FAE Jet Grouting
What FAE jet grouting could offer?
Jet Grouting or High Pressure Grouting can be employed in all soils
from clays to coarse gravels irrespective of grain size distribution, void
ratio or pore sizes. Jet grouting uses a high pressure jet(approx. 400 bar) to cut the natural soil in order to mix and partially replace it with the
grout. This creates a "soilcrete" body whose strength and/or permeability characteristics are independent of the original soil fabric.
To construct a jet grouted column, a small diameter bore is drilled with
the jet rods and drill bit down to the design depth. Drilling gear and drill fluid are chosen to be appropriate for the soil type. To increase the
diameter of the jet grouted column and to optimize usage of cement and efficiency in dense, cohesive or very compact soils, pre~cutting with
high pressure water may be employed during the initial drilling.
As soon as the design depth has been reached, the rods and drill bit are
slowly withdrawn from the soil. During the withdrawal, grout is injected at high pressure (approx. 400 bar) into the soil from jet nozzles which
are situated horizontally just above the bottom of the drill bit. The speedof particles in the jet is approx. 200m/s. Because the drill rods and drill bit are kept rotating during withdrawal and jetting, a homogenous
cylindrical body is produced consisting of a mix of injected grout and
displaced soil.
Form and size of the jet grout body can be influenced by varying jet
pressure, withdrawal rate and rotation of the jetting gear.
Some of the soil~grout mixture overflows through the drill hole onto theground surface. This spoil is collected and removed.
All materials used in the jet grouting process~water, cement, occasionally bentonite and the soilare natural inert materials which have no
negative impact on groundwater and environment.
Jet grouted columns can be executed as vertical columns or in any
inclination.
Specifications | |
Veriable Displacement | 0-150 lit/min |
Pressure | 35 Bar |
Inlet Diameter | 64mm |
Outlet Diameter | 32mm |
Power | 11KW |
Weight | 450kg |
Jet Grouting Methods
FAE uses three different methods for jet grouting:
Simplex-Method
Cement grout is injected into the soil with high pressure (approx. 400 bar) at the drill head (monitor). The jet cuts the soil and mixes it thoroughly with the grout. The Simplex~method is appropriate for shallow depths and horizontal jet grouting.
Duplex-Method
Using special rods with double inner conduit (Duplex string) compressedair is introduced into the grout jet at its exit point. This adds energy andenables the Duplex~method to reach much greater depths and achieve
larger diameters than the Simplex-method.
Triplex-Method
The Triplex~method uses a high pressure water jet with compressed air
to cut the soil. Cement grout is introduced into the soil and mixed with itthrough a separate jet nozzle situated just belowthe jet nozzle for the
water (Triplex string with triple inner conduit rods). The Triplex~method isan appropriate method for underpinning, especially in cohesive soils.
Dimensions
Different geometric forms and dimensions of the soilcrete body can be
produced with jet grouting:
1~without rotation of the rods during withdrawal and jetting, cut~off
walls of various thickness can be produced;
2~ with partial rotation, segments of a cylinder can be produced (bow-tie);
3~with full rotation, a cylindrical body is produced; diameter of the
cylinder can be changed by varying withdrawal rate and/or jet pressure.
Jet Grouting Parameters
Jet grouting parameters which are chosen for a given project depend on the required characteristics of the finished product, the geotechnical
characteristics of the soil and the chosen jetting method.
Principle jet grouting parameters are:
~withdrawal rate of the jet string
~ rotation speed of the jet string
~ flow rate of the grout
~ jet pressure
~ jet volume
~ number and diameter of jet nozzles
~ volume and pressure of compressed air
~ mix design of the grout
Applications of Jet Grouting
~ underpinning of existing structures
~ downward extension of foundations in the case of settlements or
increased load
~soil improvement, even underneath existing structures
~ vertical impervious barriers
~ impermeable base for excavations
~ bracing and stiffening of excavations underneath their base
~ connection of sealing walls to existing structures and/or services and
utilities
~ walls for cylindrical or polygonal excavations
~ horizontal screens and canopies for tunneling
~ soil stabilisation between neighbouring excavations or foundation
works
~ impervious connection of individual piles in pile walls
What are FAE jet grouting methods?
What are FAE jet grouting delivery?
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