Engineering Surveys in Absheron: Soil Risks

Engineering geological conditions in Absheron

Absheron district borders Baku to the north-west and north and includes Khirdalan, Masazir, Mehdiabad, Novkhani, Saray and other settlements. The terrain is a low, gently rolling plain: flat interfluves alternate with closed depressions, salt lakes and saline flats, and along the northern coast with patches of wind-blown sand. Within a few hundred metres you can find both a hillside and the bed of a drying lake.

Near the surface, Quaternary marine deposits prevail — sands, shelly sands and sandy loams, loams, and beds of shell limestone. Below them, and in places right at the surface, lie Pliocene clays. Depressions and lake margins hold silty, saline soils with high moisture content. The geology of the peninsula is complicated by fold structures and mud volcanism, so the dip and thickness of strata vary from site to site.

In recent years, intensive private and apartment construction has spread onto former farmland and pasture as well as backfilled saline flats. On such plots an uncontrolled layer of fill often lies on top of the natural soil. A short geotechnical check before buying a plot shows whether it sits on a saline flat or on fill and lets you budget for the foundation in advance.

Key construction risks in Absheron

• Saline soils and aggressive groundwater. Around salt lakes and saline flats, soil salinity is high. Water-soluble salts corrode concrete and reinforcement, and their leaching weakens the soil structure. Chemical analysis of soil and water is therefore practically mandatory here.
• Shallow groundwater and waterlogging. In depressions the water table is close to the surface and fluctuates with the season, irrigation and sewage leakage. In new housing areas without mains sewerage, a gradual rise of the water table is observed.
• Swelling clays. Some Pliocene clays may swell when wetted and shrink when they dry. Foundations and ground-bearing slabs of lightweight private houses are especially sensitive to these movements; swelling potential is determined in the laboratory.
• Mud volcanoes and faulting. Close to mud volcanoes the ground can be heterogeneous, weak and prone to movement. Site selection and the limits of a volcano's zone of influence require a dedicated study in such areas.
• Made ground. Over backfilled saline flats and pits, the thickness of fill changes sharply within a single plot and becomes the main cause of differential settlement.
• Seismicity. Absheron lies in a seismically active zone; the design seismic intensity is taken from the applicable standards and codes and needs refinement on saturated loose soils.

Surveys typically required

A private house needs a small-scope programme, while an apartment block or industrial facility needs a full one. In Absheron conditions the focus is on groundwater, salinity and clay behaviour:

• geotechnical survey for a private house — at least 2 boreholes, samples and a concise report;
• borehole drilling and sampling for larger projects, covering every stratum of the profile;
• study of groundwater level and regime and flooding risk and drainage recommendations;
• chemical analysis of soil and water — salt composition and content, aggressiveness to concrete;
• physical properties, including Atterberg limits and swelling potential;
• on large sites, an electrical resistivity survey to trace strata between boreholes — saline and saturated soils stand out clearly by resistivity;
• for new developments, a UAV (drone) aerial survey and a topographic survey.

How the work is organised

During the site visit we note the previous land use, signs of fill and salinity, and nearby lakes and canals. Most Absheron settlements are easily reached by a drilling rig and truck, but after rain the dirt tracks across saline flats can become impassable, so field work is timed accordingly.

Water samples are delivered to the laboratory quickly so that their chemistry does not change, and undisturbed samples are kept at natural moisture. Because the district is close to Baku, transport is a small share of the cost; the main factors are the number and depth of boreholes, the laboratory test schedule and the duration of groundwater observations. To get a price, send the plot address and the parameters of the planned building via a quote request.