The initial behaviour of domestic refuse in a large-scale test

摘要

The nature of refuse landfill, particularly its very poor engineering properties and the major health and safety issues associated with gas production, has so far largely prevented the reuse of recent refuse landfill sites for purposes other than agriculture or occasionally amenity use. Rates of settlement and waste stabilisation are extremely important for restoration schemes, modelling existing and future landfill engineering, aftercare management and monitoring, reuse for other purposes (sports fields, amenity, biodiversity schemes). As waste stabilisation processes may extend up to many decades, it is vital to develop improved methods of dealing with waste. Inhibited gas production from saturated waste or excessively dry waste will delay the stabilisation of a landfill and may severely limit its potential for reuse. Re-circulating leachate is a means of ensuring the waste mass remains in a partially saturated state, promoting an increased and uniform rate of biodegradation and gas production over the full depth of the waste mass, as well as resulting in higher effective stresses within the waste. These factors play an important role in determining the rate and magnitude of volume reduction and hence waste settlement. It is essential that reliable data on fill behaviour is gathered in order that biodegradation/settlement models can be developed to aid the effective management of landfills and facilitate their early and safe reuse for future building or amenity purposes. This paper describes a large scale test which is currently being carried out to identify the effect and benefits of leachate re-circulation and which forms part of a major project to study the long-term behaviour of refuse landfill. The recirculation test is being carried out by BRE in a sealed test pit containing some 96 cubic metres of domestic refuse. Surface and subsurface settlement, in situ stresses, temperature, leachate levels and leachate chemistry are being monitored. Gas production is a critical element of the degradation process, and forms an important part of the experiment. A system has been installed to monitor and control gas extraction. The test represents a unique and detailed study of the behaviour of a representative volume of refuse which is considerably larger than is possible in large-scale laboratory apparatus but with all the advantages of complete cor trol of the test environment. The test began in November 2000. This paper presents the early findings and the proposed future work.