Date of Award

Fall 2009

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Civil Engineering - (Ph.D.)

Department

Civil and Environmental Engineering

First Advisor

Dorairaja Raghu

Second Advisor

Walter Konon

Third Advisor

Angelo J. Perna

Fourth Advisor

John R. Schuring

Fifth Advisor

William R. Spillers

Abstract

This research discusses the results of experimentation that determines the rates and magnitudes of consolidation and settlement of solid waste materials dependent upon their actual state of biodegradation decomposition and time in place. The state of decomposition of waste is determined by measuring its cellulose plus hemicellulose to lignin ratio ((C + H)/L). The samples were collected from bioreactors, at consecutive time intervals, to simulate states of decomposition.

Each sample was tested in consolidation to determine the value of the primary compression index C' c, the secondary compression index "the inorganic creep rate" coefficient, C' α, and the "initial and tertiary rate of biodegradation decomposition of the mass volume" compression indices Cβ and Cαβ. Gas generated was observed to provide a means to equate observed laboratory time to actual field time. The observed gas volumes generated were compared to calculated theoretical gas volumes determined from a first order decay model based on the USEPA LANDGEM model. The values obtained as part of this research were determined for a loading increment of 2.56 tons per square foot (tsf) for all samples, unless otherwise stated, and indicate that C' c varies from 0.1831 to 0.2445 for the prepared waste samples. An exponential comparison of C' c and the (C + H)/L ratio indicates that the value of C' c decreases with decreasing (C + H)/L ratio. The values for C' α, ranged from 0.0050 to 0.0095 for the tested samples.

The values for C’ α were observed to increase with respect to decreasing (C + H)/L. The value for the coefficient Cβ is 0.0.1470, for Sample A (LT) and 0.0540 for the Humus. The values of Cβ for the waste samples ranged from 0.0150 to 0.1470 and, as expected decreased as (C + H)/L decreased. The values of the Secant Modulus of Biodegradation, (Secantβ) were observed to be directly proportional to the (C + H)/L ratio, varying from 0.0300 to 0.0109. The value for Cαβ is 0.0340 for Sample A (LT) and 0.0235 for the Humus. Graphical relationships between Cαβ and the (C + H)/L ratio indicate that the value of Cαβ ranged from 0.0055 to 0.0340 decreasing as (C + H)/L decreased.

The results indicate that the inorganic and organic portions of primary settlement may be calculated using Terzaghi's theory of conventional soil mechanics and the C' c and Cβ coefficients related to strain and also corresponding to the cellulose plus hemicellulose to lignin ratio, (C + H)/L of the waste material, representing its state of biodegradation decomposition. The secondary settlement related to the coefficient C' α and the tertiary coefficient Cαβ were also observed to be dependent upon the existing state of decomposition of the waste material.

By utilizing the C' c, C' α, Cβ, Secantβ and Cαβ rate values, determined for waste at various values of (C + H)/L, predictions of the settlement remaining under structures or fills at any given time in the future can be estimated. The model was validated by comparing observed settlement to predicted settlement for the Kingsland Landfill located in North Arlington, New Jersey. A methodology to predict the settlement of waste of any composition is also presented.

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