Pullout Resistance Factors for Inextensible Mechanically Stabilized Earth Reinforcements in Sandy Backfill

2013 ◽  
Vol 2363 (1) ◽  
pp. 21-29 ◽  
Author(s):  
William D. Lawson ◽  
Priyantha W. Jayawickrama ◽  
Timothy A. Wood ◽  
James G. Surles
Keyword(s):  
Large Scale ◽  
Steel Strip ◽  
Mechanically Stabilized Earth ◽  
Overburden Pressure ◽  
Welded Steel ◽  
Pullout Resistance ◽  
Resistance Factors ◽  
Granular Fill ◽  
Mechanically Stabilized ◽  
Grid Reinforcement

This paper presents results from a laboratory program of 402 pullout tests of inextensible reinforcements used for walls of mechanically stabilized earth (MSE). Results focus on the evaluation of pullout resistance factors for ribbed-steel strip and welded-steel grid reinforcements embedded in sandy backfill that marginally met AASHTO requirements for select granular fill. This project used Texas Tech University's large-scale MSE test box with dimensions of 12 3 12 3 4 ft and an applied overburden capacity of 40 ft of backfill. This test box facilitated pullout testing at a scale not unlike typical field construction. The research design evaluated pullout resistance factors for both ribbed-strip and welded-grid reinforcements for a variety of independent variables, including overburden pressure, reinforcement length, level of compaction, grid wire size, and grid geometry, such as transverse and longitudinal wire spacing. Appropriate statistical analyses were used to interpret the data within the context of published AASHTO design guidance for inextensible MSE reinforcements. The results show that pullout behaviors of both ribbed strips and welded grids in properly compacted sandy backfill are conservative compared with the default pullout resistance factors provided by AASHTO. The data also suggest that the current AASHTO equations for pullout resistance factors for grid reinforcement do not accurately capture the influence of transverse and longitudinal bar spacings.

Experimental analysis of large-scale pullout tests conducted on polyester anchored geogrid reinforcement systems

2017 ◽  
Vol 54 (5) ◽  
pp. 621-630 ◽  
Author(s):  
S.H. Sadat Taghavi ◽  
M. Mosallanezhad
Keyword(s):  
Large Scale ◽  
Mechanically Stabilized Earth ◽  
Height Ratio ◽  
Passive Resistance ◽  
Pullout Resistance ◽  
Pullout Tests ◽  
Mse Walls ◽  
Effective Performance ◽  
Mechanically Stabilized ◽  
New System

The pullout resistance of reinforcement, such as geogrids in mechanically stabilized earth (MSE) walls, includes the skin friction between the soil and solid geogrid surfaces. It also includes the bearing resistance against the transverse ribs, which has a greater influence on the production of pullout resistance. Taking the current limitations involved in producing woven polyester geogrids into consideration (i.e., the limited thickness of the transverse ribs), the amount of bearing resistance developed in front of transverse ribs is limited in the pullout mechanism. Thus, along with introducing an innovative and applied system, this research has endeavoured to demonstrate the effective performance of this new system in increasing the passive resistance — and thereby the pullout resistance — of standard geogrids. This new system, which is formed by adding steel transverse elements (a set of steel equal angles) to the ordinary polyester geogrids by means of nuts and bolts, is called an anchored geogrid (AG). The experimental results show that a spacing-to-height ratio of transversal elements equal to 5 gives the maximum pullout resistance for a polyester AG system in sandy soil used in the study. With an optimum arrangement, this system is capable of increasing the pullout resistance of the ordinary geogrid system by 65%. In addition, based on the plasticity solution, the pullout bearing failure mechanisms of a single isolated transverse element in the polyester AG system depend on overburden pressures.

Pullout Behavior of Steel Mechanically Stabilized Earth Reinforcements

2018 ◽  
Vol 2672 (52) ◽  
pp. 238-250 ◽  
Author(s):  
Timothy A. Wood ◽  
William D. Lawson ◽  
Priyantha W. Jayawickrama ◽  
James G. Surles
Keyword(s):  
Axial Force ◽  
Stress Reduction ◽  
Soil Reinforcement ◽  
Mechanically Stabilized Earth ◽  
Pullout Resistance ◽  
Pullout Tests ◽  
Earth Reinforcement ◽  
Embedment Length ◽  
Mechanically Stabilized ◽  
Reinforcement Interaction

Instrumented pullout tests of unprecedented scope and scale explore the pullout behavior for three steel mechanically stabilized earth reinforcement types: ribbed strips, ladder-like strips, and three-wire bar mat grids. These data quantify the distribution of pullout resistance between longitudinal elements and illustrate the nature of certain reinforcement deformations. Consistent with characteristic inextensible pullout behavior and soil-reinforcement interaction, synthesized strain-gage data illustrate linear stress reduction along the embedment length during pullout for all three reinforcement styles. For ladder-like strips, the axial force divides evenly between the two longitudinal elements. For the three-wire bar mat grid, the center bar carries approximately 40% of the axial force, whereas each outside bar carries approximately 30% of the axial force. Observed pullout-induced deformation in the transverse elements of three-wire bar mat grids having widely spaced longitudinal bars is conceptually different from extensible behavior and suggests the need for refinement in current pullout resistance formulations.

scholarly journals Experimental Study on the Pullout Resistance of Smooth Steel Strip Reinforcement with Transverse Members

2021 ◽  
Vol 11 (6) ◽  
pp. 2776
Author(s):  
Jung-Geun Han ◽  
Kwang-Wu Lee ◽  
Jong-Young Lee ◽  
Gigwon Hong ◽  
Jeongjun Park
Keyword(s):  
Experimental Study ◽  
Normal Stress ◽  
Interference Effect ◽  
Large Scale ◽  
Steel Strip ◽  
Prediction Method ◽  
Pullout Resistance ◽  
Reasonable Prediction ◽  
Distributed Friction ◽  
The Relationship

This paper presents an experimental study on the pullout resistance of a newly improved reinforcement. The applied reinforcement was a smooth steel strip reinforcement with transverse members used to improve the pullout-resistance problems of the smooth steel strip reinforcement. The pullout and bearing resistance of the improved reinforcement were evaluated using results of large-scale pullout tests. The evaluation result confirmed that the bearing resistance of the improved reinforcement was about 33–66% of the total pullout resistance, and it had an evenly distributed friction and bearing resistance. The bearing bond coefficient, considering the interference effect, gradually converged when normal stress was higher than a certain value. This result confirmed that the increment of interference effect is caused by the increment of the transverse member and normal stress. In the pullout-resistance evaluation of the improved reinforcement, a number of transverse members can be predicted using the relationship between bearing-resistance stress and the bearing bond coefficient due to normal stress, which can be applied as a reasonable prediction method.

Laboratory Experimental Study on Pullout Behavior of Mortar Grouted GFRP Soil Nails

2010 ◽  
Vol 168-170 ◽  
pp. 1069-1072
Author(s):  
Zhong Yu Liu ◽  
Chong Wu Ma ◽  
Zhuo Zhao
Keyword(s):  
Large Scale ◽  
Axial Strain ◽  
Hyperbolic Function ◽  
Overburden Pressure ◽  
Soil Nails ◽  
Pullout Resistance ◽  
Pull Out ◽  
Glass Fiber Reinforced ◽  
Dilatancy Effect ◽  
Pullout Load

A large-scale laboratory apparatus has been built to study the pullout behavior of mortar grouted glass fiber reinforced polymer (GFRP) soil nails. The axial strain along the nail length and the displacement of the nail head under different pullout loads are measured, and the ultimate pullout load under the overburden pressure is obtained. Then, the influence of the overburden pressure on the ultimate value of the interface friction force is investigated. The experimental results illustrate that the pullout behavior of mortar grouted GFRP soil nails is similar to that of mortar grouted steel soil nails, and the relation between the displacement and the pullout load can be described with the hyperbolic function. In addition, the dilatancy effect of the soil near the nail during pull out should be taken into account in estimating the pullout resistance of soil nails in dense fills.

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

1991 ◽  
Vol 28 (6) ◽  
pp. 860-880 ◽  
Author(s):  
D. T. Bergado ◽  
R. Shivashankar ◽  
C. L. Sampaco ◽  
M. C. Alfaro ◽  
L. R. Anderson
Keyword(s):  
Key Words ◽  
Soft Clay ◽  
Poor Quality ◽  
Mechanically Stabilized Earth ◽  
Mse Wall ◽  
Overall Performance ◽  
Stiff Clay ◽  
Mechanically Stabilized ◽  
Grid Reinforcement

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.

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