Reinforced soil geotextiles

Because of the recent rash of hurricanes like Katrina and tsunamis, we have become more aware of the need for protection against their violence. Geotextiles play a major role in this protection. Reinforced soil was used by Babylonians 3000 years ago in the construction of their pyramid-like tower, ziggurats. One of these famous towers, the Tower of Babel, collapsed. For thousands of years, the Chinese used wood, straw, and bamboo for soil reinforcement including the construction of the Great Wall. In fact, the Chinese symbol for civil engineering can be translated as earth and wood. The Dutch have made extensive use of natural fibrous materials in their age-old battle with the sea. The Romans employed wood and reed for foundation reinforcement. By the 1920s, cotton fabrics were tested as a... 

Areas where geotextiles are used as reinforcement include embankment construction, reinforced soil wall construction, and slope improvement. In reinforcement, the physical properties of importance are primarily related to strength, that is, a combination of the stress—strain characteristics of the material. 

Reinforcement. Soil is relatively strong in compression, but very weak in tension. Therefore, if a tensile inclusion (geotextile) is added to the soil and forms an intimate contact with it, a composite material can be formed which has superior mechanical characteristics in... 

For the geotextile to provide an effective reinforcement function, it should have not only a high tensile strength, but also a high tensile modulus so that its resistance to tensile loads generated within the soil occurs at sufficiently small strains to prevent excessive movement of the reinforced soil structure. It is self-evident that decreases in these properties with time (i.e. creep behaviour) must be low, and that the polymers used should have resistance to degradation by the soil. An estimate of the anticipated reduction in strength can be determined from an analysis of creep strain versus time plots for various stress levels and a suitable reduction factor applied. 

The three primary applications of soil reinforcement using geotextiles are ... 

The seismic behaviour of reinforced soil structures has been studied by shaking table tests , where a near full-size geotextile reinforced wall is fitted... 

John, N. (1987), Paulson geosynthetic material and physical properties relevant to soil reinforcement applications. Geotextiles and Geomembranes, 6,211-212. 

Collios, A., Delmas, P, Gourc, J. P. and Giroud, J. P. (1980), Experiments on soil reinforcement with geotextiles. Proceedings of Syrup Use of Geotextiles for Soil Improvement, ASCE, Portland pp. 53-73. 

Athanasopoulos, G. A. (1996), Results of direct shear tests on geotextUe reinforced cohesive soil. Geotextiles and Geomembranes, 14,619-644. 

Alawaji, H. A. (2001), Settlement and bearing capadty of geogrid-reinforced sand over collapsible soil. Geotextiles and Geomembranes, 19, pp. 75-88. 

Krieger, J. and Thamm, B. R. (1991), Studies of failure mechanisms and design methods for geotextile-reinforced soil walls. Geotextiles and Geomembranes, 10,53-63. 

Ovesen, N.K. Krarup, J. 1983. Centrifuge tests of embankments reinforced with geotextiles on soft clay. In Proc 8th European Conf Soil Mech Found Eng. 393-398. 

Stabilization. Geotextiles serve to reinforce the soil, thereby creating the internal stability required (fabric-reinforced soil). Moreover, geotextiles can be placed between two different soil layers with a separation function, preventing the intermixing of the two soil layers due to dynamic loading. 

Palit, S., Datta, U., Chatteijee, P.K., Ghosh, S.N., 1988. Geotextiles a special reference to jute. In First Indian Geotextile Conference on Reinforced Soil and Geotextiles, Bombay, India, pp. G15-G21. 

The active area of mechanically stabilized earth walls and slopes uses geotextile separators in two critical locations covering a base drain beneath the reinforced soil zone and around individual lifts of backfill soil. See Fig. 11.10 for these locations. 

The key properties of geotextiles used in reinforced soil applications are introduced with short explanations. For details about the tests mentioned here, see chapters Hydraulic properties, behavior and testing of geotextiles Long-term geotextile degradation mechanisms and exposed lifetime predictions and Geotextiles used in separation. 

Soil—geotextile interaction in pull-out mode The geotextile length for slope and wall reinforcement is designed to provide anchorage beyond the potential failure surface. Such resistance can be modeled in the laboratory using a puU-out test. The pull-out resistance of the geotextile obtained in the test can be expressed as (Eq. [15.6]) ... 

Design criteria that should be met for a reinforced soil structure with geotextiles can be summarized as follows ... 

---