Pullout Resistances Research Articles

Interaction Between Hexagonal Wire Reinforcement and Rubber Tire Chips with and without Sand Mixture

Abstract The interaction between tire chips with and without sand mixtures and the hexagonal wire reinforcement, as well as the strength characteristics of mix, were investigated by in-soil pullout tests and large-scale direct shear tests. Rubber tire chips with and without sand mixtures have lower shear strengths than pure sand. Compared with the tests in sand, the hexagonal wire reinforcement in the rubber tire chips with and without sand mixtures had lower pullout resistances. However, with increasing sand content in the mixtures, the pullout resistances of hexagonal wire in mixtures increased. The proposed empirical equations successfully predicted the pullout resistances of hexagonal wire with different mixing ratios. Based on limit equilibrium method, the results of the parametric studies of a reinforced wall for the required spacing and embedment length of hexagonal wire reinforcement have been presented. For a reinforced wall, the total amount of the required hexagonal wire reinforcement in rubber tire chip fill is less than in sand and tire chip-sand fills. Furthermore, the required embedment length of the hexagonal wire reinforcement in sand and tire chip-sand fills is approximately identical, but lower than those in tire chip fill.

Analysis of inextensible sheet reinforcement subject to transverse displacement/force: linear subgrade response

Reinforced earth fills, ground and slopes counteract the destabilizing forces by mobilising tensile forces in the reinforcement. In most studies, the pull-out resistance due to only axial pull is considered in the analysis for stability. However, the kinematics of failure clearly establishes the reinforcement being displaced obliquely. In this paper, a new approach is presented for the analysis of sheet reinforcement subjected to transverse force. Assuming a simple Winkler type response for the ground and the reinforcement to be inextensible, the resistance to transverse force is estimated. The response to the applied force is shown to depend not only on the interface shear characteristics of the reinforcement but also on the deformational response of the ground. A relation is established between pull-out resistance and transverse free end displacement. A parametric study quantifies the contributions of depth of embedment, length and interface characteristics of the reinforcement, stiffness of the ground, etc. on the over all response. It is established that reinforcement in dense granular fills subjected to a transverse pull generates pull-out resistances larger than purely axial pull-out capacity in reinforced earth construction.

Effects of hole preparation on screw pullout resistance and insertional torque: a biomechanical study.

The authors conducted a study to assess the effect of a pilot hole preparation on screw pullout resistance and screw insertional torque. Three different screws were tested: cancellous lateral mass screws, cortical lateral mass screws, and pedicle screws. Synthetic bone blocks were used as the host material. Each screw group was separated into two subgroups. The first subgroup of screws was inserted into the test material following pilot hole preparation. Pilot holes were prepared; a drill bit diameter size smaller than the core diameter of the screws was used. The second group of screws was inserted into the test material without pilot hole preparation (a 3- or 4-mm hole drilled for entrance site preparation only). The insertional torque was measured as the screw was advanced into the material. The screws were axially extracted from the host material at a constant speed of 2.5 mm/minute. The pullout resistances and insertional torques for the pilot hole and the nonpilot hole groups were then statistically compared. The authors found that preparation of a pilot hole caused a significant decrease in the insertional torque. The screws inserted without a pilot hole showed greater pullout resistances compared with those inserted following a pilot hole preparation; however, there was no statistically significant difference. The optimum screw insertion technique may involve drilling a short pilot hole and using a drill bit with a smaller diameter than the screw core diameter to increase bone-screw purchase. This applies to cancellous and cortical lateral mass screws as well as pedicle screws.

Shearing and Friction in the Pullout Behaviour of Woven Geotextiles for Reinforcement Applications

The apparent frictional resistance developed in a pullout operation is generally the result of complex phenomena occurring at the soil–geotextile interface. In this study, an attempt is made to characterize the apparent pullout frictional resistance, which is presumably developed because of soil shearing and soil–geotextile friction at the interface. To illustrate this, the pullout resistances of two different woven geotextile samples with sand are evaluated in the laboratory, and their shearing and friction constituents are calculated. The individual interface areas responsible for shearing and/or friction are found to be important for developing pullout resistance.

Effects of Cross-Sectional Stress-Relaxation on Handling Characteristics of Suture Materials

Pullout friction and cross-sectional relaxation tests were conducted to quantitatively evaluate the handling characteristics of braided suture. The excellent handling of silk suture could be explained in terms of a large difference between static and dynamic pullout resistances. The difference in the resistance was closely correlated to the slope of the cross-sectional relaxation versus time logarithmic plot. It was therefore concluded that the cross-sectional stress-relaxation plays an important role in the handling performance of braided sutures.

Interaction behaviour of steel grid reinforcements in a clayey sand

The interaction behaviour between steel grid reinforcements and a clayey sand has been studied in laboratory and field pullout tests. The clayey sand is potentially useful as cheap, low quality, locally available and cohesive-frictional backfill in the construction of mechanically stabilized earth walls and embankments, especially in coastal areas. The laboratory tests were conducted under undrained conditions at three compaction moisture conditions. The field tests were conducted on dummy reinforcements embedded at different elevations in a full-scale test embankment resting on soft clay foundation. The laboratory tests revealed that the moisture content of the compacted soil, compaction stress, applied normal stress level, diameter and spacing to diameter ratios of the transverse members of the steel grid, all affect the soil-reinforcement interaction, and thereby, also the magnitudes of the pullout resistances. Interferences between the bearing transverse members of the grid were found to be less significant for spacing to diameter ratios above 75. The laboratory tests, in general, gave conservative values of the pullout resistances as compared with the field tests. The proposed prediction equations agreed well with the experimental data. L'interaction entre les renforcements par treillis métalliques et les sables argileux a été étudiée à l'aide d'essais de traction en laboratoire et sur chantier. Le sable argileux est utilisé pour construire des murs en terre mécaniquement stabilisés et des remblais, dans les zones littorales notamment. Ce type de matériau est en effet un matériau de remplissage cohérent-frottant bon marché, de qualité médiocre et disponible localement. Les essais de laboratoire ont été menés, dans des conditions non-drainées, avec trois teneursen eau de compactage. Les essais de chantier ont été réalisés sur des renforcements ancrés à différentes profondeurs dans un remblai grandeur nature reposant sur des argiles molles. Les essais de laboratoire ont montré que la teneur en eau du sol compacté, la contrainte de compaction, le niveau de contrainte normale, le diamètre et les rapports espacement-diamètre des composants transversaux du treillis métallique jouent sur les interactions renforcement-sol, et par conséquent, sur la grandeur de la résistance à la traction. Les interférences entre les éléments porteurs transversaux du treillis semblent moins importantes pour des rapports espacement-diamètre supérieurs à 75. Les essais de laboratoire donnent, en général, des valeurs de résistance en traction plus reproductibles que celles obtenues dans les essais de chantier. Les équations proposées pour la prédiction du comportement sont en bon accord avec les données expérimentales.

Interaction of lateritic soil and steel grid reinforcement

Laboratory and field pullout tests were carried out to study the interaction of welded steel grid reinforcements embedded in lateritic residual soil backfill. The laboratory pullout tests were conducted on various reinforcement sizes, mesh geometries, normal pressures, and compaction conditions of the backfill material. Field pullout tests were conducted at representative overburden, field-moisture, and density conditions. From the test results, it was found that the longitudinal members yielded frictional resistance from 8 to 15% of the total grid pullout resistance. Thus, the major contribution to the pullout resistance of grid reinforcements consists of the passive resistance mobilized in front of the transverse members. The maximum pullout resistance is shown by a bilinear curve which displayed similarity with the failure envelope from direct shear tests of the backfill material. This bilinear envelope reinforced the previous observation regarding the effect of particle breakage phenomenon inherent to lateritic residual soils subjected to high normal pressures. Comparisons between laboratory and field pullout resistances and between the predicted passive resistance and the laboratory test data are also presented. Key words : reinforcement, laboratory test, earthfill, compaction, friction resistance.

Pullout Tests Using Steel Grid Reinforcements with Low‐Quality Backfill

Both laboratory and field pullout tests are conducted using steel grid reinforcements with cohesive-frictional backfill soils. The laboratory pullout tests are performed using a large-scale pullout apparatus designed especially for this study. The field pullout tests are performed on the dummy welded-wire reinforcements embedded in a full-scale reinforced test wall/embankment system that utilize three different locally available, low-quality, cohesive-frictional backfill soilds, namely, clayey sand, lateritic soil, and weathered clay, in the three sections along its length. It is observed that the magnitudes of the mobilized field pullout resistances as well as the strains induced in the reinforcing elements are strongly influenced by the response of the wall/embankment system to the subsoil movements and the resulting arching effects due to the presence of the inextensible reinforcements. Meanwhile, the laboratory pullout test results generally seem to provide a conservative approximation of the field pullout resistances of the grid reinforcements in cohesive-frictional backfills. Using the finite element method to model the laboratory pullout tests, the analytical results are observed to agree fairly well with the experimental results.

Behavior of a welded wire wall with poor quality, cohesive–friction backfills on soft Bangkok clay: a case study

A full-scale and extensively instrumented experimental mechanically stabilized earth (MSE) wall with steel grid reinforcements was built on soft clay foundation. Three different locally available poor to marginal quality backfills were used in each of three sections along its length. The soft Bangkok clay in the subsoil is about 6 m thick, overlain by a surficial 2 m thick weathered clay crust and underlain by a layer of stiff clay. It was observed that the amount of subsoil movement greatly influenced the variation in the vertical pressure beneath the wall, as well as the tension in the reinforcement. Pullout resistances in the field were also found to be very much affected by the arching effects due to the presence of inextensible reinforcement in combination with the subsoil movements. The wall showed no signs of instability both during construction and in the postconstruction phases, despite the large settlements and lateral movements. Its overall performance has been satisfactory. It was concluded that the steel grid reinforcement can be effectively used to reinforce poor to marginal quality backfill in walls and embankments on soft clay foundations. Key words: mechanically stabilized earth, inextensible reinforcements, soft clay foundation, poor quality backfills, base pressures, settlements, lateral movements, lateral pressures, compaction, arching.

Marine Curing of Steel Fiber Composites

With the attractive possibility of offshore concrete casting in mind, the effects of marine curing on the pull-out behavior of steel fibers were investigated. Single fiber pull-out specimens were chosen to clearly examine the behavior of individual fibers. Three curing temperatures of 2°, 22°, and 38°C were chosen. Deformed fibers with hooks on both ends were chosen. The effects of silica fume addition were also investigated. Pull-out resistances were continuously monitored by conducting tests starting at the age of 1 day up to about 3 months. In some cases, the tests were extended to an age of 1 year. Some fibers were retrieved and examined in a scanning electron microscope. Curing at a low temperature of 2°C was not found to adversely affect the pull-out resistance even after one year of continuous marine exposure. High temperatures, however, were found to promote an early corrosion leading to substantial reductions in pull-out resistances. The presence of silica fume was not found to promote strength retrogression in any particular way. The deformed locations of the fibers, perhaps because of the residual stresses, were found to be particularly susceptible to anodic pitting.

Some Studies on Anchor Plates in Sand

A number of laboratory tests on pullout resistances of square and rectangular model anchors made of aluminium plates in loose sand have been taken up for this investigation. The main purpose of this paper is to present some recent model test results for square and rectangular plates in sand at constant compactive effort and outlines the pullout resistance of anchor plates with a vertical axis of different sizes and a load displacement relationship of the model tests. Moreover, the ultimate anchor resistance has been expressed in terms of nondimensional force coefficient and breakout factor. For rectangular and square anchors, the breakout factor increases with relative depth of embedment ratio to a certain extent and then tends to approximately constant at greater depths. The critical embedment ratio for rectangular anchors is about five while there is no meaningful results in case of square anchors. An attempt has also been focussed to understand the basic behavior of embedded anchors. The depth of embedment, size of anchors and the relative density of the sand are also important factors in this investigation.

Pullout Resistance of Vertical Anchors

In an investigation of the pullout resistances of shallow vertical square and circular anchors, eight model anchors (4 were square and 4 were circular) made of 0.125-in. thick aluminum plates were laboratory tested in a sand box measuring 2 ft x 2 ft x 2 ft. Details are given of the tests (each was repeated three times) in which sand was recompacted for the entire depth of embedment for each test run. The results of each set of tests varied less than 4 percent. An average load-displacement diagram is presented and the average ultimate load for all sets is tabulated. The analysis of the results is detailed. It is concluded on the basis of the study that with h = d (h = size of square plates and d = size of circular plates), the ultimate passive resistance of a circular anchor is approximately 66 percent of that for a square anchor.