Restprodukter i tätskikt för deponier med anrikningssand: Utvärdering av grönlutslam blandat med flygaska/anrikningssand
Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
The mining industry and pulp and paper mills generate annually a large quantity of waste materials (Wik et al. 2003). Landfilling has for a long time been the most widely used method for these wastes. These waste products can cause considerable environmental problems; large amounts of pollutants are collected in a small area and can be leached out and contaminate the surrounding environment. Deposition of tailings from the mining industry occurs today in two ways: soil cover or water cover, which can both be expensive and difficult to perform. The most common method is water cover when tailings and water are directly pumped from the mill into a sand reservoir where the tailings then sediment and are stored. (Karltorp, 2008) In a closer study of the method "land cover", there are a number of different test performed. In one field test a mixture of green liquor dregs (GLD) and stone dust was used as a barrier layer (NCC Roads, 2011). GLD was used as a barrier material and stone dust was used to increase the shear strength in the barrier layer. GLD is one of the major waste products from pulp and paper mills and can act as a barrier material to: prevent infiltration of oxygen, reduce the water flow and to buffer against acidification. The aim of this study is to investigate the possibilities of using a mixture of GLD and fly ash/tailings as a barrier layer for mine waste (tailings). If GLD is going to be used as a barrier layer, the geotechnical properties must be improved by adding a strength-enhancing material (fly ash/tailings). A schematic picture of a landfill of tailings with a soil cover can be seen in Figure 1. To investigate the possibility of using GLD and tailings/fly ash as barrier layer the following experimental tests were performed: permeability test with constant pressure head, freezing test followed by permeability test, strength test (unconfined compression test), pycnometer test, compaction test and leaching test. GLD directly from the factory has a high water content which leads to a slightly higher permeability (10^-8 m/s) than the guideline value for a barrier layer (10^-9 m/s). If the industrial processes that generate GLD should not be changed a possible solution is to use GLD that has been stored in landfills. GLD which has undergone a consolidation process, pressure under a given time, is compressed and the water content and permeability are decreased. In the performed strength tests the obtained shear strengths was “very low” (10-30 kPa) when only using GLD and mixtures of tailings and GLD. Thus, tailings directly from the mill are not recommended as a potential strengthenhancing material. When fly ash (10%) is added a significantly higher shear strength (about 50-95 kPa) is obtained. The results also show that hardening properties of fly ashes have a clear effect. The samples stored for 3 months (about 90-265 kPa) instead of 1 month (about 50-95 kPa) gave up to 2-3 times higher shear strength. Shear strengths between 150 and 300 kPa is classified as “very high”; thus fly ash is a potential material for increasing the strength of the GLD. According to leaching tests carried out on GLD, there are signs of positive properties even after the buffering capacity is finished. This is because GLD shows a tendency to bind metals. When using GLD as a barrier layer, the geotechnical properties (permeability and shear strength) can be improved by using GLD from landfills and blend in fly ash.
Place, publisher, year, edition, pages
2011. , 110 p.
Teknik, restprodukter, grönlutslam, anrikningssand, flygaska, enaxiellt tryckförsök, lakningsförsök, permeabilitetförsök, frysförsök, pyknometerförsök, lackningsförsök, permeabilitet, skjuvhållfasthet
IdentifiersURN: urn:nbn:se:ltu:diva-50931Local ID: 8243e703-45a4-4fbf-bfa6-c33bdbbe0506OAI: oai:DiVA.org:ltu-50931DiVA: diva2:1024294
Subject / course
Student thesis, at least 30 credits
Civil Engineering, master's level
Maurice, ChristianPousette, KerstinMäkitalo, Maria
Validerat; 20110920 (anonymous)2016-10-042016-10-04Bibliographically approved