The master's thesis of researcher Hussein Sahm Jassim was discussed at the College of Engineering, University of Basra, Department of Civil Engineering, entitled NATURAL SOIL PROPERTIES AND
THEIR IMPACT ON ASPHALT ROAD PERFORMANCE CASE STUDY
OF AL-QURNA- CHIBAYISH ROAD

The road system is an important part of any country's social and economic
growth since, it is vital that towns, areas, and neighborhoods should properly
linked. In countries like Iraq, where other types of transportation, like planes,
trains, and rivers, are not well developed, roads are the main way that people and
goods get from one place to another. So, keeping the roads in good state is
important to make sure that traffic is safe, economical and helps the growth of
regional links.
Using the Pavement Condition Index (PCI), as defined by ASTM D6433,
this study aims to assess the pavement condition of Qurna-Chibayish road in
Basra Governorate, Iraq, and to examine the relationship between (PCI) and
natural subgrade soil properties. The research includes visual (PCI) surveys as
well as laboratory tests to evaluate subgrade soil characteristics, including grain
size distribution, specific gravity, Atterberg limits, compaction, and California
bearing ratio.
The classification results of subgrade soil samples taken from (21) road
sections reveal fine grained silty and / or clayey deposits with varied sand
contents, according to the unified system, with AASHTO classes from (A-4) to
(A-7).
The soaked values of California Bearing Ratios (CBR) divided the soil
sections into three, nearly equal groups: poor (CBR ≤ 5%); moderate (5 < CBR ≤
10) and good strength (CBR > 10) conditions.
The road evaluation process generally indicated satisfactory to good
pavement conditions across most of the study area, where (53%) of the (PCI)-
values fall within the range of (70 to 85) and (35%) within (85 to 100). Only
(12%) received a fair rating with (PCI) lie between (55) and (70).
ivIt is evident from this study that, the Californian bearing ratio of the
subgrade has a negligible effect on the pavement performance, as it is evaluated
utilizing the pavement condition index. This is attributed to the addition of a fill
layer that functions as a capping layer where the subgrade is greatly improved.
Therefore, well designed and constructed pavement section would reduce the
adverse effects of week subgrade soil and enhance high (PCI)-values.