Ground improvement techniques

GC. UNIVERSITY FAISALABAD
LAYYAH CAMPUS
BS CIVIL DEPARTMENT
SUBJECT; Soil Mechanics and Ground
improvement Techniques.
Prepaired BY; Qasim munawar virk 12-CET-34
CLASS; BS CIVIL (B)
Bs civil Engineering and Technology
GC.UNIVERSITY FAISALABAD
LAYYAH CAMPUS
Engr.Qasim munawar virk www.qasimvirk29@yahoo.com

GROUND IMPROVEMENT
1. Dry Soil Mixing
2. Dynamic Compaction
3. Injection Systems
4. Rapid Impact Compaction
5. Rigid Inclusions
6. Vibro Compaction
7. Vibro Concrete Columns
8. Vibro Piers®
9. Vibro Replacement
10. Wet Soil Mixing
Dry Soil Mixing
Dry soil mixing is a ground improvement technique that improves the characteristics of soft,
high moisture content clays, peats, and other weak soils, by mechanically mixing them with
dry cementitious binder to create soilcrete. To construct columns, a high speed drill advances
drill steel with radial mixing paddles located near the bottom of the drill string. During
penetration, the tool shears the soils preparing them for mixing. After the tool reaches the
design depth, the binder is pumped pneumatically through the drill steel to the tool where it is
mixed with the soil as the tool is withdrawn. To perform mass soil mixing, or mass
stabilization, a horizontal axis rotary mixing tool is located at the end of a track hoe arm. The
binder is pneumatically injected to the soil mixing tool through a feed pipe which is attached to
the track hoe arm.
The dry soil mixing process constructs individual soilcrete columns, rows of overlapping
columns or 100% mass stabilization, all with a designed strength and stiffness. The technique
has been used to increase bearing capacity, mitigate liquefaction, fixate contaminants in situ,

decrease settlement and increase global stability for planned structures, embankments and
levees. Dry soil mixing is low vibration, quiet, and clean, and uses readily available materials.
The process is often used in high ground water conditions and has the advantage of
producing practically no spoil for disposal.
Dry soil mixing is best suited for soils with moisture contents greater than 60 percent and near
the liquid limit. Soft cohesive soils, including organics, are usually targeted as other soil types
can often be treated more economically with other techniques. Soils vary widely in their ability
to be mixed, depending on the soil type, strength, water content, plasticity, stratigraphy, and
texture. Organic soil and peats can often be stabilized, but laboratory testing is always
recommended prior to design. With dry soil mixing, treatment is possible to depths up to 60
feet. Obstructions are sometimes predrilled ahead of the soil mixing process.
Dynamic Compaction
Dynamic compaction is a ground improvement technique that densifies soils and fills by using
a drop weight. The drop weight, typically hardened steel plates, is lifted by a crane and
repeatedly dropped on the ground surface. The drop locations are typically located on a grid
pattern, the spacing of which is determined by the subsurface conditions and foundation
loading and geometry. Treated granular soils and fills have increased density, friction angle
and stiffness. The technique has been used to increase bearing capacity, and decrease
settlement and liquefaction potential for planned structures. In shallow karst geologies, it has
been used to collapse voids prior to construction, thereby reducing sinkhole potential.
Dynamic compaction has also been used to compact landfills prior to construction of a
parking lots, roadways, and embankments.
Injection Systems
Injection stabilization is the pressure injection of aqueous solutions into the ground. The
composition of the aqueous solution depends on the application, which commonly includes
stabilization of expansive soils and railroad subgrades. Purpose-built injection units advance
injection pipes into the treatment zone. An aqueous solution of water, lime slurry, or potassium
chloride is injected to reduce shrink/swell potential for treatment of expansive soils. The
technique has been used to treat below planned and existing railways, roadways and

buildings.
Rapid Impact Compaction
Rapid Impact Compaction (RIC) is a ground improvement technique that densifies shallow,
loose granular soils, using a hydraulic hammer which repeatedly strikes an impact plate. The
energy is transferred to the underlying loose granular soils and rearranges the particles into a
denser configuration. The impact locations are typically located on a grid pattern, the spacing
of which is determined by the subsurface conditions and foundation loading and geometry.
Treated granular soils and fills have increased density, friction angle and stiffness. The
technique has been used to increase bearing capacity, and decrease settlement for planned
structures.
Rigid Inclusions (Controlled Stiffness Columns)
Rigid inclusions is a ground improvement technique that transfers loads through weak strata
to a firm underlying stratum using high modulus, controlled stiffness columns. A bottom-feed
mandrel with a top-mounted vibrator is advanced through the weak strata to the underlying
firm stratum. Granular bearing soils are densified by displacement. Concrete is then pumped
through the mandrel, which opens as it is raised. The mandrel may be raised and lowered
several times within the bearing depth to construct an expanded base if required by the

design. The mandrel is then extracted while a positive concrete head is maintained. The
concrete fills the void created by the mandrel during extraction, and terminates in an upper
strong stratum or is subsequently overlain by an engineered relieving platform. The improved
performance results from the reinforcement of the compressible strata with the high modulus
columns. The technique has been used to increase allowable bearing pressure and decrease
settlement for planned structures, embankments and tanks.
Vibro Compaction
Vibro compaction is a ground improvement technique that densifies clean, cohesionless
granular soils by means of a downhole vibrator.
The vibrator is typically suspended from a crane and lowered vertically into the soil under its
own weight. Penetration is usually aided by water jets integrated into the vibrator assembly.
After reaching the bottom of the treatment zone, the soils are densified in lifts as the probe is
extracted. During vibro compaction, clean sand backfill is typically added at the ground
surface to compensate for the reduction in soil volume resulting from the densification
process. The vibratory energy reduces the inter-granular forces between the soil particles,
allowing them to move into a denser configuration, typically achieving a relative density of 70
to 85 percent. The treated soils have increased density, friction angle and stiffness.
Compaction is achieved above and below the water table.
The improved soil characteristics depend on the soil type and gradation, spacing of the
penetration points and the time spent performing the compaction. Generally, the vibro
compaction penetration spacing is between 6 feet and 14 feet, with centers arranged on a
triangular or square pattern. Compaction takes place without setting up internal stresses in
the soil, thus ensuring permanent densification.

The use of clean sand backfill during vibro compaction allows the original site elevation to be
maintained. However, on sites where the planned final grade is below the existing grade,
lowering of the site elevation may be desirable. In these instances, the ground surface is
allowed to subside during the compaction effort.
Vibro compaction permits the use of economical spread footings with design bearing
pressures generally of 5 ksf up to 10 ksf. Settlement and seismic liquefaction potentials are
reduced. The required treatment depth is typically in the range of 15 to 50 feet, but vibro
compaction has been performed to depths as great as 120 feet. Examples of previously
performed applications include increasing bearing capacity, decreasing settlement and
mitigating liquefaction for planned structures, embankments, railways and roadways.
Vibro Concrete Columns
Vibro concrete columns is a ground improvement technique that transfers loads through weak
strata to a firm underlying stratum, using high modulus concrete columns. A bottom-feed
down-hole vibratory probe is advanced through the weak strata to the underlying firm stratum.
Granular bearing soils are densified by the vibrator. Concrete is then pumped through the
bottom feed tremie tube. The vibrator is raised and lowered several times within the bearing
depth to construct an expanded base. The vibrator is then raised to the surface as concrete
fills the void created by the vibrator during extraction. Typically, the vibrator also repenetrates
the top of the column to construct an enlarged head which is subsequently overlain by a
geogrid reinforced soil relieving platform. The technique has been used to increase allowable
bearing pressure and decrease settlement for planned structures, embankments and tanks,
and increase global stability for embankments.

Vibro Piers® (Aggregate Piers)
Vibro Piers is a ground improvement technique that constructs short, stiff aggregate piers to
reinforce fine grained soils. The pier location is initially predrilled for soils in which the hole will
remain open. In soils that cave or collapse, a bottom feed vibrator can be employed. The
downhole vibrator is lowered vertically to the designed tip of the pier typically with a standard
crane. Aggregate (new crushed stone or recycled concrete) is then introduced into the hole
and is compacted in lifts by repeated penetrations with the vibrator. The vibratory energy from
the vibrator densifies the aggregate and any surrounding granular soil. The high modulus pier
reinforces the treatment zone. The technique has been used to increase bearing capacity and
decrease settlement for planned structures, embankments, tanks and towers.
Vibro Replacement (Stone Columns)
Vibro replacement is a ground improvement technique that constructs dense aggregate
columns (stone columns) by means of a crane-suspended downhole vibrator, to reinforce all
soils and densify granular soils. Vibro replacement stone columns are constructed with either
the wet top feed process, or the dry bottom feed process.
In the wet top feed process, the vibrator penetrates to the design depth by means of the

vibrator’s weight and vibrations, as well as water jets located in the vibrator’s tip. The stone
(crushed stone or recycled concrete) is then introduced at the ground surface to the annular
space around the vibrator created by the jetting water. The stone falls through the annular
space to the vibrator tip, and fills the void created as the vibrator is lifted several feet. The
vibrator is lowered, densifying and displacing the underlying stone. The vibro replacement
process is repeated until a dense stone column is constructed to the ground surface.
The dry bottom feed process is similar except that no water jets are used and the stone is fed
to the vibrator tip through a feed pipe attached to the vibrator. Predrilling of dense strata at the
column location may be required for the vibrator to penetrate to the design depth. Both
methods of construction create a high modulus stone column that reinforces the treatment
zone and densifies surrounding granular soils.
Wet Soil Mixing
Wet soil mixing, also known as the Deep Mixing Method, is a ground improvement technique
that improves the characteristics of weak soils by mechanically mixing them with cementitious
binder slurry. To construct columns, a powerful drill advances drill steel with radial mixing
paddles located near the bottom of the drill string. The binder slurry is pumped through the
drill steel to the tool as it advances and additional soil mixing is achieved as the tool is
withdrawn. To perform mass wet soil mixing, or mass stabilization, a horizontal axis rotary
mixing tool is located at the end of a track hoe arm.
The binder slurry is injected through a feed pipe attached to the arm. The process constructs
individual soilcrete columns, rows of overlapping columns or 100% mass stabilization, all with
a designed strength and stiffness. The technique has been used to increase bearing capacity,
decrease settlement, increase global stability, and mitigate liquefaction potential for planned
structures, tanks, embankments and levees. Wet soil mixing has also been used to construct
in situ gravity retaining structures, and to facilitate tunnel construction or remediate the impact
tunneling may have on nearby structures. Soil stabilization by wet soil mixing can provide
structural support and/or it can greatly reduce lateral loads on bulkhead walls.
Wet soil mixing is best suited for soils with moisture contents up to 60 percent. Soft cohesive
soils are usually targeted as other soil types can often be treated more economically with
other techniques. If the moisture content is greater than 60 percent, dry soil mixing may be
more economical. Soils vary widely in their ability to be mixed, depending on the soil type,

strength, water content, plasticity, stratigraphy, and texture. Almost any soil type, including
organics, can be treated with wet soil mixing although some soils may require significant
binder and/or pretreatment. With wet soil mixing, treatment is possible to depths up to 100
feet. Depending on the soil type, excess soilcrete generated may range from 10 to 40 percent
of the treated volume. Stiff soils and obstructions are sometimes predrilled ahead of the soil
mixing process.
Mixing shaft speed, penetration rate, batching, and pumping operations are typically adjusted
after constructing one or more test columns in a convenient area on site.
GROUTING
1. Cement Grouting
2. Chemical Grouting
3. Compaction Grouting
4. Fracture Grouting
5. Jet Grouting
6. Polyurethane Grouting
Cement Grouting (High Mobility Grouting)
Cement grouting, also known as slurry grouting or high mobility grouting, is a grouting
technique that fills pores in granular soil or voids in rock or soil, with flowable particulate
grouts. Depending on the application, Portland cement or microfine cement grout is injected
under pressure at strategic locations either through single port or multiple port pipes. The
grout particle size and soil/rock void size must be properly matched to permit the cement

grout to enter the pores or voids. The grouted mass has an increased strength and stiffness,
and reduced permeability. The technique has been used to reduce water flow through rock
formations beneath dams and to cement granular soils to underpin foundations or provide
excavation support.
For underpinning applications, cement grouting may offer an economic advantage over
conventional approaches such as removal and replacement, or piling, and can be
accomplished where access is difficult and space is limited. Since the effectiveness of cement
grouting is independent of structural connections, the technique is readily adaptable to
existing foundations. Usually, cement grouting can be accomplished without disrupting
normal facility operations.
Chemical Grouting
Chemical grouting is a grouting technique that transforms granular soils into sandstone-like
masses, by permeation with a low viscosity grout. The soils best suited for this technique are
sands with low fines content. Typically, a sleeve port pipe is first grouted into a predrilled hole.
The grout is injected under pressure through the ports located along the length of the pipe.
The grout permeates the soil and solidifies it into a sandstone-like mass. The grouted soil has
increased strength and stiffness, and reduced permeability. Chemical grouting has been used
to underpin existing foundations, create excavation support walls, create water cutoff walls
and stabilize soils for tunneling.

For underpinning applications, chemical grouting offers the advantages of being easily
performed where access and space is limited, and of not requiring a structural connection to
the foundation being underpinned. A common application of chemical grouting is to provide
both excavation support and underpinning when an excavation is planned immediately
adjacent to an existing structure. Usually, chemical grouting can be accomplished without
disrupting normal facility operations.
Chemical grouting equipment is well-suited for tunneling applications in urban environments,
whether for stabilizing soil around break-ins or break-outs, or for mitigating settlement of
overlying structures within the influence of the tunnel alignment.
Compaction Grouting (Low Mobility Grouting)
Compaction grouting, also known as Low Mobility Grouting, is a grouting technique that
displaces and densifies loose granular soils, reinforces fine grained soils and stabilizes
subsurface voids or sinkholes, by the staged injection of low-slump, low mobility aggregate
grout. Typically, an injection pipe is first advanced to the maximum treatment depth. The low
mobility grout is then injected as the pipe is slowly extracted in lifts, creating a column of
overlapping grout bulbs. The expansion of the low mobility grout bulbs displaces surrounding
soils. When performed in granular soil, compaction grouting increases the surrounding soils
density, friction angle and stiffness. In all soils, the high modulus grout column reinforces the
soils within the treatment zone. By sequencing the compaction grouting work from primary to
secondary to tertiary locations, the densification process can be performed to achieve
significant improvement. Compaction grouting has been used to increase bearing capacity,
and decrease settlement and liquefaction potential for planned and existing structures. In
karst geologies, compaction grouting has been used to treat existing sinkholes or to reduce
the sinkhole potential in sinkhole prone areas.

Compaction grouting was developed in the 1950s as a remedial measure for the correction of
building settlement, and used almost exclusively for that purpose for many years. Over the
past 25 years, however, compaction grouting technology has evolved to treat a wide range of
subsurface conditions for new and remedial construction. These include rubble fills, poorly
placed fills, loosened or collapsible soils, sinkhole sites, and liquefiable soils.
Compaction grouting offers an economic advantage over conventional approaches such as
removal and replacement, or piling, and can be accomplished where access is difficult and
space is limited. Compaction grouting for treatment beneath existing structures is often
selected because the low mobility grout columns do not require structural connection to the
foundations.
Fracture Grouting
Fracture grouting, also known as compensation grouting, is a grouting technique that
hydrofractures in situ soil, using neat fluid grout. A sleeve port pipe is grouted into a predrilled
hole beneath a foundation. The grout is injected under pressure at strategic locations through
the ports in the pipe. Once the hydrofracture pressure of the soil is exceeded, fractures open
up in the soil and are immediately expanded by the subsequent influx of grout. The process
results in controlled heave of the overlying soils and structures. The technique has been used
to relevel structures or to protect structures from settlement while a tunnel machine passes
below.

Jet Grouting
Jet grouting is a grouting technique that creates in situ geometries of soilcrete (grouted soil),
using a grouting monitor attached to the end of a drill stem. The jet grout monitor is advanced
to the maximum treatment depth, at which time high velocity grout jets (and sometimes water
and air) are initiated from ports in the side of the monitor. The jets erode and mix the in situ
soil as the drill stem and jet grout monitor are rotated and raised.
Depending on the application and soils to be treated, one of three variations is used: the
single fluid system (slurry grout jet), the double fluid system (slurry grout jet surrounded by an
air jet) and the triple fluid system (water jet surrounded by an air jet, with a lower grout jet).
The jet grouting process constructs soilcrete panels, full columns or anything in between
(partial columns) with designed strength and permeability. Jet grouting has been used to
underpin existing foundations, construct excavation support walls, and construct slabs to seal
the bottom of planned excavations.

Jet grouting is effective across the widest range of soil types of any grouting system, including
silts and most clays. Because it is an erosion-based system, soil erodibility plays a major role
in predicting geometry, quality and production. Cohesionless soils are typically more erodible
by jet grouting than cohesive soils. Since the geometry and physical properties of the soilcrete
are engineered, the properties of the soilcrete are readily and accurately predictable.
Jet grouting’s ability to construct soilcrete in confined spaces and around subsurface
obstructions such as utilities, provides a unique degree of design flexibility. Indeed, in any
situation requiring control of groundwater or excavation of unstable soil (water-bearing or
otherwise) jet grouting should be considered.
Polyurethane Grouting
Polyurethane grouting is a grouting technique that involves the injection of expanding
polyurethane to cutoff water flow through concrete joints or cracks or to fill voids beneath
slabs or behind subsurface concrete walls or to relevel slabs. The grout is injected under low
pressure through a predrilled hole. The grout then expands to fill the crack or void. Many
polyurethane grout products are available with variations in viscosity, reaction time, reaction
with water, expansion characteristic and flexibility of the reacted grout. Polyurethane grouts
can be single or multi-component grouts and can react when coming in contact with water or
require a reactant. It is important to select the proper grout for the specific application. The
process fills voids either for water cutoff or structural support. The technique has been used to
fill voids beneath slabs, relevel slabs, fill voids behind subsurface walls and seal leaking
cracks and joints in subsurface structures such as manholes or tunnels.

Polyurethane Injection is a releveling technique that raises concrete slabs and fills voids,
using the regulated injection of lightweight, non-hazardous expanding polyurethane grout.
When ground improvement is needed along with releveling, compaction grouting is performed
for ground improvement and then polyurethane grout is injected to fill remaining voids and
complete the lifting to final grade. Deeper loose zones are first densified with compaction
grouting. Holes are then drilled through the concrete slab through which polyurethane foam is
injected while monitoring the slab level from the surface. After re-leveling, the drill holes are
cleaned and filled with cement grout. The treatment results in a densified subgrade, filled
voids and a re-leveled and stabilized concrete slab.
STRUCTURAL SUPPORT
1. Augercast Piles
2. Drilled Shafts
3. Driven Piles
4. Franki Piles (PIFs)
5. Helical Piles
6. Jacked Piers
7. Macropiles®
8. Micropiles
9. Pit Underpinning
Augercast Piles
Augercast piles, also known as continuous flight auger piles (CFA), are deep foundation
elements that are cast-in-place, using a hollow stem auger with continuous flights. The auger
is drilled into the soil and/or rock to design depth. The auger is then slowly extracted,
removing the drilled soil/rock as concrete or grout is pumped through the hollow stem. The
grout pressure and volume must be carefully controlled to construct a continuous pile without
defects. Reinforcing steel is then lowered into the wet concrete or grout. The finished
foundation element resists compressive, uplift and lateral loads. The technique has been

used to support buildings, tanks, towers and bridges.
Drilled Shafts
Drilled shafts, also known as caissons, are typically high-capacity cast-in-place deep
foundation elements constructed using an auger. A hole having the design diameter of
planned shaft is first drilled to the design depth. If the hole requires assistance to remain
open, casing or drilling fluid is used. Full-length reinforcing steel is then lowered into the hole
and the hole is filled with concrete. The finished foundation element resists compressive, uplift
and lateral loads. The technique has been used to support buildings, tanks, towers and
bridges.
Driven Piles
Driven piles are deep foundation elements driven to a design depth or resistance. If
penetration of dense soil is required, predrilling may be required for the pile to penetrate to
the design depth. Types include timber, pre-cast concrete, steel H-piles, and pipe piles. The
finished foundation element resists compressive, uplift and lateral loads. The technique has
been used to support buildings, tanks, towers and bridges. Driven piles can also be used to
provide lateral support for earth retention walls. Steel sheet piles and soldier piles are the
most common type of driven piles for this application.

Franki Piles (PIFs)
Franki Piles, also known as Pressure Injected Footings (PIFS), are high-capacity cast-in-
place deep foundation elements constructed using a drop weight and casing. A 2 to 3 foot
diameter steel casing is vertically positioned at a planned PIF location. The bottom 3 to 5 feet
of the casing is filled with a very dry concrete mix. A steel cylinder with a diameter slightly less
than the casing is then repeatedly dropped inside the casing on the dry mix. The mix locks
into the bottom of the casing and the repeated blows of the drop weight advance the casing to
the design depth. The casing is then restrained from further advancement and additional
weight drops expel the dry mix out of the bottom of the casing. Additional dry mix is added
and driven from the casing until a design resistance to further displacement is achieved.
Reinforcing steel and concrete are then placed in the casing and the casing is extracted. The
finished foundation element resists compressive, uplift and lateral loads. The technique has
been used to support buildings, tanks, towers and bridges.

Helical Piles
Helical piles, also known as helical piers, are deep foundation underpinning elements
constructed using steel shafts with helical flights. The shafts are advanced to bearing depth
by twisting them into the soil while monitoring torque to estimate the pile capacity. A thorough
understanding of the subsurface conditions is necessary to properly interpret the torque
conversion. After reaching design capacity, the tops of the shafts are bracketed to the
structure's footing. The finished piles effectively underpin the footing, stopping settlement
Jacked Piers
Jacked piers are deep foundation underpinning elements constructed using small-diameter
steel pipes. The steel pipes are advanced to bearing depth by hydraulic jacks that are
fastened to the structure being underpinned. Using the structure as the reaction load, the jack
hydraulic pressure required to advance the pile is used to determine the pile capacity. In this
way, each pile is essentially load tested. After reaching bearing depth, the tops of the pipes
are bracketed to the structure’s footing. The finished piers effectively stop settlement and can
raise the structure, closing cracks and correcting other structural flaws caused by the
settlement and/or ground movement.

Macropiles®
A macropile is an ultra-high-capacity micropile, a deep foundation element constructed using
steel pipe. Typically, the pipe is advanced using a drilling technique to the design depth. In
cases where the drill hole remains open without casing, an open hole can be advanced to the
bearing depth and the pipe subsequently installed. Reinforcing steel in the form of all-thread
bar or concentric pipes is inserted into the pipe. High-strength cement grout is then pumped
into the pipe or pipes by tremie. The pipe may terminate above the bond zone with the
reinforcing steel extending full depth. The finished foundation element resists compressive,
uplift and lateral loads. The macropile technique has been used to support buildings and
bridges.
Micropiles (Minipiles)
Micropiles, also known as minipiles, (and less commonly as pin piles, needle piles and root
piles) are deep foundation elements constructed using high-strength, small-diameter steel
casing and/or threaded bar. Capacities vary depending on the micropile size and subsurface
profile. Allowable micropile capacities in excess of 1,000 tons have been achieved.
The micropile casing generally has a diameter in the range of 3 to 10 inches. Typically, the
casing is advanced to the design depth using a drilling technique. Reinforcing steel in the

form of an all-thread bar is typically inserted into the micropile casing. High-strength cement
grout is then pumped into the casing. The casing may extend to the full depth or terminate
above the bond zone with the reinforcing bar extending to the full depth. The finished
micropile (minipile) resists compressive, uplift/tension and lateral loads and is typically load
tested in accordance with ASTM D 1143 (compressive), ASTM D 3689 (uplift/tension), and
ASTM D 3966 (lateral). The technique has been used to support most types of structures.
Hayward Baker’s micropile drill rigs allow installation in restricted access, low headroom
interiors, permitting facility upgrades with minimal disruption to normal operations. (Click on
“view all images” at the left to see typical applications).
Pit Underpinning
Pit underpinning is a traditional underpinning technique that stabilizes structures prior to
adjacent excavation, using concrete and mortar. A limited width pit (panel) is excavated and
shored by hand below the structure and extends to the underpinning design depth. The pit is
then filled with concrete, leaving several inches of space under the bottom of the structure.
Mortar is then packed into the space to provide the load transfer. After the concrete and
mortar achieve sufficient strength, additional adjacent panels can be constructed as
necessary. The finished, cured underpin allows adjacent excavation to take place.

EARTH RETENTION
1. Anchors
2. Anchor Block Slope Stabilization
3. Gabion Systems
4. Micropile Slide Stabilization System (MS³)
5. Sheet Piles
6. Soil Nailing
7. Soldier Piles & Lagging
Anchors
Anchors are stabilization and support elements that transfer tension loads, using high-
strength steel bars or steel strand tendons. A full-length hole is drilled through the soil and into
the bond zone in soil or rock using casing if necessary. Threadbar or strand tendon is inserted
into the hole and the hole is filled with high-strength grout. Any casing used is then extracted.
The length of bar or strand above the bond zone is covered by a bond breaker to eliminate
load transfer above the bond zone. The anchor head is then generally tensioned and
connected to the structure requiring the support.
Anchor Block Slope Stabilization
Anchor block slope stabilization is an earth retention technique that stabilizes slopes or
existing retaining walls, using anchored reaction blocks. The block layout pattern is typically in
rows across the slope or retaining wall requiring stabilization. Initially, anchors are installed at
the planned center of each block location. Reaction blocks are either precast or cast-in-place
around the anchor heads. Bearing plates are then installed and the anchors are tensioned
against the blocks. The finished anchored reaction blocks resist the movement of the retained
soil or wall.

Gabions
Gabions are an earth retention technique in which gravity retaining walls are formed using
rectangular, interconnected, stone-filled wire baskets. The corrosion-resistant baskets are
placed and filled on site by hand. The baskets are stacked on one another and are generally
stepped back to construct a tiered or sloped wall. Gabion walls are effective in protecting
slopes from erosion. The technique has been used to construct temporary or permanent
retaining walls and channel linings.
Micropile Slide Stabilization
System (MS³)
Micropile Slide Stabilization System (MS³) is a slope stability technique which utilizes an array
of micropiles, sometimes in combination with anchors. A reinforced concrete beam is initially
constructed on the ground surface, through which micropiles are then drilled at angles. The
micropiles are then grouted and connected to the beam. The finished micropiles act in tension
and compression to effectively create an integral, stabilized ground reinforcement system to
resist sliding forces in the slope

Secant or Tangent Piles
Secant or tangent piles are columns constructed adjacent (tangent) or overlapping (secant)
each other to form structural walls that resist lateral pressures and groundwater inflow for
bulkhead support, earth retention, groundwater control, or slope stability. The columns are
constructed with soil mixing, jet grouting, augercast, or drilled shaft methods. Sequenced
construction of the individual elements that comprise the finished barrier helps to ensure a
tight seal between elements for complete water cut off. The design can incorporate steel bar
or beams for reinforcement. Anchors provide additional lateral support, if needed. Secant or
tangent pile walls can be constructed in a wide variety of soil conditions, including through
cobbles and boulders.
Sheet Piles
Sheet piling is an earth retention and excavation support technique that retains soil, using

steel sheet sections with interlocking edges. Sheet piles are installed in sequence to design
depth along the planned excavation perimeter or seawall alignment. The interlocked sheet
piles form a wall for permanent or temporary lateral earth support with reduced groundwater
inflow. Anchors can be included to provide additional lateral support if required.
Sheet pile walls have been used to support excavations for below grade parking structures,
basements, pump houses, and foundations, construct cofferdams, and to construct seawalls
and bulkheads. Permanent steel sheet piles are designed to provide a long service life.
Vibratory hammers are used to install sheet piles. If soils are too hard or dense, an impact
hammer can be used to complete the installation. At certain sites where vibrations are a
concern, the sheets can be hydraulically pushed into the ground.
Soil Nailing
Soil nailing is an earth retention technique using grouted tension-resisting steel elements
(nails) that can be design for permanent or temporary support. The walls are generally
constructed from the top down. Typically, 3 to 6 feet of soil is excavated from the top of the
planned excavation. Near-horizontal holes are drilled into the exposed face at typically 3 to 6
foot centers. Tension-resisting steel bars are inserted into the holes and grouted. A drainage
system is installed on the exposed face, followed by the application of reinforced shotcrete
facing. Precast face panels have also been used instead of shotcrete. Bearing plates are then
fixed to the heads of the soil nails. The soil at the base of this first stage is then removed to a
depth of about 3 to 6 feet. The installation process is repeated until the design wall depth is
reached. The finished soil nails produce a zone of reinforced ground.

Soldier Piles & Lagging
Soldier piles and lagging is an earth retention technique that retains soil, using vertical steel
piles with horizontal lagging. Typically, H-piles are drilled or driven at regular intervals along
the planned excavation perimeter. Lagging consisting of wood, steel or precast concrete
panels is inserted behind the front pile flanges as the excavation proceeds. The lagging
effectively resists the load of the retained soil and transfers it to the piles. The walls can be
designed as cantilever walls, or receive additional lateral support from anchors or bracing.
The technique has been used to provide support for many excavations.
Additional Services
1. Earthquake Drains
2. Sculpted Shotcrete
3. Slab Jacking
4. Slurry Walls

5. TRD - Soil Mix Walls
6. Wick Drains
Earthquake Drains
During an earthquake, loose sandy soils have the potential to liquefy, causing great damage
to structures supported by the soil. One solution is to densify the loose soils and/or provide a
drainage path for the dissipation of pore pressures before they reach dangerous levels. In
many cases Earthquake Drains can provide the necessary liquefaction mitigation.
Earthquake drains consist of high flow capacity prefabricated vertical drain wrapped with a
geotextile fabric. Typically the diameter is about 75mm (3 inches). The core is tightly wrapped
with geotextile filter fabric, selected for its filtration properties, allowing free access of pore
water into the drain, while preventing the piping of fines from adjacent soils. The geotextile
wrap is also very durable, and able to withstand the handling and abrasion that occurs during
installation. Several core designs and fabric types can be utilized to suit a variety of drainage
applications and soil classifications.
Sculpted Shotcrete
Shotcrete is a proven, cost-effective and time saving alternative to cast-in-place or pre-cast
concrete. After shotcrete is sprayed onto a surface, often a vertical soil cut reinforced by soil
nails, it can be sculpted and textured in a variety of ways to maintain the look of the
surrounding environment. Options include being screeded flat for a finished look, or the
application of architectural finishes.
Hayward Baker offers aesthetic and architectural shotcrete design and construction across
the country. Projects can range from small landscaping to large landslide and highway cuts.
Our skilled shotcrete technicians and ACI-certified nozzlemen can create natural-looking rock
surfaces as part of a permanent earth retention system. Other applications include structural
shotcrete retrofits for seismic upgrades, sculpted shotcrete for pools, parks, and museums,
and zero lot line permanent basement walls

Slab Jacking
Slab jacking is a re-leveling technique that raises concrete slabs and fills voids, using the
regulated injection of Portland cement grout. Holes are drilled through the concrete slab
through which the grout is injected while monitoring the elevation of the slab surface. The
treatment results in filled voids and a re-leveled and stabilized concrete slab.
Slurry Wall - Cutoff or Structural
Slurry walls are below-grade walls that restrict groundwater flow (cutoff/barrier) or support
excavations and structures (structural diaphragm), using soil-bentonite or cement-bentonite.
For structural diaphragm slurry walls, a clam-shell bucket is typically used to excavate

individual panels that will compose the wall, to design depth. During excavation, soil-bentonite
slurry is placed to prevent caving. After design depth is reached, the slurry is displaced with
concrete pumped through a tremie pipe to the bottom of the panel, and steel reinforcement is
inserted. The finished walls can simultaneously function as a ground water cutoff and soil
retention system during the excavation phase of the project, and then as permanent
underground walls with load-carrying capabilities for the finished structure.
For traditional barrier walls, the trench is excavated through bentonite slurry or cement-
bentonite (CB) slurry to prevent collapse of the trench during excavation. In the case of CB
walls, the CB hardens in the trench to form the wall. When bentonite slurry alone is used, the
excavated soil is mixed with bentonite and then placed back into the trench to form a soil-
bentonite wall. The finished wall results in a groundwater barrier with low permeability.
Non-traditional methods of slurry cutoff wall construction include the vibrating beam method. A
vibratory hammer is used to drive special steel beams to design depth along the wall
alignment. Cement-bentonite slurry is injected during penetration and withdrawal of the beam
TRD - Soil Mix Walls
TRD soil mix walls are mixed-in-place walls that restrict groundwater flow and/or support
excavations, using a specialized vertical cutter post mounted on a base crawler machine. The
vertical cutter post, resembling a large chain saw, is inserted vertically in segments by the
crawler machine until the design depth of the wall is reached. The crawler machine then
advances along the wall alignment while the cutter post cuts and mixes the in situ soil with
cement-based binder slurry injected from ports on the post. The vertical mixing action blends
the entire soil profile eliminating any stratification and creates a soil mix wall with a high
degree of homogeneity and extremely low permeability.

Wick Drains (Prefabricated Vertical Drains, Vertical Strip Drains)
Wick drains, also known as Prefabricated Vertical Drains (PVD) and Vertical Strip Drains
(VSD), are a ground improvement technique that provides drainage paths for pore water in
soft compressible soil, using prefabricated geotextile filter-wrapped plastic strips with molded
channels. A hollow mandrel is mounted on an excavator or crane mast. The wick drain
material, contained on a spool, is fed down through the mandrel and connected to an
expendable anchor plate at the bottom of the mandrel. A vibratory hammer or static method is
used to insert the mandrel to design depth. The mandrel is then extracted leaving the wick
drain in place. The wick drain is then cut at the ground surface, a new anchor plate is
connected to it and the mandrel moved to the next location. A pattern of installed vertical wick
drains provides short drainage paths for pore water, thereby accelerating the consolidation
process and the construction schedule.

• ADDITIONAL SERVICES
•
• ADDITIONAL SERVICES
Earthquake Drains
Sculpted Shotcrete
Slab Jacking
Slurry Walls
TRD - Soil Mix Walls
Wick Drains

Ground improvement techniques

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