Engineering Geology: What Surveys You Need Before Designing a Foundation

A foundation is never designed from a “standard template” — it is designed for a specific soil. The same two-storey house sitting on solid limestone versus on a collapsible loam will need completely different structural solutions, and the cost difference can be several-fold. So that the designer knows what the building actually rests on, geotechnical (engineering-geological) surveys are carried out before the project is developed. In Aktau and across Mangystau Region this matters even more: saline soils, a high groundwater table near the Caspian, and an environment that is aggressive to concrete make “eyeballing it” a direct route to cracked walls within two or three seasons.

In this article we break down exactly which surveys are required before designing a foundation, how they work, and what drives their scope.

Why Geotechnical Surveys Are Needed

Geotechnical surveys are a set of field and laboratory works that answer the designer’s key questions:

• which layers the subgrade is made of and at what depth the bearing layer lies;
• the soil’s bearing capacity (how much load it can take without unacceptable settlement);
• where the groundwater table is and how it shifts seasonally;
• whether the environment is aggressive to concrete and steel;
• whether hazardous processes are present — collapsibility, swelling, salinity, seismicity.

Without this data, a foundation design is either over-reinforced “to be safe” (and the client overpays for excess concrete and rebar) or the conditions are underestimated — and then the building suffers uneven settlement, cracks and tilt. Surveys are almost always cheaper than rebuilding the foundation of an already-constructed object.

Under Kazakhstan’s regulations (SP RK 1.02-102 “Engineering Surveys for Construction”), geotechnical surveys are mandatory for all permanent structures — from a private house to an industrial facility. Without a survey report, the project will not pass state expert review.

What the Surveys Include

1. Drilling Geotechnical Boreholes

The core method. A drilling rig sinks boreholes within the building footprint to expose the soil profile to the required depth. From the boreholes the geologist logs each layer and collects samples.

The number and depth of boreholes depend on the building type and site complexity. As a rough guide:

Object	No. of boreholes	Depth
Private house, up to 2 storeys	3–4	6–10 m
Multi-storey residential building	5–9	15–25 m
Industrial building, tank	5+, on a grid	15–30 m
Linear object (pipeline, road)	every 50–200 m along the route	3–8 m

The depth is set so as to pass through the compressible layer — the layer that actually carries the foundation load — and to capture the bearing layer below it.

2. Cone Penetration Testing (CPT)

A cone is pushed into the soil at a constant rate while sensors continuously record the resistance at the tip and along the side. The method gives a detailed strength profile of the soil without sampling and complements drilling well, especially in sands and clays. CPT is faster and cheaper than drilling, so it is often combined with boreholes: drilling for logging and samples, CPT for a continuous strength characterisation.

3. Sampling and Laboratory Soil Testing

Samples from the boreholes go to a soil laboratory, where the following are determined:

• physical properties — moisture content, density, grain-size distribution, plasticity index;
• strength and deformation — angle of internal friction, cohesion, deformation modulus (oedometer and shear tests);
• chemical analysis — salinity, the aggressiveness of groundwater to concrete (sulfate aggressiveness in particular — critical for Mangystau).

It is the laboratory data that gives the designer the numbers the foundation is calculated from. Field logging without the laboratory is only half the job.

4. Hydrogeological Observations

The geologist records the groundwater level in the boreholes and forecasts its seasonal fluctuation. For Aktau and the coastal zone this is one of the key items: a high and aggressive water level directly affects the type of waterproofing and the concrete’s water-resistance grade.

5. Geophysical Methods (When Needed)

On complex sites, electrical or seismic surveys are added — to trace the top of the rock layer, detect karst, or identify loosened zones between boreholes. For ordinary construction this is usually not required.

Complexity Categories and Survey Scope

The scope of work depends on the complexity category of the geotechnical conditions:

Category	Conditions	What it means for the surveys
I — simple	Uniform layers, flat terrain, deep water	Minimum number of boreholes
II — medium	2–4 layers, variable thickness, water within foundation depth	Standard scope
III — complex	Collapsible/saline/swelling soils, high water, seismicity	Increased scope, extra tests

Most sites in Mangystau Region fall into category II–III precisely because of salinity and hydrogeology — this needs to be built into the budget and schedule in advance.

The Specifics of Aktau and Mangystau Soils

The Caspian region has several characteristic features that directly affect the foundation:

• Saline soils. When wetted, salts leach out and the soil produces additional collapse. An assessment of relative collapsibility on soaking is required.
• Aggressiveness to concrete. A high sulfate content in groundwater destroys ordinary concrete. Sulfate-resistant cement and an elevated water-resistance grade are needed — this is determined by chemical analysis.
• Rocky limestones. On a number of sites the bearing layer is strong limestone at shallow depth, which allows shallow foundations to be used. But the top of the rock is often uneven, and without drilling its position cannot be predicted.
• Seismicity. Part of the region’s territory falls within seismic zones — this is accounted for both in the surveys and in the foundation calculation.

These factors are why “imported” standard solutions from other regions perform poorly in Aktau. On-site surveys are mandatory.

What You Receive as the Result

The outcome of the surveys is a technical report on the geotechnical surveys. It includes:

• geological-lithological cross-sections and borehole columns;
• tables of physical and mechanical properties for each geotechnical element;
• CPT and laboratory test results;
• groundwater data and its aggressiveness;
• conclusions and recommendations on the type and depth of the foundation.

It is this report that the designer uses as input data, and it is this report that is checked during the state expert review of the project.

What Affects Timelines and Cost

1. Building type and size — the more load and floor area, the more boreholes and the deeper the drilling.
2. Soil complexity category — category III requires additional tests (collapsibility, chemistry, seismicity).
3. Site accessibility — remote sites in Mangystau add time and cost for mobilising the drilling equipment.
4. Volume of laboratory work — a full test suite is more accurate but costs more than the minimum.

For a private house within Aktau, the field stage usually takes 1–2 days, with the laboratory and office processing adding another 1–2 weeks. For a large industrial facility the timeline stretches to several weeks.

Conclusion

Geotechnical surveys are not a formality for the sake of expert review — they are the input data without which a foundation cannot be designed correctly. In the conditions of Aktau and Mangystau Region, where soils are saline, water is aggressive, and the rock-base relief is uneven, cutting corners on surveys almost always turns into problems during operation.

GeoProGlobal carries out geotechnical surveys in Aktau, Zhanaozen, Beyneu and across Mangystau — from drilling and CPT to laboratory testing and a finished technical report for design. If you are planning construction and need to understand the conditions on a specific site, get in touch — we will tailor the optimal survey scope to your project.