1. 1-1 Significance 2-1 Properties of Permeable Piles
2-2 Properties of Pervious Concrete
4-2 Large-Scale Testing – Soil Properties4-1 Pervious Concrete Material Properties3-1 Soil Boxes and Reaction System
3-2 Major Sensors and Capabilities
4-3 Development of Pile Installation Technique 4-4 Pile Dimensions and Instrumentation
4-5 Results
4-5 Results - Continued
4-6 Summary and Conclusions
4-7 Acknowledgment
Pervious Concrete Piles: An Innovative Ground Improvement Alternative
GRANT No. 0927743 – Geotechnical Engineering Program
1- Introduction
3- Research Facility
4- Recent Research Activities - Continued
– Permeable granular piles (i.e., sand compaction piles, stone columns
and rammed aggregate piers) are commonly used to support
structures and highway facilities constructed on soft or loose soils.
– Although the use of permeable granular piles increases the time rate
of consolidation, reduces liquefaction potential, improves bearing
capacity and stability, and reduces settlement of poor soils, these
piles have low stiffness and strength that depend on the properties of
surrounding soil. Therefore, granular piles have limited use in very
soft clays and silts, and in organic and peat soils.
– The goal of the research team is to develop an innovative ground
improvement method that uses pervious concrete piles.
– When compared to the properties of granular piles, pervious concrete
material provides more than ten times the strength, an increase of two
orders of magnitude in modulus, and comparable permeability. The
higher elastic modulus and strength of pervious concrete improves
load transfer and load-carrying capacity of piles and potentially
provides a cost-effective alternative.
Muhannad T. Suleiman (PI, Lehigh University), Anne Raich (Co-PI), and Matthew O’Loughlin (Lafayette College)
1-2 Vision, Goal and Objectives
- The long-term goal of the research team is to develop an innovative
ground improvement technique using pervious concrete piles to improve
load transfer, global and local stability, reduce settlement, increase time
rate of consolidation, and reduce liquefaction potential of structures,
embankments, and transportation facilities constructed on poor
foundation soils.
- This project represents the first step of achieving this goal by conducting
a laboratory experimental program, simulating the behavior of test units,
and formulating analytical methodologies.
Main objectives:
1. Develop pervious concrete mixtures having properties appropriate for
ground improvement applications;
2. Evaluate the effects of construction techniques on soil and pervious
concrete pile properties and on soil-pile interaction;
3. Develop and validate analysis methods that model the effects of
construction procedures on soil and pervious concrete pile properties,
soil-pile interaction, and the behavior of pervious concrete piles
subjected to different loads;
4. Generate the seed data for future full-scale field tests; and
5. Educate students, researchers, professionals, and K-12 students and
teachers on the properties of pervious concrete materials, pervious
concrete piles and the recommended construction procedures.
- Sheet and Free Form Pressure Sensors
- Shape Acceleration Arrays (SAA)
- Push-in Pressure Cells
- Earth Pressure Cells
- Soil Storage and Moving System
- Nuclear Density Gauge
- Multi-party Video Conferencing
- Analytical Software: e.g. ABAQUS, LPILE
4- Recent Research Activities
3-D Schematic of the Soil Boxes and Reaction Frame
Deformed shape measured
using SAA
Video conferencing
Steel angle with rollers to
slide top box relative to
lower box
Upper soil box
Lower soil box
Drainage base
Drainage pipe
Reaction frame
- Several natural and crushed aggregate materials were used to
prepare pervious concrete samples.
- The compressive strength, tensile strength, unit weight, porosity
and permeability of the pervious concrete samples were measured.
- The 7-day compressive strength of pervious concrete samples
ranged from 13 MPa to 26 MPa, the porosity ranged from 15% to
23%, the coefficient of permeability ranged from 1.1 to 2.2 cm/sec.,
and the unit weight ranged from 17.1 to 19.5 kN/m3.
- Based on the 7-day compressive strength of pervious concrete
made using different aggregate types, pervious concrete made with
commercially available pea gravel was selected for the test pile.
- The pea gravel was sieved and the material passing the 9.5 mm
sieve and retained on sieve No. 4 was used.
- The pervious concrete mixture used in preparing the pervious pile
has the following properties; unit weight of 18.03 kN/m3, porosity of
15.4%, 7-day compressive strength of 17.2 MPa, and permeability
of 1.2 cm/sec.
Installation of pervious concrete pile
showing the bracing system
- The installation technique resulted in a continuous pile and that the
pile failure was a punching shear failure (no bulging into the
surrounding loose sand).
- Although it was harder to expose the aggregate pile, the pile most
probably failed in bulging into the surrounding soil.
- The pervious concrete of the pile has the following properties: unit
weight of 17.2 kN/m3, porosity of 7% and permeability of 0.38 cm/sec.
LAFAYETTE
C O L L E G E
2- Literature Review
Granular Pile
Friction Angle
(degrees)
Elastic
Modulus
(MPa)
Stress
Concentration
Ratio
Permeability
(cm/sec.)
References
Sand
Compaction
Pile
30–36 25–40 1.5–6.0 0.05–0.65
Bergado et al.,
1988; Aboshi et
al., 1979; and
Bergado et al.,
1994;
Stone Column 35–45 30–70 2.0–8.5 0.08–2.0
Mitchell, 1981;
Barksdale and
Bachus, 1983;
and Baez, 1995
Rammed
Aggregate
Pier
48–52 60–120 2.0–10
NM (Not
Measured)
Hoevelkamp,
2001; and
White and
Suleiman, 2004
Porosity
0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45
7dayCompressiveStrength(MPa)
0
5
10
15
20
25
30
CoeffecientofPermeability(cm/sec.)
0.00
0.25
0.50
0.75
1.00
1.25
1.50
1.75
2.00
7-day strength (MPa) = 32.2 - 66.7 * (porosity)
Permeability = 0.0184 * Exp
(13.08 * porosity)
Moisture Content (%)
0 2 4 6 8 10
DryUnitWeight(kN/m3
)
10
12
14
16
18
20
22
24
Maximum density
Minimum density
Particle Size (mm)
0.01 0.1 1 10
%Passing
0
10
20
30
40
50
60
70
80
90
100
- The soil was classified as well-graded sand.
- The soil was placed in the large box by raining the soil from a
height of approximately 1.5 m.
- The average dry unit weight of the soil was 16.1 kN/m3 and the
average moisture content was 2.0%.
Particle size distribution of sand
Relative density test results
Raining the soil into the box
Measurement of soil density
and moisture content
- The research team developed an installation technique in the
laboratory that simulates a field technique used to install granular
piles.
- The developed installation system consists of a hollow steel pipe
with a specially designed cone at the tip.
- The pipe with the attached cone is vibrated into the soil using a
concrete vibrator attached to the pipe.
- A bracing system was also designed to ensure the verticality of the
installed pile.
- During pipe advancement, the tip of the cone stay closed. Once
reaching the desired depth, the pipe is lifted upward where the tip of
the cone start to open.
- The pervious concrete is placed from the top of the pipe to fill the
space created by the driven pipe.
- During concrete installation, the pipe is vibrated to compact the
installed pervious concrete pile.
- Using this installation technique, one pervious concrete pile and
one aggregate pile made with the same aggregate used in the
pervious concrete were installed and tested under vertical load.
Hollowsteel pipe
Concretevibrator
Open cone tip during installation
Cone tip during pile installation
- The inside diameter of the installed pile was 76 mm and the length
of the pile was 86.4 cm.
- Instrumentation to measure the vertical displacement and the
applied vertical load were used to measure the response of both the
pervious concrete pile and the aggregate pile.
Vertical load test setup
- The ultimate capacity of the pervious concrete pile was 9.8 kN and
the stiffness of the load-displacement curve was 3123 N/mm.
- For the aggregate pile that was installed using the same technique,
the ultimate capacity was 2.2 kN and the stiffness of the load-
displacement curve was 716 N/mm.
- The ratio of the ultimate capacity of the pervious concrete pile to the
ultimate capacity of the aggregate pile was 4.4 time. When
comparing the stiffness at similar vertical displacement, the ratio of
the stiffness of the pervious pile to that of the aggregate pile was
4.3 time.
Vertical displacement (mm)
0 20 40 60 80 100 120
Verticalload(N)
0
2000
4000
6000
8000
10000
12000
Pervious concrete pile
Aggregate pile
9786 N
2225 N
Measured response of pervious
concrete pile and aggregate pile
Exposed pervious pile
- This paper describes the vision, objectives and recent research
activities of this project to develop a new ground improvement
alternative using pervious concrete piles.
- The paper presents preliminary results of vertical load tests on
pervious concrete piles and aggregate piles.
- The preliminary results show that the ratio of the ultimate capacity of
the pervious concrete pile was 4.4 times that of the ultimate capacity
of the aggregate pile. When comparing the stiffness at similar vertical
displacement, the ratio of the stiffness of the pervious pile to that of
the aggregate pile was 4.3 time.
- The authors would like to acknowledge the support of the
Geotechnical Engineering Program of the Civil, Mechanical, and
Manufacturing Innovation (CMMI) Division at National Science
Foundation (Grant No. 0927743).
- The authors would like to acknowledge the help of the following
undergraduate students: Matthew Keehn and Kristi Kostallari.