湖南方运重工科技有限公司 HUNAN FAE HEAVY INDUSTRIES CO.,LTD. TOGETHER WE FORGE AHEAD

Jet Grouting pump

Overview


 

Grouting of soil bodies for strength improvement and/or sealing is a standard method ingeotechnical engineering.

Low pressure injection grouting with solid particle suspensions, chemical solutions or artificial epoxy resins has been in use for some time. It is restricted to soils with certain void ratios and pore sizes. Conventional low pressure grouting uses pressures up to 20 bar to inject grout into the naturally existing pores and voids of a soil. Apart from displacing air or water in pores andvoids with grout, the structure and fabric of the soil remains unchanged. The resulting grout body in the ground is an undefined random structure. Conventionally, fine grained soils can only be grouted with chemical solutions or artificial resins, which increasingly raises environmental concerns.

 


                     




SNS piston mortar pump have features of high pressure, large flow, stable working. They're applied to conveying and plastering various kinds of features and uses of different dry ready-mixed mortar, including various special mortars, gypsum mortar. They're also used for pressure grouting cement slurry and cement mortar. The piston mortar pumps have strong power, smooth pumping, small abrasion, wide range of applications.


They’re applicable for on-site mixing mortar, ready-mixed dry mortar, adhesive mortar, thermal insulation mortar, fireproof mortar, floor surface mortar, self-leveling mortar construction. They're widely used in the dam foundation curtain grouting, slope anchor grouting, holes grouting in tunnel and underground project pile, soil nail wall.


The pump is used to fill cement grout as well as sand grout. It is high in pressure,stable in flow,reasonable in structure and easy for operation. It is applied to grout injection for dam foundation, batholith curtain, slope,tunnel and foundations for other relative reinforcement projects.It can be used to replace mud pump for geological rock core drilling.


Jet Grouting 

 

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 speed of 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 over flows through the drill hole onto the ground surface. This spoil is collected and removed.

 

All materials used in the jet grouting process-water, cement, occasionally bentonite and the soil -- are 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.

 

 

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) compressed air is introduced into the grout jet at its exit point. This adds energy and enables 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 it through a separate jet nozzle situated just below the jet nozzle for the water (Triplex string with triple inner conduit rods). The Triplex-method is an appropriate method for underpinning,especially in cohesive soils.

 

Dimensions

Different geometric forms and dimensions of the soilcrete body can be produced with jet grouting:

■  without rotation of the rods during withdrawal and jetting, cut-off walls of various thickness can be produced;

■  with partial rotation,segments of a cylinder can be produced (bow-tie);

■  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

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