5.10 Compaction testing of soil

5.10.1 Scope

(1) This standard covers compaction tests (Proctor tests) and the California Bearing Ratio test.

NOTE Annex R provides a guideline for the minimum number of samples to be tested for one stratum, as well as additional information on the test and its evaluation.

5.10.2 Compaction tests

5.10.2.1 Objective

(1) Soil compaction tests (Proctor tests) are used to determine the relationship between dry density and water content when a given compaction effort is applied.

5.10.2.2 Requirements

(1)P The following shall be specified or checked:

  • the handling of soil with oversize fractions;
  • the treatment of stiff finesoil;
  • the specimen preparation and maturing;
  • the testing procedures and compaction effort to be applied;
  • whether the equipment (moulds and rammers) used is as specified in the standard(s).

(2) The option of carrying out in-situ tests instead of laboratory tests should be considered for special types of soil.

5.10.2.3 Evaluation and use of test results

(1)P The compaction characteristics of soil shall be reported together with grain size distribution curves and proportion of oversize material by dry mass with correction, if appropriate.

(2) The optimum water content (wopt) and the corresponding maximum dry density achieved under the applied compaction effort (ρd,max) can be used in evaluating the quality of compacted fills.

5.10.3 California Bearing ratio (CBR) test

5.10.3.1 Objective

(1) The objective of the test is to determine the California Bearing Ratio (CBR) of a compacted or undisturbed sample.

(2) The CBR value is obtained as the percentage of the standard load corresponding to the standard penetration, when a cylindrical plunger of a standard cross-sectional area is made to penetrate into the soil material.

5.10.3.2 Requirements

(1)P The following shall be specified or checked:

  • the method of preparation of each test specimen;
  • how many tests are to be run in a set of test specimens;
  • the handling of soil with oversize fractions (D > 16 mm);
  • the maturing of specimens;
  • whether or not a specimen is to be subjected to soaking;
  • if soaking is used, whether swelling is to be measured;
  • the surcharge to be applied for soaking and for testing;
  • the water content at which compacted specimens are to be prepared;
  • the specimen dry density or compactive effort;
  • whether equipment (moulds and rammers) used is as specified in standard;
  • whether or not the test is to be carried out on one end or both ends of the specimen.

5.10.3.3 Evaluation and use of test results

(1)P The CBR test results shall be reported together with grain size distribution and proportion of oversize material by dry mass, if relevant.

(2) The CBR value can be used as a basic parameter for the design of flexible pavements. It can be used to evaluate the potential strength of sub-grade, sub-base and base course materials (including recycled materials) for supporting road, railways and airfield pavements.

5.11 Permeability testing of soil

5.11.1 Objective

(1) The objective of the test is to establish the coefficient of permeability (hydraulic conductivity) for water flow through water-saturated soil.

5.11.2 Requirements

(1)P When determining the coefficient of permeability of a soil stratum, the following items shall be considered:

  • the preferred test type for permeability determination;
  • the orientation of the specimen;
  • the need for additional classification tests.

NOTE Further information on a procedure, presentation and evaluation of the permeability test can be found in CEN ISO/TS 17892-11, (see X.4.7).

(2)P Depending on the conditions where the test results will be used, the following shall be specified:

a) In clay, silt and organic soil:

  • the stress conditions under which the specimen is to be tested;
  • the criterion for achieving and maintaining the steady-state flow condition;
  • the direction of flow through the specimen;
  • the hydraulic gradient under which the specimen is to be tested;
  • the need for back-pressure and the required degree of saturation;,
  • the chemistry of percolating fluid.

b) In sand and gravel:

  • the density index to which the specimen is to be prepared;
  • the hydraulic gradient under which the specimen is to be tested:
  • the need for back-pressure and the required degree of saturation.

(3) The hydraulic gradient in the laboratory should be close to that in the field, unless otherwise required due to a particular problem.

(4)P When selecting the hydraulic gradient, it shall be checked that the gradient in the laboratory test and the gradient in-situ lie within the domain of application of Dairy's law.

(5) The report should indicate any known deviation from the standard testing procedure, for example in the degree of saturation of the test specimens, testing procedures, composition of the specimen or in any other aspect.

(6) For permeability tests on clay, silt or organic soil, only soil specimens of Quality Classes 1 or 2 should be used.

(7) For sand and gravel materials, specimens of Quality Class 3 and remoulded or re-compacted soil samples may be used.

(8) It should be checked that the volume changes due to the consolidation of the specimen shall only negligibly affect the measured permeability.

NOTE Annex S provides a guideline for the minimum number of samples and tests for one stratum, as well as additional information on the test and its evaluation.

5.11.3 Evaluation and use of test results

(1) The evaluation should assess:

  • the extent to which the boundary conditions (degree of saturation, direction of flow, hydraulic gradient, stress conditions, density and layering, side leakage and head loss in filter and tubing) affect the test results;
  • how well these conditions match the situation in the field.

(2) For partially saturated soil, much smaller values may be relevant than the values measured in the case of full saturation.

(3) Due consideration should be given to whether a temperature correction should be applied.

(4) The coefficient of permeability can be computed from the test data under the assumption that Dairy's law is valid.

(5) The coefficient of permeability can be used in design of excavations and earth dams to estimate the amount of seepage, to assess the feasibility of groundwater level management (lowering), to design the sheet pile walls, to estimate seepage pressures, etc.

Eurocode 7: Geotechnical design — Part 2: Ground investigation and testing