DESIGN AND APPLICATION OF AASHTO M 288-96 GEOTEXTILE SPECIFICATIONS
本文以AASHTO M 288-96規範為例，闡述地工織物之應用；於特定之應用，地工織物所扮演之功能，及涵蓋紡織及大地工程所應考量之物理、化學及力學因素，需求之地工織物性質，供大地工程師在地工織物應用之省思及參考。
Geotextiles are soft engineering materials. From the end of 1970, geotextile's application in geotechnical engineering has grown rapidly and become a great tool for solving geotechnical problems. Geotextile includes polymer, textile and geotechnical engineerings, although used by geotechnical engineer, its properties and behaviors are related to polymer materials and textile manufacturing process. It is an important topic on how to use geotextile properly.
In this paper, using AASHTO M 288-96 Specifications explains the applications of geotextile. In the specialized applications, the functions of the geotextile and the factors of the physical, chemical and mechanical properties of geotextiles covered in textile and geotechnical engineering as well as required properties for the application are introduced.
Geosynthetics exclusively are human made new construction materials which have influenced the construction in the areas of geotechnical engineering, transportation engineering, environmental engineering, and hydraulics engineering, etc. The families of Geosynthetics include Geotextiles, Geogrids, Geomembranes, Geonets, Geosynthetic clay liners, Geopipes, Geocomposites, and Geofoams. Geosynthetic materials perform seven major functions：separation, reinforcement, filtration, drainage, liquid barrier, protection, and erosion control. For a particular application design, the ultimate decision usually take one of the three directions：design by cost and availability, design by function ,and design by specification. Since the new materials are widely used in various construction, design by specification is very common and exclusively important when dealing with public agencies. The objective of the paper is to review the current common used CNS, ASTM, and GRI test standards for Geotextiles, Geomembranes,and Geogrids.
Geotextiles are used extensively to replace granular soil filters in many geotechnical applications. This paper reviews current criteria used in geotextile filter design. Principle concepts, influence factors, methods of characteristic measurement, as well as recently-developed design procedures are included in this review.
COMPARISON OF FIVE DIFFERENT GEOSYNTHETICS DESIGN CODES
各種地工合成材設計規範之基本觀念互有異同。有的規範會在某些考量較為保守，而在其餘部分較為開放。本文比較了英國BS8006，BE3/78；法國NF P 94－220，德國DIBt，以及美國聯邦公路協會（FHWA）五種設計規範之基本異同觀點。尤其注重在擋土牆設計方面之比較。
Basic design concept of various codes for geosynthetics may be the same on certain points, however, they may also be different on certain other points. The purpose of this paper is to compare the basic design concept of five different design codes, which include UK BS 8006, BE 3/78; France NF P 94-220; Germany DIBt; and USA FHWA codes. The comparison emphasizes on retaining wall design.
To evaluate the performance of geotextiles as separators in roadways, a series of laboratory model tests were conducted to simulate field conditions experienced by geotextiles. In this study, different thicknesses of base courses and geotextiles of various types with various weights were used. The soft subgrades also have different strengths and soil types. These parameters can represent some of the conditions, where geotextiles are used.
In laboratory tests, cyclic loading was applied on aggregates, which were underlain by a geotextile. Underneath the geotextile, a soft soil (clayey soils and silty soils) was prepared by consolidation to simulate a soft subgrade in a field. During cyclic loading, the depression at aggregate surface and porewater pressure within soft subgrade were monitored. In this paper, the performance of geotextiles are evaluated in terms of separation, survivability, drainage, filtration and reinforcing. Based on the results, the separation function of geotextiles are found promising, if they survived under the dynamic loadings. In contrast with control tests (without geotextile), the failure mode of soft subgrade were found to become general failure mode from local failure mode. Therefore, the bearing capacity of the subgrade increased due to the presence of a geotextile. The porewater pressure within the soft soils increased initially and then decreased with the number of loading cycles. The influence of the types or weights of geotextiles on excessive porewater dissipation is found very minimal. No considerable amount of fines migrated through the geotextiles in the laboratory tests.
Geosynthetics play a very important role in application to waste landfills. They can be used as surface layer, protective layer, drainage layer, barrier layer, as well as for gas collection. This paper introduces how geosynthetics are applied as the components of the cover and the liner systems of waste landfills. Some consideration and important issues are also mentioned for material selection, designing, and construction. In addition, the characteristics of geomembranes are described as well.
LANDFILL HYDRAULIC BARRIER MATERIALS AND METHOD OF EVALUATION BASED ON TECHNICAL EQUIVALENCY
地工合成材的快速發展有一大部份的原因歸諸這些材料在廢棄物掩埋場中的應用。由於法規的制訂直接導致了地工止水膜的廣泛使用，其後許多其他地工合成材料也陸續被引進掩埋場工程中。但是也因為法規的限制，導致了許多新開發的地工合成材料並不容易被立即應用於掩埋場中；主管機關往往必須針對個案進行材料的評估。近幾年來，美國衍生出一套基於技術相當性的評估方式，非常值得借鏡；本文中將予以詳細說明。文中雖僅就掩埋場中最重要的子系統-阻水系統使用的材料為例做詳細的技術相當性評估介紹。但是這一套原則對於其他子系統如滲出水集排水系統(Leachate Collection and Removal System, LCRS)、排氣系統(Gas Collection System)、甚至是每日覆土(Daily Cover)，都同樣適用。
Hydraulic barrier is the most critical component of the bottom lining and final cover systems of modern landfills. There is a wide variety of materials that can be used for hydraulic barriers including synthetic materials made of polymers, natural soils, asphalt, and composites made of some of these materials. The choice of materials has been limited by regulations such that many new geosynthetic products are excluded. Recently, a method for comparing these materials based on technical equivalency has been developed and has been gaining acceptance among the regulatory agencies and the industry. The procedure will be introduced in this paper and will use the hydraulic barrier material as the subject for evaluation. The procedure should also be employed to evaluate other components of the landfill.
The ground freezing technique was used to improve the watertightness and the shear strength of the ground. By transferring the heat in the ground via the brine circulation pipes into the atmosphere, the ground is then frozen. This paper presents the details of ground freezing and the application of this technique to the restoration of the damaged linings of tunnel 2A of Contract CH221 of Taipei MRT.