Geotechnical behaviour of sanitary landfill

The geotechnical behavior (Permeability, Shear strength and Consolidation) of sanitary landfills varied with time as a result of decomposing reactions of solid waste within landfill, affected by the chemistry of pore fluid and initial compaction effort. The following conclusions could be drawn:(a) PerJlleabilitv1. The permeability of new MSW is higher (about four times) than the permeability of the intermediate MSW which in turn is higher (about six times) than the permeability of the old MSW at the same initial compaction (20 % of standard proctor) and after the same maturation time (28 week).2. Recirculating the old leachate to the top of the new waste decrease the permeability of the new waste to different values (from 5 % to 40 % of its value if there is no recirculation) based on the initial compaction and the maturation time.3. The permeability of the new MSW initially compacted at lower compaction effort (20% of standard proctor) is much higher (about 1000 times) than its permeability ifit is initially compacted at higher compaction effort (100% of standard proctor).4. The permeability of the intermediate MSW initially compacted at lower compaction effort (20% of standard proctor) is higher (about 250 times) than its permeability if it is initially compacted at higher compaction effort (100% ofstandard proctor).5. The permeability of the old MSW initially compacted at lower compaction effort (20% of standard proctor) is higher (about 50 times) than its permeability if it is initially compacted at higher compaction effort (100% of standard proctor).6. The permeability of the new MSW initially compacted at lower compaction effort (20% of standard proctor) is higher (about 500 times) than its permeability if it is initially compacted at higher compaction effort (100% of standard proctor) instead of 1000 times if there is no recirculation of the old leachate.(b) Shear StrengthI. The shear strength of new MSW is about 85% of the shear strength of the intermediate MSW and is about 75% of the shear strength of the old MSW at the same initial compaction and at the same maturation time.2. Decomposing reaction of solid waste that occurs within the sanitary landfill with time, changes the values of shear strength parameters (C & <p). The solid waste cohesion increases and theinternal angle of friction decreases with time at certain value of initial compaction effort.3. Increasing initial compaction effort (from 20% to 100%) increases the value of internal angle of friction <p to about 200% of its initial value and slightly decreases the values of solid waste cohesion.4. Recirculation of old leachate on the new solid waste landfills changes the shear behavior of that waste. The waste cohesion increases by about (100 - 200) % and the internal angle of friction <p decreases by about (20 - 30) %, at certain time at any value of compaction effort.(c) COllsolidatioll1. New MSW include voids ratio higher than intermediate MSW that in turn has void ratio higher than old MSW. It ranged from 300% to 500% of the void ratios of fine soils. 2. New MS W has a compressibility coefficient higher than intermediate MSW that in turn has compressibility coefficient higher than old MSW.3. New MSW has a volume change coefficient higher than intermediate MSW that in turn has volume change coefficient than old MSW.4. New MSW has a compreSSiOn index higher than intermediate MS W that in turn has compressiOn index higher than old MSW.5. New MSW has a vertical settlement higher than intermediate MSW that in turn has vertical displacement higher than old MSW.6. The above consolidation factors and parameters are grater than of soils by about (3 times) its ordinary values for soils.7. The chemical behavior of leachate changed during the test period.Chloride, sulfate and (Chloride/sulfate) ratio, some of the controlling elements from the chemical analysis are increased it the new waste stage of decomposition gives an indication about how aggressive the environment around foundations is. This is important in the foundation concrete mix design and construction of8. For new solid waste the PH number increases with time towards the neutral state in the acidic side. Typical behavior of intermediate leachate but towards the alkaline state. But in old waste it shows a constant value of PH number indicates alkaline environment, this is why the bacterial activities are stopped in the old ages.8.2 ReCOIIUllelltlatiolls(I) We should pay enough attention to the initial compaction of the refuse during its placing in the landfill to minimize the permeability and increase shear strength through landfill as well as improve its geotechnical properties. Also, much awareness should be practiced regarding the daily cover to control the quantities of water that enter a landfill during the period the landfill is being filled. At that stage the new refuse has a higher permeability enables the flowing water to go through the landfill quickly and increase the amount of leachate.(2) 011 olle halld, we must utilize proper provisions within both the design and construction of landfill slopes, cover, leachate collecting system to compensate the significant settlement occurs with fill age. In