Geotechnical and Geodetic Surveys in Shaki

Engineering geological conditions in Shaki

Shaki lies at the foot of the southern slope of the Greater Caucasus, in the transition zone between the mountains and the Alazan–Ayrichay valley. The town stretches along mountain river valleys: its upper part abuts forested slopes, while the lower part sits on broad alluvial fans opening towards the valley. The difference in elevation within the town reaches hundreds of metres, and most streets and plots are on a gradient.

In the foothill belt the ground is made up of proluvial and alluvial deposits laid down by mountain rivers and mudflows: boulders, cobbles and gravel in a sandy-clayey matrix, interbedded with loams and sandy loams. The size and proportion of large clasts in these deposits change over short distances. On the slopes, older rocks — clays, sandstones, conglomerates — are covered by weathering products and clayey slope deposits. Towards the valley the sediments become finer and the share of clayey layers increases.

At the lower edges of the fans, groundwater may emerge at the surface as springs; soils in this belt are wetter and locally waterlogged.

Key construction risks in Shaki

• Mudflow hazard. Mountain rivers crossing the Shaki area can carry debris flows after heavy rain; in 1772 a mudflow destroyed the earlier town, and the present historic centre was rebuilt on higher ground. Near the channel, its former branches and the active part of the fan, construction must be planned around the mudflow path, traces of past events and protective structures.
• Landslides and slope processes. Clayey slope deposits can start moving in the rainy season. Cutting terraced pads into the slope, building retaining walls without drainage and discharging water onto the slope accelerate landsliding.
• Heterogeneous coarse soils. In bouldery and gravelly deposits, conventional drilling and sampling are difficult, and the large clasts make properties vary sharply from point to point. Trial pits and geophysical methods complement boreholes well.
• Wet zones. Spring lines and damp ground at the toe of the fans create a waterlogging risk for buildings with basements and reduce the strength of clayey soils.
• Seismicity. The southern slope of the Greater Caucasus is one of the country's seismically active zones. The design seismic intensity is taken from the applicable standards and codes; on slopes, seismic loading increases the landslide risk.

Surveys typically required

Private houses, guesthouses and hotels are common in Shaki, as is the restoration and refurbishment of historic buildings. The scope depends on whether the plot is on a slope, a fan or in the valley:

• on sloping sites, a topographic survey for designing terraces, retaining walls and surface drainage;
• near mudflow and landslide zones, a geohazard assessment;
• borehole drilling and sampling, combined with trial pits in coarse deposits;
• a seismic survey or electrical resistivity survey to trace the thickness of coarse deposits and the base of slope deposits;
• for historic buildings, a foundation soil investigation and deformation and settlement monitoring;
• in wet zones, flooding risk and drainage recommendations;
• physical and mechanical properties — above all shear tests for slope stability analysis.

In restoring historic buildings, the key question is what soil the existing foundation bears on and whether it can take additional load. A trial pit is dug next to the foundation to record its depth, material and condition and the properties of the soil beneath it. Without this information, no sound decision can be made on adding a storey or rebuilding stone masonry.

How the work is organised

During the site visit we record signs such as traces of past mudflows, cracks on the slope, tilted trees and the condition of retaining walls, and check whether the rig can pass through narrow, steep streets. In historic quarters work is done with compact equipment without damaging existing buildings.

Undisturbed samples usually cannot be taken from bouldery layers; in that case samples come from trial pits or soil properties are assessed by field tests. Undisturbed samples of clayey layers are sent to the laboratory with their moisture preserved. Shaki is a long way from Baku, so equipment transport, several days of crew accommodation and sample shipping can make up a noticeable share of the cost. To complete all field work in one mobilisation, it helps to have as much information about the site as possible in advance — attach photos and the location when you send a quote request.