This study models the compaction of soil by a vibratory roller compactor and examines changes to current designs that may provide more efficient compaction. The modeling of the soil differs from previous analyses of the compaction process in its use of a distributed-parameter characterization of the soil mass and in the application of nonlinear constitutive relations that predict the continuous evolution of residual stresses in the soil. The model was used to determine whether compactor performance might be improved by changes in the forward speed of the compactor or by redistribution of the weight of the frame. No improvement was found to occur. The model was also used to estimate the effects of varying the frequency of vibration to match the evolutionary changes in soil properties during compaction. Hardly any improvement over operation at constant frequency was indicated, but this finding may reflect the tendency of the model to underestimate the rate of stiffening in the soil. / Master of Science

The main purpose of this study was two-fold: 1. To show any existing correlation between OBR and UCS tests. 2. To show variation in UCS due to various methods of curing Using a Harvard miniature apparatus, compactive curves were determined for standard AASHO compactive effort for 0, 5, and 10 percent lime. From these curves the moisture contents to be used for strength tests were determined. These were dry of optimum (optimum -6 percent), optimum, and wet of optimum (optimum -̷6 percent). CBR specimens were fabricated at the above moisture contents for 0, 5, and 10 percent line. In all, nine samples were prepared. This was repeated using the miniature apparatus for the unconfined compression test. Six samples were prepared for each test condition. Two of these were tested as molded, two after damp curing (four days 67ºF), and two after oven curing (two days 120ºF). The results of this study indicated the following: 1. Lime increases the strength of the soil. This effect was very significant on the dry side. 2. Up to five percent addition of lime produced little increase in strength. This value may be considered as a fixation value of lime for this soil. 3. Curing increased the UCS and CBR of lime-treated soil. Accelerated oven curing 120ºF for two days given significant increase in strength, especially with 10 percent lime. 4. No definite conclusions could be derived between as molded CBR and as molded UCS, between soaked CBR and damped cured UCS, and between soaked CBR and oven cured UCS. / Master of Science

Soil compression is a topic of increasing importance in the evaluation of foundation sites for the heavy, rigid structures being founded upon them. The first analytical approach to compressive behavior in soil was presented by Terzaghi in the 1920's. Since that time, his consolidation theory has formed the general basis for prediction of soil compressibility under load. Compressive behavior not explained by Terzaghi’s assertions is known to occur in soils. These aberrations may be broadly classified into three categories: (1.) Initial or Elastic Deformation, (2.) Secondary time effects, and (3.) Compression rate discontinuities not attributable to the exuding of water from the soil skeleton. This study attempts to explain such anomalistic behavior in terms of electrochemical characteristics of the clay-water system observed subsequent to acceptance of the consolidation theory. The proposed mechanistic model of soil compression amends to Terzaghi’s considerations the internal energy consumed in the generation and degeneration of electrochemical bond. Such bond is the result of the electrochemical charges on clay mineral particles coupled with the strong polarity of water molecules. Under the influence of these electrochemical forces, each water molecule has a unique position and orientation commensurate with the condition of minimum potential energy. For relative movement to occur among clay particles or within the molecular water structure, electrochemical forces must be overcome at the expense of the clay-water system's internal energy, thereby creating an intergranular bond of structural water. The bond process model considers soil compression to be an aggregate response of bond creep, bond rupture, and bond formation, which may or may not be joined by consolidation as a controlling factor. The model illustrates initial compression and compression rate discontinuities as bond creep/bond rupture manifestations and secondary compression as the outgrowth of bond formation. Implications are also made which attribute compression time-lag as much to the rheologic properties of the soil skeleton as to resistance to water flow as asserted by Terzaghi. The findings of an experimental program are presented to substantiate the proposed model. Included in the findings are the results of three individual studies. The first study involves the visual inspection of compression curves from a representative group of undisturbed samples from throughout the United States. In keeping with the implications of the bond model, stress history appears to be a primary factor in control of soil compression and in the motivation of anomalous compressive behavior. Secondly, the influence of temperature upon compression characteristics was studied in detail. The findings illustrate the effect of temperature action on the colloid system which in turn affects bonding energies. Temperature influence is considered to be representative of the effect of various parameters on the distribution of net electrochemical potential in the colloid system. The final study entails determining the action of soil plasticity on soil time response. Comparison of compression curves from soils of similar characteristics, with the exception of plasticity, suggests that plasticity is coupled with permeability in controlling compression rate. / Ph. D.

M.S.

For the past ten years certain experiment stations have conducted studies dealing with soil and water losses under a wide range of conditions, but no study has been conducted on plots under actual field cultural conditions. These investigations have been very valuable in that they have revealed much needed information but they have added very little knowledge of plot technique under field cultural conditions. The size of the experimental plots for these studies has varied considerably from the small indoor laboratory plot to the complete watershed study. The indoor laboratory plot would exist under artificial conditions and could add little to methods and technique of the field plots, whereas the watershed investigation would take into account many factors not effecting field conditions. It is evident that a plot which would permit conduct of studies on the effect of fertilizer on soil and water losses under field conditions would be valuable. Such investigation is therefore undertaken in this thesis for a Master Degree. lt is believed that the information obtained from this investigation will have special value because it is the first of its kind to be obtained on Virginia soil and because the experiment will furnish needed data regarding the measurements of soil and water losses under the special field conditions due to fertilizer treatment. Objects In order to permit a more complete study of soil erosion and its causes some type of portable field plot is needed. Thus the objects of this investigation are as follows: (1) To develop and propose technical methods for studying soil and water losses on plots under field cultural conditions. (2) To test the practicality and usefulness of the methods developed by conducting studies on soil and water losses from plots of different fertilizer treatments. / M.S.

The use of tensile reinforcement to increase the tensile strength and shear strength of soils has lead to many new applications of reinforced soil. The use of such reinforcing in embankments and foundations over weak soils is one of the most recent applications of this technology. The studies conducted were concerned with the development of and application of analytical techniques to reinforced soil foundations and embankments over weak soils. A finite element computer program was modified for application to reinforced soil structures, including consolidation behavior of the foundation soil. Plane strain and axisymmetric versions of the program were developed and a membrane element developed which has radial stiffness but no flexural stiffness. The applicability of the program was verified by comparing analytical results to case histories of reinforced embankments and to model studies of reinforced foundations. A simplified procedure for computing the bearing capacity of reinforced sand over weak clay was developed which is more general than those previously available. Good agreement with available experimental results was obtained, providing preliminary verification of the procedure. Extensive analyses were made of a reinforced embankment successfully constructed with no sign of distress, and of two reinforced embankments constructed to failure. These analyses showed that good agreement can be obtained between measured and calculated reinforcement forces, settlements, and pore pressures for both working and failure conditions. The analyses further show that the use of the finite element method and limit equilibrium analyses provide an effective approach for the design of reinforced embankments on weak foundations. / Ph. D. / incomplete_metadata

Soil stabilization is a widely used technique in the field of geotechnical engineering for a wide range of applications. Traditional stabilizers such as cement and lime, although very efficient, are not environmentally friendly as they leave major carbon footprints, therefore the demand for sustainable stabilization methods is escalating. This research investigates the potential of two different polymers e.g., a biopolymer derived from organic source, and an inorganic commercially manufactured polymer, as viable alternatives for soil stabilization. The current study focuses on exploring the efficacy of polymers stabilized soil in improving the engineering or geotechnical properties such as plasticity, compressibility, shear strength, and stiffness behavior.The research methodology involves using locally available high plastic clay for stabilization using two different types of polymers and performing laboratory experiments to analyze the strength parameters of the stabilized soil. Xanthan Gum (XG) is a biopolymer which is being studied is used in the percentages of 0.5%, 1.0% and 1.5% by dry weight of soil mass to understand the mechanism of biopolymer-soil interactions and to conclude optimum percentage suitable for stabilization in terms of technical and economical value. Similarly, Soiltac (ST) a vinyl copolymer inorganic polymer is used in 1.5% of dry mass of soil (optimum dosage as per previous literature) to compare its effectiveness with that of Xanthan Gum. After the determination of Atterberg limits and Optimum Moisture Content (OMC) and Maximum Dry Density (MDD), the samples were subjected to tests such as Unconfined Compressive Strength (UCS), Ultrasonic Pulse Velocity (UPV), Resilient Modulus (RM) test and Consolidation test. The prepared UCS samples were cured for 0, 7, 14, and 28 days in open air condition before performing test on them. Atterberg limits test on untreated Carbondale Soil were conducted to classify the soil as CH (Clay with high compressibility) type as per USCS (Unified Soil Classification System) classification. While tests on treated sample showed significant increasement in Liquid Limit (LL), slight increment in Plastic Limit (PL), thus quite surge in the Plasticity Index (PI) with increase in XG percentage in the soil. UCS value increased with the increase in percentage addition of XG. Also, UCS results from both untreated and polymer treated samples showed increase in compressive strength with increase in curing period. UCS value increased from 417.75 psi to 490.24 psi, 504.05 psi, and 542.91 psi for 0.5%, 1.0%, and 1.5% XG addition, respectively. This increase in UCS value was 17.35%, 20.66%, and 29.96% for the corresponding XG concentrations. The treated samples had a significant increase in the UCS for all the curing period in comparison to their respectively cured untreated sample. The percentages increase in the UCS for 1.5% XG sample in comparison to untreated sample cured for the same period is 6.45%, 59.57%, and 29.96%, respectively for 7, 14 and 28 days of curing. However, for the zero-day test, the UCS of 1.5% XG stabilized sample was found to be less than the zero-day untreated sample. With the addition of ST polymer, the UCS value increased for all the curing period while comparing with the UCS of untreated soil for the same curing period. The UCS of the ST treated soil increased from 58.56 psi to 467.367 psi when cured for 0 and 28 days which is an increase of 698.1 % i.e. 7 times the strength at 0 day. When UPV (Ultrasound Pulse Velocity) tests were compared with the UCS value for the same sample, the result showed that the higher UPV value corresponded to the higher UCS value. This relationship was supported by the high degree of correlation between the two measurements. The consolidation test showed that the Compression Index (Cc) of XG stabilized soil decreased as the percentage of XG added increased. Cc decreased from 0.2795 for pure Carbondale Soil (CS) to 0.2003 for 1.5% XG addition which is a drop of 28.33%. Likewise, Cc decreased by 3.0% and 19.33% for 0.5% and 1.0% XG doses respectively. The primary aim of this study is to simplify the understanding of the Resilient Modulus (RM) test, which yields vital data for pavement design. The efficacy of inclusion of stabilizer was further substantiated by RM testing which confirmed the enhancement of soil resilient qualities compared to the untreated soil. The RM values exhibited a growing trend, indicating an enhancement in the soil's stiffness and capacity to endure repetitive loads. This attribute is extremely important for applications such as the construction of pavements and foundations that are subjected to dynamic loads. The samples containing 1.0% XG showed significant increases in their RM values. Specifically, the RM values increased by 18.5%, 40%, and 39.5% after being cured for 7, 14, and 28 days, respectively, at a confining pressure of 6 psi. Similarly, the RM for the case of ST ranges from 15227.60 psi for 0 days of curing and 2 psi of confining stress to 45375 psi for 28 days of curing and 6 psi of confining pressure. The performance of ST against XG is higher.

Thesis (M. Phil.)--University of Hong Kong, 1993.

Thesis (M.Phil.)--University of Hong Kong, 1993. / Also available in print.

by Leung, Yu-fai. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1992. / Includes bibliographical references (leaves 167-178). / abstract --- p.ii / acknowledgements --- p.iv / table of contents --- p.vi / list of tables --- p.ix / list of figures --- p.xi / list of plates --- p.xiii / Chapter CHAPTER I --- introduction / the problem --- p.1 / The Country Parks of Hong Kong --- p.1 / Resource Impacts of Country-Park Recreation --- p.3 / Trail Degradation --- p.4 / objectives of the study --- p.5 / scope of the study --- p.6 / Chapter CHAPTER II --- literature review / introduction --- p.8 / research approaches --- p.9 / physical degradation on trails --- p.11 / Compaction / Widening and Incision / Erosion --- p.16 / FACTORS CONTRIBUTING TO TRAIL DEGRADATION --- p.17 / Use Characteristics --- p.19 / Environment --- p.20 / RECREATION IMPACT STUDIES IN HONG KONG --- p.21 / Chapter CHAPTER III --- study area / introduction --- p.24 / the pat sin leng country park --- p.24 / "Topography,Geology and Soils" --- p.25 / Climate and Vegetation --- p.29 / Recreational Use and Management --- p.31 / the pat sin range trail --- p.35 / Chapter CHAPTER IV --- research methodology / introduction --- p.41 / research design --- p.41 / hypotheses --- p.43 / SAMPLING SCHEME --- p.44 / VARIABLES INCLUDED IN THE STUDY --- p.46 / FIELD MEASUREMENTS --- p.49 / Degradation-Indicator Variables --- p.49 / Site Condition Variables --- p.58 / LABORATORY ANALYSIS --- p.63 / DATA MANIPULATION AND ANALYSIS --- p.65 / Chapter CHAPTER V --- SITE AND DEGRADATION CONDITION OF THE PAT SIN RANGE TRAIL / INTRODUCTION --- p.67 / SITE CONDITION OF THE TRAIL --- p.67 / Parent Material --- p.67 / Topography --- p.72 / TREAD SURFACE MATERIAL --- p.80 / COMPACTION OF TRAIL TREAD --- p.82 / MORPHOLOGY OF TRAIL TREAD --- p.90 / Tread width --- p.91 / Incision Depth --- p.94 / Tread Cross-Section Area --- p.96 / Multiple Treads --- p.96 / Other Morphology Variables --- p.98 / OVERALL EVALUATION --- p.98 / Other Evidence of Degradation --- p.98 / Summary Rating --- p.101 / REMARKS --- p.106 / Chapter CHAPTER VI --- ENVIRONMENTAL INFLUENCES ON TRAIL DEGRDATION / INTRODUCTION --- p.107 / BRANCHING EFFECT OF TRAILS --- p.108 / PARENT MATERIAL --- p.112 / Parent Rock --- p.112 / Soil Properties --- p.115 / LOCATIONAL FACTORS --- p.120 / Aspect --- p.120 / Slope Steepness --- p.124 / Trail Position on Slope --- p.136 / OVERALL EVALUATION --- p.145 / Chapter CHAPTER VII --- MANAGEMENT IMPLICATIONS / INTRODUCTION --- p.151 / MANAGEMENT CONSIDERATIONS --- p.152 / THE CASE OF PAT SIN RANGE TRAIL --- p.153 / MONITORING TRAIL USE AND IMPACTS --- p.159 / Chapter CHAPTER VIII --- CONCLUSION / SUMMARY OF FINDINGS --- p.162 / LIMITATION OF THE STUDY --- p.164 / SUGGESTIONS FOR FUTURE RESEARCH --- p.164 / BIBLIOGRAPHY --- p.167 / APPENDIX / DESCRIPTIONS OF SELECTED DEGRADED SITES --- p.179