Because the geosynthetics can serve the purposes of drainage, barrier, reinforcement, separation and filtration, it is widely applied on the geoenvironmental related engineering. Through introducing the landfill structures, this paper presents the common features of geoenvironmental engineering. The capabilities of some geosynthetic products are also briefly introduced. The applications and selection of suitable geosynthetic products to special engineering requirements are presented. Finally, some important concerns about the design, material, testing, and construction on the application of geosynthetics on geoenvironmental engineering are introduced.
The refuse received by MSW landfill consists of material in various physical and chemical properties and different shapes. The engineering properties of refuse change with time and make it a challenging endeavor to correctly predict and analyze the long-term deformation as well as stability of sanitary landfill. The strength of refuse usually decreases with time and affects stability of landfill whereas most of the engineered fills become stable with time. The long term stability of sanitary landfills is usually jeopardized by excessive fills of refuse, inadequate design, or lack of proper management after closure. A slope failure case of an old MSW landfill is introduced with respect to the long-term stability of sanitary of landfill.
The amount of settlement is an important factor regarding the design on landfill cap system, biogas recovery system, leachate collection system, and rehabilitation of enclosed landfills. However, the settlement behavior of landfill is not fully understood nowadays because the waste material is heterogeneous and biodegradable, as well as the local effects of surrounding environment and landfilling operation. Besides, in practice, there is no appropriate model to predict the settlement of landfill. In this study, both data of published landfill settlement and compression tests of waste material are collected and analyzed for the quantitative study of the characteristics on the landfill settlement behavior and its effect factors. Besides, three prediction models are introduced and discussed. Finally, two cases about the engineering problem that is induced by the settlement of closed landfill were discussed to illustrate the importance and essentiality to estimate the settlement of landfill.
The hydraulic barrier material most often used in landfills are compacted clay, geosynthetic clay liner, and geomembrane. In the past, most of the researches have focused on the ability of these barrier materials to retard the migration of water. However, compacted clays and geosynthetic clay liners tend to crack due to wet/dry cycles. In this research, the effect of desiccation on the air permeability of hydraulic barrier in cover system was studied. The results show that both compacted clays and geosynthetic clay liners may crack when they are subjected to a hot and arid environment. Furthermore, a soil cover of 0.5 m may not be thick enough to prevent the development of the cracks. It is therefore suggested that the barrier layers in cover system of landfills in arid or semi-arid area should include geomembrane to prevent the emission of landfill gas.
Many soil and groundwater contaminated sites have been reported in Taiwan in recent years. Consequently, the land value and the local residential health near the sites are seriously threatened. Taiwan EPA promulgated the Soil and Groundwater Remediation Act in 2000 to take actions on these contaminated sites. This article briefly describes the pollution sources, the characteristics of contamination, investigation methods, remediation work, and case studies so that the engineers in other professional areas can understand this new engineering field.
This research was conducted using laboratory experiments to observe the piling effect on the aqitard leakage. Test results showed that clayey lenses present in a sandy stratum tend to drop the vertical permeability from 10-3cm/sec to 10-6cm/sec. The vertical permeability appears to be governed by the interbedded clayey lenses even their thickness are negligible. However, when pile was penetrated through the clay and no matter what the permeants were used (water, gasoline, or dichlorethane); the vertical permeability (k) values all increased by orders of 3 to 4 magnitudes. Parameters that affect the k values are clay thickness (t), pile diameter (D), and pile penetration length beyond the clay (Lo). The k values increased with decreasing t/D or increasing Lo/t. The pile penetration appears to push and drag appreciate amount of upper sand into the clay layer, develop a preferred flow pathway, and thus cause the permeability to increase. However, such effect was diminished when t/D>1.7 or Lo/t
Combustion bottom ash is a residue produced by the mean of incinerating municipal solid waste at trash incineration. The municipal waste bottom ash has several characteristics, such as light specific gravity, high absorptivity, heavy metal, including copper, lead, chromium, and zinc, etc., high basicity, and high concentration of chloride, and so on. In consideration of sophisticated technology of bottom ash recycling and practical applications of geotechnical engineering in Taiwan, recent studies of bottom ash recycling are collected in this paper including that bottom ash replaces for natural materials in base layer of road and application of CLSM. Hopefully, due to this introduction of bottom ash recycling, a decrease in loss of natural materials and perpetual operation of natural resources could be achieved.
This paper presents ground improvement with Superjet-Midi (SJM) method. The procedure of construction and engineering properties of the soilcrete are introduced. The SJM method was first adopted in Taiwan for the construction of Taipei Rapid Transits Systems. The jet-noise monitoring technique was first used to identify the diameter of soilcrete column formed in the ground. Cylindrical specimens were drilled from the site and tested in the laboratory. It is found that the core recovery of the samples varies from 90% to 99%, which is higher than the design requirement of 80%. RQD of the specimen varies from 79% to 97%. The uniaxial compressive strength qu of the sandy soilcrete varies from 3.65 to 22.6 MPa, which is greater than the design requirement of 3.0 MPa. The qu for clayey soilcrete varies from 1.88 to 10.0 MPa, which is higher than the design requirement of 1.0 MPa. The relationship between the strength qu and stiffness E50 of the soilcrete can be described with the formula E50 = 100qu ~ 300qu proposed by the JSG Association (1986). The permeability of soilcrete changes from 3.2 to 6.6 × 10-7 cm/sec, which is significantly lower than the design requirement of 10-5 cm/sec.