• Ε 106- 86

• ASTM D4622 – 86

• DIN 4014

• Ε 102 – 84
• ASTM D4395

• ASTM D4403
• ISRM DOC. 5/1997

This type of test is performed during drilling of the borehole and records the resistance to penetration of a standard split-spoon cylindrical samples pushed in the ground from the bottom of the borehole by blows. The recorded N value is the number of blows necessary to achieve penetration for 45cm by a hammer of weight 63,5kg falling from 76,2cm in three successive steps of 15cm each.
The test is widely used to determine in-situ properties of the subsoil and indicatively:

• the relative density of soil formations
• the resistance to penetration of the soil formations
• the shear resistance parameters and indirectly the compressibility parameters of soil formations (by semi-empirical correlations)
• the determination of the foundation bearing capacity and settlements
• the determination of piles bearing capacity

This type of test is performed during drilling and monitors the undrained shear resistance of the subsoil, mainly on soft to stiff clays. Within the drilled hole, a rectangular vane consisting of four plates fixed at 90o to each other is intruded by push in the soil layers, followed by rotation of the metal column and the vane. Records of the monitored torque till failure allow the determination of the undrained shear strength of the subsoil formation.

Site measurement of subsoil permeability is mainly performed within a borehole by recording the variation of the water level through variable, falling head tests (Maag) or constant head tests (Lefranc). These tests are applicable in soil-type formations. During the Maag type test, the borehole is completely filled up and the rate of decreasing water level is monitored. During the Lefranc type test, the filled-up borehole is kept constant and the water supply rate is recorded to assume for a steady – constant water level.
Based on those records, the permeability coefficient is obtained.

Within rocky formations, permeability tests of Lugeon type are performed to determine the permeability coefficient of the rock-mass and its discontinuities. During this test type, the absorbed water supply within the tested part of borehole is recorded at various pressure steps in both increasing and decreasing order in relation with time. Based on those records, the rock mass permeability coefficient is obtained.

The aim of Pumping tests is to identify the hydraulic parameters of the aquifers (k: permeability coefficient, T: transmissitivity coefficient, S: storage coefficient) (“aquifer test”). During pumping tests, water is pumped from a well and water level drowdown is measured in the well and in nearby observation points (wells, piezometers). Pumping tests also provide information about the well (“well tests”). Aquifer tests are used to solve problems about the flow of underground water, the yield of aquifers, the transport of pollutants e.t.c. Well tests are used to calculate specific yield of wells, to check well construction quality and development by calculating the linear and nonlinear load losses, the estimated cost of pumping groundwater etc.

These field tests are performed in accordance with BRE Digest 365 (Soakaway Design Recommendations) of part H3 of approved document H “Drainage and waste disposal” of the Buildings Regulations 2000, to obtain soil infiltration rates for soakaway design.
The test is simulating water flowing out of the soakaway and into the ground using a special test pit or water – borehole in order to determine a value for the infiltration characteristics of the soil. The infiltration rate is calculated from the time taken for the water level to fall from 75% to 25% effective storage depth in the pit.

Pressuremeter tests are performed in boreholes, in accordance to the general rules and directives of the relevant Greek Ministerial Decision FEK 366/24-6-83, that agree to the respective French Specification NFP94-110 “Ménard Pressuremeter test”, the American Specification ASTM D4719-20 “Standard Test Methods for Prebored Pressuremeter Testing in Soils”, as well as the European Specification EN ISO 22476-4:2021, “Geotechnical investigation and testing – Field testing Part 4: Prebored pressuremeter test by Ménard procedure”.

• TH. TASSIOS
• K. DEMIRIS

• Magnetic