Hoe I. Ling

Post-earthquake investigation on several geosynthetic-reinforced soil retaining walls and slopes during the Ji-Ji earthquake of Taiwan

Abstract This paper gives an overview on the application of geosynthetic-reinforced soil structures in Taiwan. Taiwan has an unique topography and geotechnical conditions that rendered a less conservative and more challenging design compared to that of North America, Europe and Japan. The Ji-Ji (Chi-Chi) earthquake of 1999 gave an opportunity to examine the behavior of reinforced soil structures. The performance of several modular-block reinforced soil retaining walls and reinforced slopes at the vicinity of the fault was evaluated. Reinforced structures performed better than unreinforced soil retaining walls. The failure cases were highlighted and the cause of failure was identified. The lack of seismic design consideration could be a major cause of failure. The compound failure mode, the inertia force of the blocks, and the connection stiffness and strength relative to the large dynamic earth pressure, were among major items that would warrant further design consideration.

Soil slopes under combined horizontal and vertical seismic accelerations

Conventional methods of designing earth structures are based on pseudo-static stability analysis employing a horizontal seismic coefficient. This paper discusses the stability and permanent displacement of a slope subject to combined horizontal and vertical accelerations. A log-spiral failure mechanism is used. It is shown that seismic force has a significant effect on stability and permanent displacement of slopes. The parametric study reveals that vertical acceleration may play an important role on stability and permanent displacement if the corresponding horizontal acceleration is large.

Effects of Geocell Confinement on Strength and Deformation Behavior of Gravel

AbstractIn past years, railroad transportation has been of growing interest because of its efficiency and advancement in railway technologies. However, many issues arise because of the variability in subsurface conditions along the sizeable lengths of track that exist. One very important issue is the need for significant upkeep and maintenance for railways passing over areas of poor soil conditions as a result of continuous deformation and a lack of stiffness from the foundation. One general solution for lack of substructure integrity has been confinement, applied through a variety of reinforcement types, including geocell. To investigate the effectiveness of geocell confinement on substructure integrity, a series of embankment model tests with different configurations of geocell placement (one layer and two layers of geocell) were constructed and loaded monotonically and cyclically for comparison with unreinforced, control tests. On the completion of these tests, the model embankments were simulated nume...

Recent applications of sliding block theory to geotechnical design

The sliding block theory was proposed by Newmark for determining the permanent displacement of embankments and dams under earthquake loading. This paper highlights recent applications of sliding block theory to different geotechnical structures. The equations to determine seismic factor of safety, yield acceleration and permanent displacement are given for rock block, soil slope, landfill cover, geosynthetic-reinforced soil retaining wall, and composite breakwater. The presented equations for seismic stability degenerate to that of static stability in the absence of earthquake. The permanent displacement for various structures can be obtained from that of a horizontal sliding block through a correction factor. A simplified procedure is included for the permanent displacement under vertical acceleration. The sliding block approach is rational for design under high seismic load.

Rock sliding induced by seismic force

Failure analyses of rock masses are frequently encountered in major civil engineering construction and mining, and in particular for projects related to slope excavation. The proposed procedure determines the seismic factor of safety against sliding along a joint plane.

Finite-Element Simulations of Full-Scale Modular-Block Reinforced Soil Retaining Walls under Earthquake Loading

A finite-element procedure was used to simulate the dynamic behavior of four full-scale reinforced soil retaining walls subjected to earthquake loading. The experiments were conducted at a maximum horizontal acceleration of over 0.8 g, with two walls subjected to only horizontal accelerations and two other walls under simultaneous horizontal and vertical accelerations. The analyzes were conducted using advanced soil and geosynthetic models that were capable of simulating behavior under both monotonic and cyclic loadings. The soil behavior was modeled using a unified general plasticity model, which was developed based on the critical state concept and that considered the stress level effects over a wide range of densities using a single set of parameters. The geosynthetic model was based on the bounding surface concept and it considered the S-shape load-strain behavior of polymeric geogrids. In this paper, the calibrations of the models and details of finite-element analysis are presented. The time response of horizontal and vertical accelerations obtained from the analyses, as well as wall deformations and tensile force in geogrids, were compared with the experimental results. The comparisons showed that the finite-element results rendered satisfactory agreement with the shake table test results.

SHORT-TERM STRENGTH AND DEFORMATION CHARACTERISTICS OF GEOTEXTILES UNDER TYPICAL OPERATIONAL CONDITIONS

Abstract An apparatus capable of measuring the strength and deformation properties of geotextiles under unconfined conditions and under the confinement of a membrane or a soil was developed. The appratus differed from conventional in-soil test apparatuses in that during the soil-confinement test the soil was allowed to deform with the geotextile while being confined by a prescribed pressure — simulating the predominant operational condition of geotextiles in reinforced soil structures. Three non-woven geotextiles manufactured in different materials and by different bonding processes were used in this study, and their stress-confinement effects were studied. It was shown that the stress-confinement effect existed in the spun-bonded and needle-punched geotextiles but not in the heat-bonded geotextile. The effect of using different materials (membrane and soil) for the confinement was also studied. Under otherwise identical conditions, the results were very similar between the in-membrane and in-soil tests. It was concluded that the in-membrane test is sufficient for evaluating the load-deformation properties of geotextile. Mathematical models were used to represent the measured load-deformation relationships of the geotextiles, and their accuracy was discussed.

Centrifuge Modeling of Slope Instability

This paper demonstrates the use of a centrifuge modeling technique in studying slope instability. The slope models were prepared from sand, and sand mixed with 15 and 30% fines by weight, compacted at optimum water content. The validity of the modeling technique was confirmed using slope models of different heights, inclinations, and soil types. The soil behavior was studied under triaxial and plane strain conditions, and the extended Mohr-Coulomb failure criterion was found relevant for expressing the strength of unsaturated compacted soil based on the angle of internal friction and apparent cohesion. The Bishops circular mechanism, together with the extended Mohr-Coulomb failure criterion, was able to simulate the slope failure reasonably well. The rainfall of different intensities was then induced on the 60° stable slopes of sand with 15% fines. It was found that the failure of slope under rainfall may be interpreted as a reduction in apparent cohesion. The centrifuge tests also allowed the rainfall intensity-duration threshold curve (local curve) to be generated for the test slopes, and the accumulated rainfall corresponded well to some of the reported field observations.

Reinforced soil engineering : advances in research and practice

Civil and environmental applications of geosynthetics, Hoe I. Ling performance properties of geogrids, Wim Voskamp unit cell testing of reinforced soils, Hoe I. Ling Modelling the time-dependent behaviour of geosynthetically reinforced soilstructures with cohesive backfill, Victor N. Kaliakin and M. Dechasakulsom issue and nonissue in block walls as implied through computer-aided design, Dov Leshchinsky application of sliding block concept to geosynthetic-constructed facilities, Hoe I.Ling failure of an 8-m-high segmental block wall in the northeast United States, C.M. Reith, G.S. Paxson, and A.W. Cadden displacement monitoring at Verrand high reinforced-soil structure, G. Sembenelli and P. Sembenelli UD case study - BluewaterRetail and Leisure Destination reinforced soil slopes to form steep-sided new lakes, J.H. Dixon state of the practice - past, current and future perspectives of reinforced soil retaining structures in Turkey, Muhannad Ismeik and Erol Guler recentexperiences of reinforced retaining structures in China, Li Guangxin and Wang Zhao large-scale reinforced clay walls backfilled with clay at Cheng Kung University, Ching-Chuan Huang, H.Y. Shan, G.Y. Jean, and A.L. Leu geotextile reinforced abutments onsoft foundation, Ennio M. Palmeira, Andre Fahel, and Luiz E.P. Campos geosynthetic reinforcement in the mitigation of pipeline flotation, Yoshiyuki Mohri, Toshinori Kawabata and Hoe I. Ling practice and research of geosynthetic reinforced soil walls inAustralia, Sik-Cheung Robert Lo geosynthetic reinforced containment dyke constructed over soft foundation - numerical analysis, Hoe I. Ling, Dongyi Yue and Victor N. Kaliakin post-earthquake investigation of several geosynthetic reinforced soilretaining walls and slopes during Ji-Ji earthquake of Taiwan, Hoe I. Ling and Dov Leshchinsky tests on seismic stability of several types of soil retaining walls, Junichi Koseki, Kenji Watanabe, Fumio Tatsuoka, Masaru Tateyama, Kenichi Kojima and YulmanMunaf performance of geosynthetics reinforced soil wall and reinforced earth wall subject to blast loading - experimental and numerical study, Tan Siew Ann shaking table tests of embankment models reinforced with geotextiles, S. Tani, S. Ihara, Y.Yokota, and Y. Okabe centrifuge modelling of seismic performance of reinforced earth structure, Jiro Takemura and Akihiro Takahashi performance analysis of arifiye overpass reinforced earth walls during the 1999 Kocaeli (Turkey) earthquake, C. GuneyOlgun and James R. Martin II dynamic simulation of the reinforced slope failure at the Chi-Nan University during the 1999 Chi-Chi earthquake, Nelson N.S. Chou and Chia-Cheng Fan a compact probabilistic representation -the Chi-Chi earthquake groundmotion, A.W. Smyth, S.F. Masri, and C.H. Loh a critical review of full-scale shaking table tests conducted on reinforced soil retaining walls, Hoe I. Ling.

Effects of sustained and repeated tensile loads on geogrid embedded in sand

Design methods for reinforced soil structures under static loading conditions are relatively well established. Little research has been conducted on the behavior of embedded geosynthetics subjected to repeated loadings. Such research is needed to improve the design of reinforced soil structures subjected to traffic and seismic loadings. The study reported here is related to the long-term performance of a geogrid embedded in Ottawa sand under several confining pressures and subjected to various tensile loads. Different magnitudes of sustained and repeated tensile loads were applied to the geogrid incrementally using a pullout device. The confining pressure increased the soil-geogrid interface friction force and thus affected strain distribution along the geogrid length. Creep developed in the geogrid as the applied tensile load increased. The geogrid creep strain rate at a given tension force was found to be independent of confining pressure at the point of this force application, that is, creep can be viewed as an intrinsic property of the geogrid. A rapid pullout failure of geogrid occurred as the applied sustained load approached the ultimate pullout capacity. Conversely, under repeated loading the pullout occurred progressively. The ultimate pullout load and interaction coefficient, Ci, obtained from repeated loading tests were about 20% less than the values obtained from sustained loading tests. This suggests that a Ci smaller than that obtained in static (conventional) tests should be used in structures subjected to dynamic load. Creep under repeated load was smaller than that under sustained load.