In-Situ Investigations

Continuous core drilling is performed with the help of Specialized Drilling Rig, which have the following technical features:

Drilling depths up to 70 m (average depths of 20-30 m)
Drilling diameters range between 80 mm and 127 mm
The drilling equipment allows a minimum recovery rate of 80%, and undisturbed sampling (A and B category)
Use of Thing Wall Samplers (Shelby) ensures the collection of high quality samples (class 1-2)
Wet core drilling is performed only in the case of cemented rocks and soil

This type of drilling is recommended in the case of complex projects (like for instance, motorways, apartment buildings, industrial facilities, stabilization works, etc.). Moreover, this procedure is the base of securing geotechnical parameters (physical and mechanical), as required to conduct a geotechnical designing process.

Nordmeyer-Geotool, a dynamic penetrometer presents the following technical features:

They allow exploration works to be performed at depths of maximum 6 to 8 m
Collection of disturbed samples (category: C)
The drilling window samplers advance telescopically
Diameters range between 80 mm and 32 mm

It is recommended for small buildings, infrastructure works, preliminary studies of site aimed to host projects that are more complex.

In-situ Dynamic Penetration is used to establish the strength of a soil or of a soft rock upon the dynamic penetration of a cone.
In order to drive the cone into the ground, a hammer of a stated weight and from stated height is dropped. The penetration strength is defined as the number of blows required to drive the penetrometer on a defined length, in our case 10 cm. This needs to be constantly recorded, depending on the depth. No samples are collected.
Depending on the technical features of the machine, the dynamic penetration is classified as follows:

The company uses the GeoTool LSMR vk, a dynamic penetration tool to conduct these tests. The results of the dynamic penetration tests are correlated with the results obtained from drilling works, but the most relieble ones being the tests conducted on non-cohesive soil (granular type).
Standard: SR EN ISO 22476-2 Dynamic probing. [2006]
Results: the processing of recorded data (number of blows) collected during the test, leads to the establishment of the relative density index of the soil (Id – [%]) and an approximation of the internal friction angle (φ – [°]). These results are valid only for non-cohesive soils.

The standard penetration test is used to:

Measure the resistance to dynamic penetration of a core tube (a sampler)
collect a disturbed sample, so as to allow identification of the soil type

The penetration resistance is measured based on the necessary blows (N) for 300mm, after fixing depth (150 mm), i.e. the test is conducted at 450mm depth.

Standard: SR EN ISO 22476-3 Standard penetration test [2006]
Results: The number of blows N must be correlated with coefficients that are considering different other factors (like rods length, depth, borehole diameter, etc.), and in this manner Ncor is obtained. The followings are being determined by considering this value:

Non-cohesive soils: thickening level of soils (Id [%]) and internal friction angle (φ [°])
Cohesive soils: strength to compression under non-consolidation status (qu [kPa])

The Cone Penetration Test (CPT) is establishing the soil and soft rocks strength upon penetration of a cone, together with the local friction on the sleeve. The Cone Piezo-cone Test (CPTU) is in fact a Cone Penetration Test that is using an electric cone, and includes some additional instruments aimed at establishing pores water pressure.
The raw data recorded during the CPTU are set forth below:

Penetration strength of the cone
Local friction on the friction sleeve
Pores water pressure

Standard: SR EN ISO 22476-1 Electrical cone and piezocone penetration test [2012]
Results: The interpretation of the raw data is based on several methods recommended by relevant literature, leading to the results being divided in three main types:

Identification of penetrated soil types, by considering their behaviour (response type) (SBT – soil behaviour type)
Estimate of certain geotechnical properties (SPT, permeability coefficient, OCR, un-drained shearing strength, etc..)
It can be used to simulate designing solutions (foundations sizing, calculation of micropiles)

Hydrogeological explorations are conducted so as to assess the soil and subsoil pollution levels, by considering the hydrodynamic connections of the systems in which water travels, due to the fact that water is the main agent for transferring pollutants.
Minimum works required for a hydrogeological exploration are:

Data processing shall be in correlation with the density of the performed explorations and the specific methods used in practice, being aimed at improving the integrated interpretation of all data, assessments of the explored pollution.

The soil exploration conducted by advancing environment related boreholes is focused on learning the geological structure, identifying and following all elements required for characterizing the explored geologic environment.

Together with the advancement of the continuous or intermittent core boreholes, the documentation thereof is performed by establishing the lithological succession, correlating different formations, and identifying hydrostatic and pollutants levels.

The laboratory tests conducted on the collected samples are in general geo-chemical analyses, doubled by the geo-technical tests (physical mechanical, mineral and petrographic tests), being essential for learning the actual geology of the area hosting the underground pollution.

The quality of ground waters, and their associated fluids, being polluted or not, and the quality of soils are all established by collecting water samples from the works (hydrogeological boreholes, wells, piezometers, etc.) and through their physicochemical analyses at certified laboratories.

The level of the pollution is established by comparing them with the warning or response levels provided under relevant current in force legislations, but also with the levels of natural geo-chemical levels of such ground waters.