We are all familiar with soil and how important it is to any kind of construction project. The houses we live in, the offices we work from, the roads we use to move from one point to another etc, just to name a few. All this depend highly on the soil we see and walk on every day. Often, by just using our eyes one can quickly tell whether the soil is sand, clay, gravel, silt, peat, rock or loam. However, we can never tell whether the type of soil we just identified with our eyes can sustain and bring to life a proposed structure from building architects and infrastructure design engineers. Therefore, this is where soil testing comes in. It is the most important procedure to conduct before any construction project commences at a particular site with a particular type of soil identified.
Why Soil Testing Is Non-Negotiable
“It is important to check the quality of soil before you build your project (road/pavement/construction etc.). The ground where you are planning to make your project it is important to check the soil quality of it before your construction work begins,” remarks Chris Muya MD at Measurement Systems Ltd.
Engineering Insights from Soil Analysis
In David Adede’s view, Director at Rock Link Geological Consultants Ltd, “Soil testing gives the engineering properties of the formation upon which the construction will be based. Engineers design the construction based on the properties of the soil or rock identified through geotechnical investigation. Test results play a critical role in determining the type and depth of the foundation, the materials to be used, and the structure’s height, size, and load capacity.”
Risks of Skipping Proper Soil Testing
Failure to test site soils adequately and correctly can cause critical levels of financial and safety risks. It is therefore very important to understand the soil properties and make use of the acquired information in the planning and designing of the project phases.
Lessons from Structural Failure: The Leaning Tower Case
A good example of soil failure is the leaning tower of Pisa located in Italy in the city of Pisa. Originally, it was designed to stand at 60 meters. However, the current height measurements of the tower stands at 56.67m =highest side; 55,86m =lowest side. The tower has recorded a nearly four-degree lean. This was as a result of an unstable foundation. Poor soil testing analysis or no tests were conducted at all may have contributed. Eventually, it was until the 1920s the foundations of the tower were injected with cement grouting that has stabilized the tower to some extent.
Key Factors Determined Through Soil Testing
“Soil test is very important step before construction begins.
If project teams fail to conduct soil testing, they expose the project to potential failures and unforeseen risks, which could ultimately lead to fatal outcomes,” emphasized Muya.
He added that soil testing primarily evaluates the ground’s bearing capacity while also analyzing its chemical and physical composition. The soil must be strong enough to support the weight of the proposed structure. Beyond bearing capacity, soil quality plays a critical role in ensuring structural stability. Several factors influence soil quality, including weather patterns, climate change, and the historical use of the land.
He further explained that engineers determine the length and depth of foundation pillars based on soil conditions. Soil testing also establishes the water table level and guides the selection of appropriate construction materials. This ensures the structure’s durability and performance. For example, if due to moisture the area is prone to corrosion then it is important to choose only corrosion resistant re-bars for the construction. Alternatively, one can use necessary additives to inhibit corrosion,” he elaborated.
Common Soil Testing Methods in Construction
Some of the different types of Soil Testing for Construction
√ Gravity Test
√ Moisture Test
√ Atterberg’s Limits Test
• Liquid Limit
• Plastic Limit
• Shrinkage Limit
√ Dry Density Test
• Core Cutter Method
• Sand Replacement Method
√ Proctor’s Compaction Test
Factors to consider when conducting soil testing
Muya explains that the wide range of geotechnical studies available for soil requires professionals to rely on specific guiding factors when determining which tests to conduct. These include: –
The type & importance of the project one intends to undertake. For example, undertaking soil analysis for purposes of mining is will be different from the analysis of soil where one is to carry out an agricultural project or a construction etc.
The costs for undertaking the analysis. This is basically due to the financial envelope allocated to the project.
Soil Characteristics and Structural Considerations
General classification of soil based on sieve analysis preliminary tests or sample observation (type of soil/rock,), variation of soil properties/ geological formation in the land on which structure is to be constructed.
>Selection of type of foundation (shallow / deep, raft etc.) for a construction project
Depth of compressible layer and its thickness.
Effect of ground water table variation.
Modifications/ improvements in existing soil properties are proposed or not.
Variations in factors which will affect bearing /strength properties and settlement/ deformation of the soil.
Balancing Cost, Standards, and Technical Requirements
Although the factors mentioned above complicate decisions on the number of laboratory and field tests to perform, professionals must also consider the cost of geotechnical investigations, the availability of testing facilities, and existing data and experience from similar soil conditions. In addition, applicable construction codes and standards provide clear guidelines on the appropriate number of tests required. However, revisions in codes or standards under development will be of great help since they will consider research experiences in geotechnical investigations, the effect of change in soil conditions and the performance of existing structures.
Additional Practical Considerations in Soil Testing
Adede add’s that other soil testing factors to consider include:-
Location of the project
Nature of the proposed development
Design of the proposed development i. e, depth, size, length, weight, volume etc
Why Soil Testing is Critical for Construction Projects
All construction projects are made on the soil. The soil has to take the weight of the structures. Soil testing provides important clues about the soil’s bearing capacity, density, compaction, presence of organic matter, sand, and contaminants. Sometimes the existing soil needs to be removed because it is contaminated. This could be harmful to habitat.
Managing Soil Contamination and Environmental Risks
For instance, old gas stations often have deteriorating underground gasoline tanks. The gasoline leaks out and contaminates the soil and groundwater over time. In these cases, careful removal and disposal of contaminated soils is necessary. Regulatory bodies such as the EPA and local authorities oversee this process to ensure compliance with environmental and construction standards.
In many cases, engineers remove organic material and replace it with a more stable inorganic substitute, such as gravel. Once they install suitable load-bearing soil, they can proceed with constructing the foundation.
