**5.1 Tests in boreholes and excavations**

Geotechnical investigations are performed by geotechnical engineers or engineering geologists to obtain information about the physical properties of soil works and proposed soil foundations for the proposed structures and to fix the distress of earthworks and structures caused by subterranean conditions. This type of investigation is called site inspection. In addition, geotechnical investigations are also used to measure the thermal resistance of soil or backfill materials required for underground transmission lines, oil and gas pipelines, radioactive waste disposal and solar thermal storage facilities. The geotechnical investigation will include surface exploration and subsurface exploration of the site. Sometimes, geophysical methods are used to obtain data about sites. Subsurface exploration usually includes soil sampling and laboratory testing of recovered soil samples.

Some of the on-site tests are: standard penetration test, dynamic cone penetration test, cone penetration test [7, 21].

### **5.2 Engineering geophysics**

Engineering geophysics consists of the spatial studies of the Earth's surface and subsurface. The geophysical signal is measured, processed and analyzed in order to discover anomalies in the subsurface and determine the composition and physical properties of rocks, layers, etc. This information is essential in engineering planning, calculations and infrastructure project design, energy and environment [8, 22].

Use of geophysical methods to obtain information for civil engineering. The goal is usually to describe not only the geometry of the Earth's interior but also its nature

(for example, its elastic properties as determined by measurements of seismic velocities and density). Shallow, gravitational, magnetic, and electrical seismic reflection and refraction methods and sampling methods are commonly used to find bedrock depth and sediment strength for foundation purposes, to determine the rupture (qv) susceptibility of rocks, to measure the degree of rupture, to detect underground cavities, to detect pockets of gas near the surface, to determine The dangers of buried pipelines under the sea floor, buried pollutant barrels, and landfill safety. In water-covered areas, high-powered sphygmomanometers, sparks, gas pistols, and other seismic reflection methods employ high frequencies (up to 5 kHz) to obtain reflections from shallow façades so that bedrock and the nature of the filling material can be diagnosed. Such methods are also used to locate large pipelines on the sea floor or to bury them on the sea floor by the prominent deflections they generate. It is usually limited to a shallow breakout of over 1,000 feet [22].
