edge column are reported. The purpose of the tests was to study the influence of a spandrel beam and closed ties on the failure strength of the slab in the vicinity of an edge column. The effect of concentration of slab steel in the region near the column is also examined. The 3 specimens with no spandrel beam failed due to the combined effect of moment and shear transferred by the slab to the column. The presence of the spandrel beam effectively prevented punching shear failure of the other specimen. The test results are compared with the provision of the ACI and the Australian codes.

This paper reviews recent research and code provisions on punching shear capacity and its relation to concrete strength. It presents the results of an experimental investigation relating punching shear to concrete strength and steel ratio. The paper concludes that shear capacity is proportional to the cube root of concrete strength and steel ratio and that the ACI-CSA code provisions should be reviewed.

The aim of this work is to investigate the intrinsic parameters that control the puncture resistance of materials used in protective clothing. The effect of various probe geometries and sample holder sizes on puncture tests results were investigated. Medical needles of different diameters and tip angles were also used as puncture probes. Various available commercial rubbers used in protective gloves were characterized. The findings of this study will be useful for recommendations for standard test method protocols to characterize the puncture resistance of protective clothing materials. When cylindrical probes with flat and rounded tip geometries are used, material puncture occurs when the strain reaches one material failure value independent of tip geometry. The failure strain is also independent of sample thickness, probe tip diameter, and the sample holder size. The results demonstrated that the tip angle of conical probes has a dramatic effect on puncture test results. The material puncture resistance obtained with conical probes with different tip angles having a tip diameter d1 and a rod diameter d2 can be interpolated from the corresponding values obtained with cylindrical probes having the same d1 and d2 diameters. On the other hand, cylindrical probes provide a more straightforward characterization of puncture and also eliminate the complex effect of conical probe-tip geometry. Test results with medical needles showed that the puncturing mechanism is different from that of conical and cylindrical probes. Puncture by medical needles involves cutting and fracture energy, whereas puncture by conical and cylindrical probes relates to failure strain.

Objective The aim of the current study was to assess the puncture resistance and stiffness of nitrile and latex dental examination gloves. Methods Puncture resistance was measured by employing an adapted version of ASTM F1342-91 using both a 316 stainless steel puncture probe (0.8 mm diameter) and a dental injection needle (0.45 mm diameter) interfaced to a tensile testing apparatus. Glove specimens (12 cm length, 1.5 cm breadth) were removed for modulus (M100) evaluation by assessing the force required to elongate the specimen to 100% of the original length. Glove samples were also aged to investigate whether puncture resistance and M100 values varied with aging at 70°C for 7 days in an air-circulating oven. Results The nitrile glove types were assessed to have significantly higher puncture resistance compared with the latex glove type when the steel puncture probe was the pentrometer when using the one way analysis of variance (ANOVA) at the 95% significance level. Interestingly the puncture resistance for the latex glove type was significantly higher (p < 0.001) when a dental injection needle was used as the pentrometer compared with the nitrile glove types. The M100 values were significantly higher for the nitrile glove types for which the stiffness increased when the gloves were aged (p < 0.001). Conclusions The higher stiffness values resulted in increased puncture resistance when the nitrile glove specimens were aged irrespective of the pentrometer type. However, the ability of latex to re-seal itself on puncture may be beneficial when considering the protection potential of each glove type against breaches in cross infection. For clinicians that have experienced an adverse reaction to natural latex gloves, the results of the current study indicate that nitrile gloves are available at reasonable cost and offer the clinician comparable resistance to puncture with latex gloves.

Objective To investigate the puncture resistance of a recently introduced non-latex, nitrile dental glove in comparison with a latex glove worn during routine clinical dental procedures. Setting Dentists in general dental practice working within the UK during 1999. Subjects and methods 2,020 gloves worn by five general dental practitioners were examined for punctures following standard clinical use by a water inflation method. Procedures undertaken during glove usage and length of time worn were recorded. Results Following clinical use, 1.9% of the latex gloves and 5.3% of the nitrile gloves had punctures, a statistically significant difference (P < 0.0001). The puncture resistance of the nitrile gloves was superior to the puncture resistance of previously tested worn non-latex (vinyl) gloves. There was no evidence of a statistically significant difference between operators for the percentage or incidence of punctured gloves (P = 0.787) after correcting for glove type. No statistically significant difference was noted between incidence of puncture in the control, unused gloves (n = 200 for each type) and the gloves examined following clinical use (P = 0.907 for nitrile, P = 0.613 for latex). Conclusion No increase in the number of punctures was noted following clinical use for either glove type. This could be considered to indicate good puncture resistance of the gloves tested in clinical use.

This paper describes various uses of high-performance waterproofing systems based on thermoplastic polymeric membranes (TPMs), particularly as they have been employed in tunnels in Switzerland and Austria. TPM linings are characterized by superior puncture resistance, exceptionally low permeability, high chemical resistance, high tensile strength, and excellent elongation properties. Applications of TPM waterproofing systems in both mined and “cut-and-cover” tunnels are presented.

Development of the banded radial tire is discussed. A major contribution of this tire design is a reliable run-flat capability over distances exceeding 160 km (100 mi). Experimental tire designs and materials are considered; a brief theoretical discussion of the mechanics of operation is given based on initial two-dimensional studies and later on more complete finite element modeling. Results of laboratory tests for cornering, rolling resistance, and braking are presented. Low rolling resistance, good cornering and braking properties, and low tread wear rate along with good puncture resistance are among the advantages of the banded radial tire designs.

Both the standards developed by the International Atomic Energy Agency (IAEA) and those contained in the U. S. federal regulations [1] stipulate that transport packagings containing large quantities of radioactive material, such as spent fuel from a nuclear power reactor or waste by-products from nuclear weapons programs, should be designed to resist a sequence of impact, puncture, fire, and water immersion conditions without harmful release of contents. A recent paper [2] has offered a perspective on the design of such packagings relative to the impact event - a 30-foot (9 m) drop onto an essentially unyielding target. In that paper, it was shown that modern tools of computational mechanics, incorporating elastic-plastic material response and finite strain kinematic descriptions, could be used efficiently for the iterative design of a monolithic steel containment system, including models for bolted closures, shear keys, and seals.

A theoretical solution for the punching shear strength of a concrete slab is presented. The problem is treated as a three-dimensional axisymmetrical one, the material being assumed to be rigid-plastic. A failure criterion for the concrete is suggested, in which a second-degree parabola is used for a Coulomb-Mohr yield envelope. By establishing the virtual work equation, an upper-bound solution is obtained, which is simpler than the well-known Braestrup-Nielsen solution. It can also give the ultimate punching shearing load when the punch angle is smaller than the angle of friction of concrete. Simplified expressions for the ultimate strength of a concrete slab in punching shear with different degrees of simplification are also suggested for practical use. The normal, shearing, and principal stresses along the failure surface are also explored.

Synopsis It has been found in three tests that in-plane biaxial tensile strains up to 0·0017 cause no reduction in the strength in punching shear of a reinforced concrete slab 90 mm thick. The test results are compared with the predictions of the recent Bridge Code (BS 5400) and of plastic theory.

Seed coat puncture resistance of 42 cultivars of common and durum wheat, oats, barley and rapeseed were measured by puncture tests believed to approximate seed penetration by weevils infesting stored grain. All seven species of crops, several cultivars, and germ and endosperm parts of the seed within the same cultivar varied significantly [Formula: see text] in puncture resistance of seeds when their moisture contents were m equilibrium at 0% and 70% RH. Dry durum wheat (cv. Wakooma) showed the highest puncture resistance, moist rapeseed (cv. Torch) the lowest. The mean puncture resistance of the endosperm coat of moist crop cultivars ranged from 2,074 to 2,456 g for common wheat; 3,316 to 4,131 g for durum wheat; 1,145 to 1,404 g for oats; 1,321 to 1,861 g for barley; and 184 to 222 g for rapeseed. These differences m seed coat strength suggest that it may be one of the sources governing susceptibility to insect damage of stored grain. Thus, the drier the seed, the greater would be the difficulty for an insect to penetrate the seed coat.

The punching shear strength of restrained concrete slabs is investigated. A rational idealized model of a restrained slab at punching failure is developed. This model is an extension of one previously developed by Kinnunen and Nylander for simply supported slabs. The influence of boundary restraints on punching load is demonstrated and the model is shown to yield accurate estimates of the punching strength of slabs with known boundary restraints. An empirical factor, termed the restraint factor, is introduced to estimate the influence of boundary restraints and can be used in the design of slabs for which the actual restraints are not exactly known. The restraint factors for a number of restrained slab systems are reported.

This report is concerned with laboratory equipment development, laboratory testing, and field investigations of a water seepage barrier consisting of plastic-reinforced asphalt. Three testing methods were utilized and evaluated in the asphalt-plastic-asphalt-chip-coated (APAC) membrane investigation. The first test method evaluated the hydrostatic puncture resistance of an asphalt-polyethylene combination. This test confirmed the hypothesis that the asphalt effectively increases the puncture resistance of the APAC membrane over that of plain polyethylene. The second test investigated the slope stability of a protective APAC chip seal. It was found that a typical 3/8-in. (9.5-mm) cover aggregate remained stable on constructed slopes of 3:1 and 4:1 and also remained stable on a 2:1 slope up to a surface temperature of 122°F (50°C). The third test method evaluated adhesive materials and determined the best suited adhesive for sealing polyethylene overlaps. Subsequent field investigations resulted in equipment development that increased construction efficiency in the installation of the APAC membrane.

Introduction The use of a fabric as a separating layer between a soft subgrade and granular fill, for access roads, working platforms, vehicle standing areas, etc., was one of the first uses of geotextiles in ground engineering and is probably still commercially the most important. Al-though there have been many studies of such a form of construction (e.g. see Ruddock 1977 and several papers to the International Conference on Soil Reinforcement, Paris, 1979) design methods are still largely empirical and it is often difficult to calculate the balance of costs and benefits of using fabrics in this way. A research programme has been started at Oxford University to investigate the problem by means of model tests and computer analyses. The study is mainly concerned with the reinforcing effect of the material, rather than its performance as a filter, particularly in view of the recent introduction of high-strength, high-modulus mesh or grid structures for soil reinforcement. As a preliminary stage a series of simple two-dimensional tests have been performed at approximately 1/l0th scale. Granular fill, with or without reinforcement, was spread over a soft subgrade, represented by foam rubber, and deflections due to a surface strip loading determined. Several different reinforcing materials were used, including smooth sheet material as well as various mesh or grid structures, and the effects of varying fill particle size, fill thickness, reinforcement stiffness and subgrade stiffness investigated. It is appreciated that foam rubber is not an accurate substitute for soft clay, and the tests deliberately

In the development of improved compounds for products such as tires, inner tubes, conveyer belts, and hose, the need was felt of a quick and accurate test which would approximate the puncturing conditions these goods might receive in service. For such a test an apparatus was developed which provides for a puncturing pin to be pulled through the rubber sample, the pulling force being supplied by a vertical Scott tensile tester. The adaptation to the Scott machine (Fig. 1) eliminates the necessity of additional load-recording and extension-pulling apparatus. Construction The test apparatus, of which three views are shown in Fig. 2, is composed of two sections. The top section is a hollow tube through which the puncturing pin (Fig. 3A) travels downward in puncturing the sample (Fig. 3B), which is gripped firmly at the periphery between an internal shoulder on the tube and a sleeve (Fig. 3C) within a threaded cap (Fig. 3D) which screws on to the tube. Distortion of the test piece, while the screw cap is being tightened, is prevented by the inner sleeve which presses vertically against the specimen while the turning action is taken up by slippage between the sleeve and the cap. A horizontal pin is attached to the vertical puncturing pin to provide means for attaching the bottom tube section which pulls the pin downward. The hollow tube of the top section is slotted to allow vertical movement of this horizontal pin.

A series of economical and flexible fabrics were prepared using high-strength polyester yarns with different fabric structures, weft density and number of layers. The effect of these factors on quasi-static puncture resistance was comparatively studied. The failure mode of the fabrics was analyzed with SEM photographs. Findings indicate that the structure and the weft density affected the quasi-static puncture resistance property of the fabrics, the plain fabrics had better puncture resistance property than twill and satin fabrics. The max puncture force and puncture energy of the plain fabrics with 160 yarn/10 cm reached the max values which were 107.43 N and 0.44 J, respectively. The number of layers had a linear relationship to quasi-static puncture resistance. The contact pressure and friction of the probe against the fibers were the main hindrance during the quasi-static puncture process and the breakage of the fibers during the penetration was caused by the bend and tensile deformation. Keywords: High-strength polyester fabrics, Fabric structure, Multiple-layer fabrics, Quasi-static puncture resistance