MINISTRY OF EDUCATION AND TRAINING
UNIVERSITY OF TRANSPORT AND COMMUNICATIONS
NGUYEN THAI LINH
RESEARCH ON THE WORKING OF SOIL CEMENT
COLUMNS IN COMBINATION WITH HIGH STRENGTH
GEOGRID WHEN DEALING WITH SOFT GROUND
IN TRAFFIC CONSTRUCTION
Field of study: Transport Construction Engineering
Code : 9580205
SUMMARY OF DOCTORAL THESIS
HANOI – 2021
This research is completed at:
University of Transport and Communications
Supervisors:
1. AssocProf.Dr. Nguyen Duc Manh
University of Transport and Communications
2. AssocProf.Dr. Pham Hoang Kien
University of Transport and Communications
Reviewer 1: AssocProf.Dr. Nguyen Huy Phuong
Reviewer 2: AssocProf.Dr. Vuong Van Thanh
Reviewer 3: AssocProf.Dr. Hoang Quoc Long
The thesis will be defended before Doctoral-Level Evaluation
Council at University of Transport and Communications
at ......... on ....... in 2021
The thesis can be read at:
1. National Library of Vietnam
2. Library of University of Transport and Communications
AUTHOR’S PUBLICATION LIST
1. Nguyen Thai Linh, Nguyen Duc Manh, Nguyen Hai Ha (2019), "Paralink
technology − method of soft soil stabilization by the soil cement pile with
high tensile geosynthetics", Proceedings of the IVth All-Russian symposium
with participation of foreign scientists, dedicated to the 90th anniversary of
Academician Nikolay Logatchev Irkutsk, pp. 120 - 123. (ISBN 978-5-
9908560-7-3)
2. Nguyen Thai Linh, Nguyen Duc Manh (2020), "Selection of reasonable
experimental models for study behavior of system soil-cement columns with
high-strength geogrid in laboratory", Geotechnical Journal, 1, pp. 65 - 73.
(ISSN - 0868 - 279X)
3. Nguyen Thai Linh, Nguyen Duc Manh, Pham Hoang Kien (2020),
"Experimental study on the settlement of soil cement column combined high
strength geogrid", Transport and Communication Science Journal, 71(2), pp.
102 - 112. (ISSN 1859-2724)
4. Nguyen Thai Linh, Nguyen Duc Manh, Nguyen Hai Ha (2021), "Analysis
of impacting factors for soil-cement column combined high strength
geogrid", Transport and Communication Science Journal, 72(1), pp. 9-15.
(ISSN 2615-9554)
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INTRODUCTION
I. Research background
Over the years, many soft soil treatment solutions have been introduced that not
only solve economic - technical problems, but also aim to optimize the
construction time and environmental protection. The use of soil cement columns
combined with geogrid or high strength geogrid, also known as GRPS (Geogrid
Reinforced Pile Supported) (GRPS) system is also proposed and increasingly
used widely. High strength geogrid when spread on the top of the column forms
a soft transmission layer, increases the load transmitted to the column, reduces
a part of the pressure transmitted to the soft ground between the columns,
thereby reducing the deflection settlement between the column and the
surrounding land. Advantages of the application of GRPS to treat soft ground
under embankments not just for fast construction speed, also for good stability
and reasonable cost, and environmental friendliness.
In addition to the application of the GRPS system popular in the world since the
70s, the studies related to them were also getting lots of attention. These studies
are often updated about working independently or concurrently between
reinforced concrete (reinforced concrete) pile and geogrid, mainly including
load transmission mechanism; the distribution of traction on the mesh; surround
effect; membrane effects... Some countries are also standardized such as BS
8006 (UK), EBGEO 2004 (Germany), FHWA-HRT-13-046 (USA)...
In Vietnam, the solution of soil cement columns combined with geogrid (or
geotextile) has also been applied in the project of Bach Dang bridge (Hai
Phong), thermal power station Duyen Hai (Tra Vinh), internal road of gas plant
Ca Mau (Ca Mau), the road leading to bridge Tran Thi Ly (Da Nang), Metro
Mega Mall Can Tho (Can Tho)… However, studies on the GRPS system are
still very modest, mainly just synthesizing the theory, analyzing the model with
some available geotechnical engineering software, or experimenting on
reinforced concrete piles when having geotextile.
Although there are many studies in the world and in the country, so far the
calculation of the GRPS system often ignores the ground reaction between the
columns as well as does not consider the deformation of the column and the
geogrid when working. This means considering the load transferred to the
column and the geogrid force higher than reality, then the ground between the
column is almost not loaded, which can cause waste in actual production.
Start from the above-mentioned evaluation and analysis, the topic "Research on
the working of soil cement columns in combination with high strength geogrid
when dealing with soft ground in traffic construction" is approached by research
experimental studies on physical models combined with software models
considering interaction factors in the column foundation system such as ground
pressure (σ's), column deformation (Scol), or mesh deformation (Sgrid) is urgent,
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has scientific significance and practical value.
II. Research objective
From the experimental studies on the indoor model, the analysis of the software
model under the load of the column system combined with the high strength
geogrid considering the ground pressure, the column deformation, and the mesh
deformation, propose new calculation formulas, which are more suitable in
GRPS design.
III. Reseach contents
The content of the thesis focuses on the following issues:
1. General study on the solutions of soil cement columns combined with
geogrid to treat soft ground for construction.
2. Three-dimensional software analysis to determine the factors affecting the
working of the mangrove column system combined with the high strength
geogrid.
3. Construction and research on the experimental model of soil cement
columns combined with high strength geogrid indoor with the scaling ratio
1/25.
4. Constructing and proposing the calculation formulas of GRPS system
based on standard theoretical foundation BS 8006, when considering the
ground reaction and deformation of the column problem in the soil cement
columns combined with high strength geogrid.
IV. Scientific and practical contribution
- Scientific contribution
On the basis of the theoretical synthesis, software model analysis identifies a
few limitations of the calculation methods of soil cement columns combined
with geogrid that are commonly applied today.
From the physical model and the software model used to research the soil
cement columns combined with the high strength geogrid, propose a more
complete calculation formula, not only as premise and methodological basis but
also as the radical reliable scientific basis for other similar research in Vietnam
in the coming time.
- Practical contribution
Considering the factors related to transmission efficiency, tensile force in the
soil cement columns combined with geogrid when working, and taking them
into consideration in the proposed formulas still ensures reliability on load
bearing, more realistic reflection, helping to reduce costs when applying this
solution in construction practice.
Research results are good professional documents to serve teaching and training
at related units in Vietnam.
