To provide information of the ground on which the building relies , geotechnical investigations are conducted which aim is determining the spatial position of soil layers, their thickness, extent and depth of the groundwater table. It also determines the type of material (identification and classification), engineering properties (strength, deformability, water permeability, workability).
Field studies performed by our company are the following:
hand set for probing and Machine-set type 150 and type GDR Longyear 38 with continuous coring,
Boring is used in nearly all types of soil, it is easily performed and the emergence of groundwater does not cause greater tie-ups in work.Boreholes can be performed with:
hand set (probing),
Boreholes are used for:
determination of groundwater levels,
pore pressure measurement (monitoring wells),
determination of water permeability of layers (pumping, filling),
measurement of other soil parameters (pressure meter, plate) - probing penetration,
standard penetration tests (SPT),
static penetration (CPT).
Hand set for probing
Hand set is used for drilling because of its light weight, mobility and the speed of operation is well suited for use in rugged terrain, limited in terms of height and urban areas. It is used for preliminary studies for the purpose of funding the light building . The depth of exploration borehole that can be achieved when using hand set is up to 12m, provided that the walls of the borehole are stable. In, coarse materials particulary below the groundwater table, drilling probe is limited or impossible. Hand set for exploration drilling consists of a tripod (tower) with a winch, a rope slung over a pulley at the top of the tripod and connected to the drill pipe. At the end of the drill bars various tools for drilling and sampling can be attached.
When it is necessary to perform deep exploratory boreholes, over 12m, as well as in incoherent areas and in the marble rocks we use:
machine-set type GDR 150 with continuous coring, Φ 131/101mm,
machine-set type LONGYEAR 38 with continuous coring, Φ 116/101mm in solid rock mass.
Probing penetration is an supporting probing and is performed in order to obtain the relative resistance of the soil. It is useful in cases where the ground is soft and muddy and when it is not possible to collect undisturbed cohesionless soil samples from greater depths for testing their strength and compressibility. According to the method of execution we can distinguish standard (dynamic) and static (penetration) probing.
Standard dynamic penetration test SPT
Standard dynamic penetration tests are carried out during boreholes drilling. These tests were performed using a 30.50cm rod, which was driven using a 0.63kN hammer. Standard penetration is performed using a spike length 30.50cm, which is driven using a 0.63kN hammer. In the course of the test, the hammer was falling from a height of 76.30cm. The dynamic penetration tests were performed in the previously cleaned bottom of the borehole. In 3 successive 15 cm increments the number of blows was counted. Based on the number of blows, the top 15cm is discarded while the following two are summed up.
Static penetration test CPT
The static penetration device consists of a conical tip with a diameter of about 35mm with sides sloping at about 60°. In the upper part, the tip is extended with a full metal extension 20mm in diameter, located in a sleeve about 25mm in diameter. The tip is pushed into the soil using static force produced by hydraulic and mechanical crane. The crane pushes into the upper cross-girder. Thus produced force is transmitted through the extension and the tip to the ground into which the tip is being pressed. The penetration speed is regulated so that it is constant and ranges from 0.2 to 0.4m per minute. In this process, measurements are taken of total resistance of the tip and the sleeve, and of the tip separately, by reading the pressure gauge for a particular penetration depth of the tip.
Installation of piezometric structures
Piezometers installed in order to establish and monitor the groundwater level fluctuations during the construction and exploatation of facilities.
Piezometric structures are made of plastic tubes, which consist of a solid part, a perforated part and a precipitator. When the installation of pijezometarskih construction is completed, we performe filling with gravel granules.