Geotechnical Site Investigation in Lankaran

Engineering geological conditions in Lankaran

Lankaran lies in the south-east of the country on the Lankaran lowland, which stretches between the Talysh Mountains and the Caspian Sea. The town and its surroundings occupy an almost flat surface sloping gently towards the sea, while to the west the terrain rises within a short distance to the forested Talysh foothills. The lowland is crossed by the Lankaranchay and other mountain rivers, whose lower reaches include low-lying areas that flood from time to time.

The lowland is underlain by Quaternary marine and river deposits: clays, loams, silty sandy loams, fine and silty sands. Marine sands and shelly layers occur along the coast, while depressions and abandoned channels may contain silty soils with organic content. Closer to the foothills, gravelly fan deposits and slope loams appear in the profile. Clayey soils often have high natural moisture content and a soft to very soft consistency.

Lankaran is the wettest region of the country: annual rainfall here is several times higher than on Absheron, which directly governs groundwater recharge and the condition of the soils.

Key construction risks in Lankaran

• High groundwater. Across most of the lowland the water table is very close to the surface and rises further in the rainy season. This complicates excavation, requires dewatering and makes basements and underground rooms risky without robust waterproofing and drainage.
• Soft clayey soils. Saturated clays and loams have low strength and high compressibility. Buildings on such ground may keep settling for a long time, and the settlement becomes uneven as loads increase. Piles or ground improvement are sometimes required.
• Soils with organic content. Silty and peaty soils in former channels and marshy areas may be unsuitable as natural foundation soil; their extent must be established in advance.
• Waterlogging and floods. River overflow, ponding of rainwater on the lowland and fluctuations of the Caspian level cause waterlogging in low areas. Ground elevations and site drainage are among the basic inputs for site planning.
• Humid climate and aggressiveness. Constant humidity accelerates corrosion of concrete and steel structures, and groundwater chemistry may be aggressive depending on the site.
• Seismicity. The Talysh zone is also seismically active. The design seismic intensity is taken from the applicable standards and codes; saturated soft soils amplify seismic shaking.

Surveys typically required

In Lankaran, hydrogeological questions are inseparable from geotechnical ones, so both types of survey are usually commissioned together:

• borehole drilling and sampling, taking undisturbed samples of soft clays with special samplers;
• cone penetration testing (CPT) — particularly informative for the thickness of soft layers and pile capacity;
• groundwater level and regime, with a forecast of seasonal fluctuations;
• flooding risk and drainage recommendations and permeability tests for excavation dewatering;
• aggressiveness of groundwater and soils;
• mechanical properties — oedometer and shear tests, assessment of long-term settlement of soft clays;
• in low-lying areas, a topographic survey with accurate elevations and settlement monitoring.

The report should give not only the measured but also the predicted maximum groundwater level, because a reading taken in the dry months does not reflect conditions in the rainy season. This forecast determines the feasible basement depth, the type of waterproofing and whether a drainage system is needed.

How the work is organised

Timing of field work is especially important in Lankaran: during long rainy spells rural roads and fields become impassable for heavy equipment, and boreholes fill with water quickly. The site visit checks access, how dry the pad is and nearby canals. To measure the stabilised level correctly, the borehole has to be left for a period of time, which is built into the schedule.

Soft clay samples are easily disturbed in transit, so they are packed to protect them from vibration, and water samples are delivered to the laboratory promptly before their chemistry changes. Lankaran is far from Baku, so equipment transport and crew accommodation are added to the cost; combining several projects reduces this share. Send the site location and a description of the planned building via a quote request.