In order to carry out Geotechnical Surveys and Project Assistance, LURTEK follows different research and development processes depending on the needs of each survey. These processes are:

Cartography: In practically all surveys, the first step in the field research consists of carrying out a geological – geotechnical cartography.

This cartography consists of a superficial survey of the land, taking measurements of the rocky outcrops, regarding their lithology, structure and degree of alteration. In addition we point out the possible accumulations of landfills, ground areas, the existence of landslides, water courses and anything that has an influence on the survey being carried out.

Based on this cartography, the research points necessary to complete the field research are pointed out. These consist mainly of direct methods to research the subsoil and to carry out test pits and/or probes. Sometimes we resort to indirect research methods, which could be geophysics (electrical and seismic tomography, electrical probes, etc.).

Test pits: One of the direct research methods for the subsoil, probably the simplest and cheapest, although also the most destructive, consists of making tests pits with excavators. This technique requires a certain amount of experience in geotechnical engineering as some tests cannot be carried out such as in the case of the probes. Samples can be collected, altered and unaltered, and tests can be carried out with pocket devices. In addition, the vision of the subsoil in a test pit is much clearer than with any other technique, and structural measurements of the rocks can also be made. The research depth is limited to the length of the excavator arm, and it is usually difficult to reach any deeper than 6 metres.

LURTEK uses this technique when the depth required for research is small, when geostructural measurements of the rock need to be taken to make stability calculations, and when the destruction created by the excavation has no influence and can be permitted.

Probes: This is the most usual research method. It consists of perforating the ground and extracting continuous samples. They can go as deep as over 100 metres, and tests of penetration, permeability and other associated tests are done on site, including other tests such as dilatometers, pressure gauges, etc., that allow us to directly obtain geotechnical parameters of the terrain that are very useful for carrying out the calculations. In addition, we also obtain unaltered samples of the terrain, in soil and in rock.

However, it is quite an expensive method and which, except in very special cases, does not provide geostructural measurements of the rock, essential when carrying out stability calculations.

Linked to the probes, DPSH-type dynamic penetrometers or PANDA2- type variable energy light penetrometers, etc. are carried out. LURTEK uses this technique when the features of the terrain require research at a significant depth, or when the level of urban development of the area does not permit the use of a destructive technique such as test pits.

Instrumentation: In some cases it is necessary to carry out instrumentations of the terrain to control certain aspects of the works, as well as the evolution of geological phenomena such as landslides, settlements, etc.

The instrumentation of the terrain is a very broad field. LURTEK has several sets of instrument equipment, such as inclinometers, continuous settlement lines, vibrating wire readout, among others.

Continuous settlement lines are used to control settlements in areas where there are pre-loads or even definitive loads. The aim is to measure the evolution of the settlements, and to compare them to those calculated previously. These measurements manage to monitor the pre-loads, determining their end or the need to increase or decrease the pre-load.

Inclinometers detect horizontal movements on orthogonal axes, to thus determine the depth at which these movements take place as well as their amplitude and velocity.

Lurtek is also prepared to carry out measurements with instruments based on the “Vibrating Wire” technique, such as load and pressure cells, crackmeters, extensometers, etc.

Laboratory: Once the field research has been carried out, and samples have been collected of the different layers of the ground, depending on the needs of the project LURTEK makes a selection of them and plans laboratory tests that provide parameters of the terrain or confirm parameters obtained during the field research. Samples of soil, rock and water are analysed.

All kinds of standard tests are carried out in accredited laboratories.

Geophysics: Sometimes we resort to indirect research methods, which could be geophysics (electrical and seismic tomography, electrical probes, etc.). They are indirect methods that on their own do not have much validity, but when accompanied by direct methods, in some cases they allow you to reduce the number of probe research points, etc., that are economically more expensive.

It consists of using the conductive properties of materials, so that through electrical or seismic pulses, and subsequent readings, different layers can be identified in the ground. For this reason it is necessary to know beforehand what different existing layers there are to associate the readings to the layers already known. In addition they require certain space so that the measurements taken reach a sufficiently reliable depth reading.

These are relatively economical methods, not at all destructive and which allow the research of extensive surface areas. They are very useful in karstified rock where there are cavities, caverns, etc.

LURTEK uses these techniques when direct research of the subsoil is not possible, to reduce the number of direct research points in extensive areas and with very clear lithological differentiation, and in karstified areas.

Office: After collecting the field and laboratory data, and during the office phase, LURTEK carries out the design of the geotechnical calculations necessary for the project, consisting mainly of admissible load calculations, settlements, calculations of structural stability in jointed rock, as well as those that refer to the possibility of circular breaks in soil, altered or massive rocks; as well as push-in pressures, hydraulic gradients for screens and shorings, influence of loads at depth, permeabilities, pre-loads, etc.

To do this it uses the market’s latest software programs, as well as spreadsheets of its own design, and even manual calculations.

Depending on the calculations carried out, all the technicians of LURTEK who have taken part in the survey meet to proceed to the design of the solutions and recommendations of the report, which will finally be used to prepare the Project.

Writing the report: The surveys carried out by LURTEK can be endorsed at the Spanish Official Association of Professional Geologists, at the request of the customer.

As a general rule we provide three bound copies and a CD. This CD is the software version of the Survey carried out by LURTEK, where there are PDF (Acrobat) files attached to be able to visualise or print them.