10 Execution documents
10.1 Documents available on site
1) The Brazilian test is run on a cylindrical sample (H/D ratio = 0,5) submitted to compression along a diameter plane and is interpreted in terms of tensile strength of the tested material.
10.1.1 The following documents shall be available on site prior to the main jet grouting works:
- — technical specifications;
- — execution drawings;
- — method statement, if required (see 8.1.5);
- — a geotechnical report describing the subsoil conditions;
- — technical specification of the jet grouting plant;
- — a description of the characteristics of the materials;
- — a report on preliminary tests, where performed.
10.1.2 The jet grouting execution drawings shall contain the following information:
- — the soil profile;
- — the shape of the elements;
- — the number of the elements, a clear reference number for each;
- — the location and orientation of each element, and tolerances on position;
- — the location of possible underground obstructions, services and drainage;
- — the execution sequence, where relevant.
10.2 Documents to be produced on site
10.2.1 Records of the jet grouting execution shall be compiled for future reference. They shall cover for each element:
- — the jet grouting parameters;
- — comments on the spoil return;
- — unexpected features;
- — date and time of execution.
NOTE Examples of site records are given in Annex D.
10.2.2 Where in-situ preliminary trials have been performed, a detailed report shall be prepared, including all the results obtained with reference to the prevailing soil conditions and the size of the jet grouted elements to be constructed.
10.2.3 The jet grouting execution plan and all records shall be kept after the completion of the works.
11 Special requirements
11.1 Compliance with national standards
The execution of jet grouting works shall comply with all national standards, specifications or statutory requirements regarding:
- — security of the site;
- — safety of the working procedures;
- — operational safety of drilling, jet grouting and auxiliary equipment and tools;
- — environmental protection.
11.2 Site safety
11.2.1 Appropriate measures shall be taken to protect the health and safety of the workers and of other people present on and adjacent to the site.
11.2.2 Legislation of European Countries shall be adhered to; health and safety hazards associated with jet grouting shall be assessed on a site specific basis.
11.3 Protection of the environment
11.3.1 Measures shall be taken in order to limit or avoid adverse effects on the environment.
NOTE Attention is drawn to national standards and statutory requirements concerning environmental protection.
11.3.2 The following risks to the environment shall be considered:
- — induced movement in the ground or in adjacent structures;
- — pollution of surface water and groundwater;
- — unacceptable changes in the natural groundwater flow;
- — air pollution;
- — noise.
11.3.3 Methods of handling the spoil, including:
- — collection at the borehole surface;
- — temporary storage on the site;
- — possible treatment;
- — final disposal;
shall be such as to minimise adverse effects on the environment.
Additional design requirements
A.1 The design shall take into account the anticipated stresses in the jet grouted element and the effects of variability of the soil on the strength of the elements.
A.2 The design shall verify the overall stability of jet grouted elements and structures used for underpinning or as retaining walls, including the partial safety concept of ENV 1997-1:1994.
Ranges of jet grouting parameters
The jet grouting parameters usually adopted for the different systems fall within the following ranges:
|Jet grouting parameters||Single fluid||Double fluid (air)||Double fluid (water)||Triple fluid|
|Grout pressure (MPa)||30 to 50||30 to 50||> 2||> 2|
|Grout flow rate (l/min)||50 to 450||50 to 450||50 to 200||50 to 200|
|Water pressure (MPa)||N/A||N/A||30 to 60||30 to 60|
|Water flow rate (l/min)||N/A||N/A||50 to 150||50 to 150|
|Air pressure (MPa)||N/A||0,2 to 1,7||N/A||0,2 to 1,7|
|Air flow rate (m3/min)||N/A||3 to 12||N/A||3 to 12|
|N/A Not applicable.|
The disaggregating effect is obtained by the high velocity of the jet, mainly dependent on the pressure of the fluid used for the disaggregation: grout in single and double (air) fluid systems, water in double (water) and triple fluid systems.
For single and double (air) fluid systems, grout pressure usually ranges between 30 MPa and 50 MPa, as defined in the table above. Lower limits down to 10 MPa have also been adopted in particular cases, such as small diameter jet grouted columns in very loose soils.
NOTE The most recent developments in pumping equipment enable the pressure of the disaggregating fluid to reach up to 70 MPa or flow rates up to 650 l/min.