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NUMERICAL ANALYSIS OF DISPLACEMENT OF LATERALLY LOADED PILES SUBJECTED TO DYNAMIC LOADING
(Hawassa Inversity, 2022-10-16) LIDIYA WOLDE DENDIR
In this paper, the behavior of a vertical pile for both free headed and fixed head condition and
batter pile subjected to lateral earthquake load are modeled with finite element software. The
paper attempts to examine the effect of vertical and batter angle on its deflection magnitude with
different pile length and magnitude under earthquake loading. The overall response of vertical
and batter pile subjected to lateral earthquake load are investigated using 3D finite element
method was applied for numerical modeling and plaxis3D software is utilized to evaluate the
lateral displacement of pile. For this analysis, the length of the pile varies between 4m-24m with
4m interval and the batter angle vary 5
0
-250
. The effective pile length (lc) values differentiate
the pile as short and long pile for both free head and fixed head conditions. also the analysis
done on batter pile Two cases were considered; one case considered positive batter pile with
pile length 8m the and two case considers negative batter with pile length 8m. The built-in
material models of the Finite Element (FE) program PLAXIS were used to capture the head
displacement of pile and for the seismic loading a real strong motion record of Hollister
earthquake is adopted largely for its small duration. Dynamic analysis carried out using linear elastic soil material model used for both pile and soil. The analysis indicates that the head
deflection on a pile decrease with increasing pile length because of soil stiffness increase within
the depth for fixed head and free head pile. Short pile has higher deflection than long flexible
pile for both fixed head and free head condition. For the increasing in negative batter angle
decreases the pile head displacement This behavior is due batter pile generally have higher
horizontal stiffness, mainly due to the fact that inclined pile provide partial horizontal resistance
and the upper soil support in a negative battered pile is enormous. For the increasing in positive
batter angle increasing the pile head displacement This behavior is due the soil reaction at the
ground level is zero for positive batter pile
EVALUATION OF SLOPE STABILITY CONDITIONS BY NUMERICAL ANALYSIS, A CASE OF OTOLO-SAWLA ASPHALT ROAD PROJECT, SOUTHERN PART OF ETHIOPIA
(Hawassa University, 2020-10-08) NATNAEL BEREDED BAYOU
Slope instability related issues in engineered, as well as natural slopes, are common challenges
to geotechnical enginers. Due to the slope instability, so many associated risks arise around the
cut slope so that it is advisable to analyze the slope stability ahead of excavation. Once slope
failure occurs, traffic flow gets obstructed and which ultimately limits the road serviceability
level impacting the economy. This thesis presents the investigation, analysis, cause
identification, and remedial measures for failed slope and checks stability of the existing slope.
Seven cut slope related instability locations were selected along with Otolo-Sawla Asphalt Road
Project located in the Southern part of Ethiopia. In this thesis, disturbed samples were taken
from a test pit dug in the slope section by hand excavation. In the case of existing slope locations,
three samples were taken based on the slope angle and the material forming the slope through
field observations. Laboratory tests were conducted to determine the index properties and
engineering properties of the soil-forming the selected slope sections. The main objective of
this thesis was to investigate slope stability conditions of the Otolo-Sawla asphalt road project
using a numerical method considering selected slopes at varied geological and geographical
locations. A suggestion of remedial measures to stop further failure of the slope section can be
analyzed by modeling with commercial software PLAXIS 2D. Under this thesis, the factor of
safety for the identified slope failure was determined using Finite Element software (PLAXIS
2D) based on the strength reduction approach. Based on the analysis the causes for failed slopes
were identified as poor slope material, excessive slope height, and high groundwater levels. In
this thesis the order of sensitivity of factors affecting the slope stability obtained as φ>H>c>γ
>k >E>μ. A stability check for the existing slopes was carried out and was found slightly stable.
On the results from the analysis, the failed slope sections should be reconstructed with a slope
angle less than 50% and an adequate drainage system should be provided. Existing slopes near
the failed slopes are prone to failure because of similar soil properties and groundwater
influence. The provision of geosynthetic for adequate drainage has been recommended as a
remedial solution to avoid failure of the existing slopes near the failed slopes.
EFFECTS OF WASTE PLASTIC AS PARTIAL REPLACEMENT OF BITUMEN AND USE OF COFFEE HUSK ASH AS MINERAL FILLER FOR THE PERFORMANCE OF HOT MIX ASPHALT
(Hawassa University, 2021-10-18) NAHUSENAY MULUKEN TESSERA
Bitumen properties and external factors such as climate and traffic volume conditions
govern hot mix asphalt pavement performance. Bitumen is viscous-elastic naturally and very
sensitive to temperature, which influences its rheological properties. Flexible pavements are
linked to extreme high-temperature causing rutting and fatigue cracking. Pavement distress
shortens service life and increases maintenance costs. This research focused on improving
pavement resistance to distresses by modifying the rheological properties of bitumen and
using alternative fillers such as coffee husk ash (CHA). In this study, two phases were
utilized. The first phase was collecting samples, and the second contained three sub-phases.
To design a material quality test, the first step was to develop a Marshal mix design and
three types of mixtures which was a mixture of normal HMA with SD filler, with CHA filler,
and a combination of CHA filler and 3, 6, 9, and 12% PET plastic. Rolling thin film oven
test (RTFO) and Dynamic shear rheometer are used to analyze the rheological properties
of asphalt binder (DSR). Finally, for evaluation purposes, results of 3D-Move analysis
software for moving vehicles under various loads and speeds were obtained. AST result
shows that at 6% PET containing bitumen has better LVER when compared with original
bitumen that changes from 2.49, 23.0, and 64.7% to 7.5, 50.2, and 87.1% at a temperature
of 21.1, 37.8, and 54.40C, respectively. On the other hand, PG determination of the original
binder has no variation at 3% PET but improved from PG 58 to PG 64 and PG 70 when the
bitumen is modified at 6 and 9% PET plastic. From MSCR criteria, test result at 9% PET
modified binder can be used for heavy traffic and approaches to very heavy traffic compare
with 0, 3, and 6% PET plastic and a significant improvement for rutting resistance at a test
temperature of 700C. The penetration and ductility value decrease with softening point
increase as the PET content increases from the conventional test result. Furthermore, from
the marshal test, CHA filler is a better performance of HMA mixture compared with SD
filler. At 6.8% optimum PET plastic higher stability (15.9KN) and density value
(2.268g/cm3
) and lower flow (2.96mm), VMA (14.83%), and VFA value (73.01%) as
compared with unmodified bitumen of 14.30KN, 3.5mm, 2.256g/cm3
, 15.62%, and 75.06%
value respectively at 4% air void provided. The analysis 3D-Move software showed that
asphalt binders with higher PET plastic content have the best performance as the stiffness
of the asphalt mixes would increase with the addition of PET plastic. Therefore, the
evaluation showed that partial replacement of PET plastic with the range of 6 to 9%
improves the rheological properties by stiff the binder and rutting resisting performance of
binders at high-temperature range and increasing the LVER has a better performance of
HMA mixture
ASSESSMENT OF LEAN CONSTRUCTION PRACTICE IN ETHIOPIA USING ANALYTICAL HIERARCHY PROCESS METHOD
(Hawassa University, 2022-10-22) MULUKEN FIKADU AKEWAK
The performance of the construction industry is hampered by physical and non-physical
waste. Hence, the requirement to embrace the implementation of Lean Construction (LC)
practices that encompasses working culture, tools, and concepts to maximize value
whereas additionally minimizing all kinds of wastes. The aim of this thesis is to assess the
implementation of lean construction in Ethiopia, specifically in sidama region public
projects. The paper investigates the implemented lean construction techniques and tools
and identifies the benefits of implementing lean construction. In addition to this, the
barriers to implement and critical success factors for improvement of lean construction are
prioritize. The study was conducted using relative importance index (RII) and analytical
hierarchy process (AHP) on Microsoft excel. Both qualitative and quantitative research
approach is adopted to address research. The primary data were gathered from project
managers, site engineers and site supervisors through questionnaire survey and interview
and secondary data obtained from journals and research proceedings. The result obtained
from respondents were correlated and discussed in detail. The findings revealed that pursue
perfection, create smooth flow in process, allowing customer to pull, map the value stream
and identify customer value are most significant lean techniques and last planner system,
5s, concurrent engineering, just in time and daily huddle time are the most significant lean
tools implemented in construction projects. Similarly, increased productivity, reduce waste
and production cost, eliminate all non-value adding activities, continuous improvement and
reduce project time are top five benefits of implementing lean in descending order
according to their RII value. The twenty five barriers to implement lean are categorized in
to seven groups and prioritized using AHP. The result showed as lack of top management
support and commitment, fragmentation and subcontracting nature of industry, resistance
to change, incomplete and inaccurate design and influence of traditional management
practice are most significant barriers based on their global weight. Also, from sixteen
critical success factor, management commitment and involvement, understanding of
technical requirements in lean, employee morale and motivation, strategy planning and
training employees are most significant factors according to their global weight. Finally,
the research concluded that lean implemented in Ethiopia with some barriers and
recommended project managers to encourage improving its implementation in project site.
CHARACTERIZATION OF COHESIVE SUBGRADE SOIL FOR FLEXIBLE PAVEMENT DESIGN (IN CASE OF WEZEKA-KONSO ROAD)
(Hawassa University, 2019-10-22) MULUGETA REGASSA YIMAM
Road transport has a vital contribution for a nation development. Road has to be designed in a
way that it can function in all season of the year, this could be achieved if the road is paved
and the structural elements of the pavement is well designed. In general pavements are
classified as rigid and flexible pavements. In rigid pavement loads are carried by the concrete
itself thus the design requirement is the flexural strength of the concrete whereas in flexible
pavement, the intention of the design is to reduce the deformation of the subgrade under a
certain loading condition. Thus, flexible Pavement design needs proper material
characterization so that failures in structural as well as functional could be mitigated. The aim
of this study is characterization of cohesive subgrade soil for flexible pavement design in case
of Wezeka – Konso road, Ethiopia. Identification of the Physical properties and classification
of the soil was done according to AASHTO criteria. Resilient modulus was predicted from
unconfined compressive strength. Additionally, a method has been developed for prediction of
resilient modulus from unconfined compressive strength and index properties of soil. For both
prediction models Microsoft excel was used to conduct the statistical analysis. The soils used
for this study were low to medium plastic fine-grained soils. According to AASHTO soil
classification system the soils were group in A-4, A-5, A-6 and A-7-5 categories. Statistical
analysis shows that the relation between resilient modulus and unconfined strength was linear
correlation. For this correlation the coefficient of determination value of R2 = 0.83 was
obtained. For the second model which is prediction of resilient modulus from unconfined
compressive strength and index properties the correlation was multilinear with coefficient of
determination R
2=0.87. Due to the inclusion of index properties in the second model a better
correlation was observed.