1081
Experimental Study on Effect of Initial Moisture Content on Compressive Property of
Compacted Loess Like Silt
Étude expérimentale des caractéristiques de compression des lœss compactés
Bai X.
，
Yang J.
，
Ma F.
College of Architecture and Civil Engineering, Taiyuan University of Technology, Taiyuan Shanxi 030024 China
Yang J.
Department of Civil Engineering Taiyuan Electric Engineering College
，
Taiyuan Shanxi 030013 China
ABSTRACT: Compacted soil, which widely exists in many sorts of engineering projects, is commonly unsaturated soil; and its
physico-mechanical characteristics are great influenced by soil moisture content. To investigate the effect of intial moisture content of
the soil on its compressive property, the numbers of oedometer tests are conducted to the specimens with various initial moisture
contents and compacted under various compacting energies. The test results show that for the compacted loess like silt, when the
compacting energy is same, the compressive modulus decreases with the increased initial moisture content of the specimen, but at the
same initial moisture content
，
the compressive modulus is not monotone increased with the compacting energy increasing, the
maximum compression modulus is reached under a particular compaction energy when the water content is exactly the optimum
water content corresponding to the compaction energy. Therefore the initial moisture content of compacted loess like silt is one of the
most important control indexes for the compaction quality control. To get a high quality of loess like backfill, the initial moisture
content of the backfill must be strict controlled when the dry density meets the design requirement.
RÉSUMÉ : Les caractéristiques physico-mécaniques des lœss compactés ont un effet direct sur la qualité du compactage de ceux-ci.
Elles sont aussi des éléments importants à prendre en compte quand on utilise des lœss pour réaliser des fondations et des couches de
forme. Des essais en laboratoire ont été effectués pour déterminer la loi de variation des caractéristiques de compactage des lœss en
fonction des teneurs en eau et d’énergies de compactage différentes. Les résultats des essais montrent que le module de
compressibilité est plus grand quand la teneur en eau augmente. Pour la teneur en eau optimale correspondant à une énergie donnée de
compactage, le module de compressibilité est alors le plus petit. Par ailleurs, la résistance au cisaillement baisse avec l’augmentation
de la teneur en eau. De même, cette dernière change en fonction de l’énergie de compactage et elle est aussi étroitement liée à la
teneur en eau optimale correspondant à une énergie donnée. Par conséquent, un contrôle strict de la teneur en eau est très important
pour améliorer la qualité de compactage des fondations et des couches de forme réalisées des lœss. Par ailleurs, il faut faire attention à
l’influence de l’énergie utilisée quand on retient le taux de compactage comme critère pour contrôler la qualité de compactage des
lœss, et ceci afin de justifier l’application de ce taux.
KEYWORDS: loess like silt, compaction energy, moisture content, compression modulus.
1 INTRODUCTION
Filling technique is widely used in backfill foundation projects
of buildings, railways, highways and other subgrades. Usually,
backfill refers to the accumulated soil by human activities. The
backfill which is compacted in layers is called as compacted
backfill. It must be compacted under the certain standard of the
material composition, density, water content. The compaction
quality of compacted backfill is directly related to the strength
and stability of backfill foundation and subgrade (Wang, 2004).
With the development of industrialization, the decreasing
availability of proper construction sites has led to the increased
use of mountain area, where the compacted backfill may be
used. Loess like silt is the one of widely used backfill materials.
China has an extensive deposit of loess, which is mainly
found in northwestern China. In this region, loess has been
widely used as backfill material. The study of machenical and
physical properties of natural loess has been reported by many
scholars (Assallay et.al. 1997, Guo et.al. 2000, Xie 2001).
However, the study of machenical and physical properties of
compacted loess is still in its begining stage, the relative reports
are rarel. Therefore, it is necessary to study the mechanical
property of compacted loess like silt.This paper reports the
experimental results about the compressive property of loess
like silt compacted, which may be referred in design and
construction for loess like silt compacting.
2 EXPERIMENT
2.1.
Material
Table.1 Basic properties of tested soil
Particle size distribution (%) Special density
2.7
0.25~0.075 mm
1.3
Plastic limit (%) 16.1
0.075~0.005mm 82.2
Liquid limit (%) 26.0
<0.005 mm
16.5
Plastic index
9.9
The soil used in this program is taken from a loess site in
Luliang city, Shanxi province, China. The basic properties of
the soil are listed in Table 1. According to the Chinese Code,
GB/T50 123-1999
，
Standard for soil test method, it is defined
as silt soil.
2.2.
Test procedure
The test program are divided into 3 steps as follow:
Step 1, determination of the maxium dry density and optimum
moisture content under given compacting energy.
The three groups of remolded loess like silt specimens were
compacted under compacting energies of 2684.9kJ/m
3
, 1208.2
kJ/m
3
and 592.2 kJ/m
3
, respectively. For each group, there were
5 speciemans made at various initial moisture contents to get a
completely moisture vs. density curve, in turn, the maximum
