Geosynthetics International: Vol.8, No. 5, 2001

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FIELD PERFORMANCE OF A 17 M-HIGH REINFORCED SOIL RETAINING WALL

ABSTRACT: A 17 m-high steel strip reinforced soil retaining wall was instrumented to compare field measurements with predictions given by the design guidelines of the American Association of State Highway and Transportation Officials (AASHTO) 1996 Standard Specifications and the AASHTO 1999 Interim Revisions. The AASHTO models were conservative with respect to external lateral earth pressures and lateral earth pressures on the facing panels. On average, the AASHTO 1996 and 1999 models overestimated lateral pressure at the facing by 94 and 142%, respectively. Measured values of foundation bearing stress were generally in good agreement with values calculated using soil unit weight and depth, except that the average force from the facing panels on the leveling pad was twice that of the weight of the panels themselves. This discrepancy is attributed to shear stress on the back of the facing panels and vertical loads transferred to the panels through the strip connection clips. The location of the zone of maximum strip tension was in good agreement with the assumed failure surface. On average, the AASHTO 1996 and 1999 models underestimated maximum strip tensions by 17 and 8% and overestimated strip connection tensions by 127 and 154%, respectively. Finally, the apparent soil-reinforcement friction coefficient for the ribbed steel strips exceeded values specified in the AASHTO models by an average of 132%.

KEYWORDS: Retaining wall, Reinforced soil, Earth pressure, Instrumentation.

AUTHORS:
D.J. Runser, Geotechnical Engineer, Van Deurzen and Associates, P.A., Overland Park, Kansas 66210, USA, Telephone: 1/913-451-6305, Telefax: 1/913-451- 1021, E-mail: drunser@vandeurzenassoc.com, formerly, Graduate Research Assistant, School of Civil Engineering, Purdue University;
P.J. Fox, Associate Professor, Dept. of Civil and Environmental Engineering, University of California, Los Angeles, California 90095, USA, Telephone: 1/310-794-4805, Telefax: 1/310-206-2222, E-mail: pfox@seas.ucla.edu; and
P.L. Bourdeau, Associate Professor, School of Civil Engineering, Purdue University, West Lafayette, Indiana 47907, USA, Telephone: 1/765- 494-5031, Telefax: 1/765-496-1364, E-mail: bourdeau@ecn.purdue.edu.

DATE: Original manuscript submitted 19 September 2000, revised version received and accepted 24 September 2001. Discussion open until 1 June 2002.

REFERENCE: Runser, D.J., Fox, P.J., and Bourdeau, P.L., 2001, “Field Performance of a 17 m-High Reinforced Soil Retaining Wall”, Geosynthetics International, Vol. 8, No. 5, pp. 367-391.

Technical Paper by H.S. Roh and F. Tatsuoka

EFFECTS OF PRELOADING AND PRESTRESSING ON THE STRENGTH AND STIFFNESS OF EOSYNTHETIC REINFORCED CLAY IN PLANE STRAIN COMPRESSION

ABSTRACT: A series of plane strain compression (PSC) tests was performed to evaluate effects of preloading and prestressing on the stress-strain properties of reinforced saturated relatively soft clay. Saturated specimens of compacted clay, either unreinforced or reinforced with two horizontal layers of a composite consisting of woven and nonwoven geotextiles, were consolidated anisotropically simulating typical field stress conditions. Without drained preloading, the undrained strength of reinforced clay specimens did not noticeably increase when compared to unreinforced specimens, because a high positive excess water pressure developed in the reinforced clay due to the original high contractibility of the clay, which was not eliminated by reinforcement alone. The drained compressive strength increased substantially with reinforcement, while the peak strength was attained only at a large strain and the initial stiffness did not increase. By drained preloading to a load level that was much higher than the drained strength of unreinforced clay, the overall pre-peak stiffness, yield strength, and peak strength of reinforced clay under undrained conditions became substantially larger than those of unreinforced clay that had not been preloaded. The initial stiffness of preloaded clay at small strains became larger with increases in the prestress level as long as the prestress level was not too close to the preload level.

KEYWORDS: Preloading, Prestressing, Geosynthetic-reinforced saturated clay, Plane strain compression test, Initial stiffness, Shear strength, Undrained shearing.

AUTHORS:
H.S. Roh, Professional Engineer, Soil and Foundation Engineering Division, Highway Research Center, Korea Highway Research Center, 293-1 Keumtodong, Sujeong-gu, Seongnam-si, Kyonggi-do, Republic of Korea, Telephone: 82/2- 2230-4656, E-mail: hsroh@freeway.co.kr.; and
F. Tatsuoka, Professor, Department of Civil Engineering, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113, Japan, Telephone: 81/3-5841-6120, E-mail: tatsuoka@geot.t.u-tokyo.ac.jp.

DATE: Original manuscript submitted 27 June 2001, revised version received 11 September 2001, and accepted 14 September 2001. Discussion open until 1 June 2002.

REFERENCE: Roh, H.S. and Tatsuoka, F., 2001, “Effects of Preloading and Prestressing on the Strength and Stiffness of Geosynthetic-Reinforced Clay in Plane Strain Compression”, Geosynthetics International, Vol. 8, No. 5, pp. 393-444.

Technical Paper by A. Fakher and C.J.F.P. Jones

WHEN THE BENDING STIFFNESS OF GEOSYNTHETIC REINFORCEMENT IS IMPORTANT

ABSTRACT: A numerical simulation has been undertaken to model a layer of sand overlaying a layer of geosynthetic reinforcement and super soft clay. Details of the model and the modelling procedures are described and the influence of the bending stiffness (flexural rigidity) of the reinforcement on the bearing capacity of super soft clay is discussed. Factors affecting the reinforcement mechanisms of geosynthetic reinforcement of super soft clay are considered.

KEYWORDS: In-plane bending stiffness, Geosynthetic reinforcement, Super soft clay, Primary stage construction, Reinforced soil.

AUTHORS:
A. Fakher, Lecturer, Department of Civil Engineering, Tehran University, Iran, Telephone: 98/21-649-8981, Telefax: 98/21-646-1024, E-mail: afakher@ut.ac.ir; and
C.J.F.P. Jones, University of Newcastle upon Tyne, Department of Civil Engineering, Drummond Building, Newcastle upon Tyne, NE1 7RU, United Kingdom, Telephone: 44/191-222-7117, Telefax: 44/191-222-6613, E-mail: c.j.f.p.jones@ncl.ac.uk.

DATE: Original manuscript submitted 1 September 2001, revised version received 1 November 2001, and accepted 5 November 2001. Discussion open until 1 June 2002.

REFERENCE: Fakher, A. and Jones, C.J.F.P., 2001, “When the Bending Stiffness of Geosynthetic Reinforcement is Important”, Geosynthetics International, Vol. 8, No. 5, pp. 445-460.

Technical Note by G.L. Sivakumar Babu, H. Sporer, H. Zanzinger, and E. Gartung

SELF-HEALING PROPERTIES OF GEOSYNTHETIC CLAY LINERS

ABSTRACT: The sealing effect and containment of moisture in landfill covers and liners containing geosynthetic clay liners (GCLs) are largely influenced by moisture retention, swelling, and the self-healing behaviour of bentonite used in GCLs. The method of binding of GCLs also significantly affects the behaviour. To examine these aspects, percent swell and swell pressure tests under different effective pressures were conducted on two sodium-based GCLs. Permittivity tests were performed on GCL specimens with different hole diameters and also on specimens dried at 20 and 60oC. The test results are presented and discussed. The study shows that the GCLs considered have a good self-healing capacity for the case of desiccation cracks or punctures. In addition, the method of binding the GCL components, i.e., stitch-bonded or needlepunched, has a significant influence.

KEYWORDS: Geosynthetic clay liner, Self healing, Swell, Bentonite, Permittivity test.

AUTHORS:
G.L. Sivakumar Babu, Assistant Professor, Department of Civil Engineering, Indian Institute of Science, Bangalore, India, 560012, Telephone: 91/80-3092672, Telefax: 91/80-3600404, E-mail: gls@civil.iisc.ernet.in; and
H. Sporer, Telephone: 49/ 911-655-5687, Telefax: 49/911-655-5592, E-mail: gbsp@lga.de,
H. Zanzinger, Telephone: 49/911-655-5563; Telefax: 49/911-655-5592, E-mail: helmut.zanzinger@lga.de, and
E. Gartung, Telephone: 49/911-655-5561; Telefax: 49/911-655-5599, E-mail: gbgg@lga.de, LGA (Grundbauinstitut), Tillystr. 2, D-90431 Nuremberg, Germany.

DATE: Original manuscript submitted 25 September 2000, revised version received 26 August 2001, and accepted 6 September 2001. Discussion open until 1 June 2002.

REFERENCE: Sivakumar Babu, G.L., Sporer, H., Zanzinger, H., and Gartung, E., 2001, “Self-Healing Properties of Geosynthetic Clay Liners”, Geosynthetics International, Vol. 8, No. 5, pp. 461-470.