Soil investigation: a prerequisite for successful foundation repair

To achieve the best possible result, in addition to a thorough understanding of the foundation structure, information about the nature and composition of the subsoil is also of great importance. URETEK therefore welcomes building plans and the results of soil investigations. This enables us to determine the most suitable repair procedure.

Soil investigation reports for foundation repair

There are various techniques for investigating the mechanical properties of the subsoil. A distinction is made between the so-called ‘static penetrometer test’ and the ‘dynamic penetrometer test’.
‘Static’ means that the probe (a metal tube with a tip of standardised dimensions) is hydraulically driven into the ground at a constant speed. The resistance encountered is measured and plotted on a graph, known as the penetration curve. The dynamic test is used for harder soils.
In this test, the probe is driven into the ground using a defined weight and drop height. The number of blows per 10 cm of depth is counted and also plotted on a graph, known as the blow probe curve.

An example of a sounding curve for soil injection

These tests provide definitive information about the mechanical properties of the subsoil. To gain a good understanding of the nature of the subsoil (sand, clay, peat, etc.), the moisture content and the level of the water table, soil borings are necessary. These are used to extract soil samples. A specialist laboratory then analyses the samples and determines the nature and moisture content of the soil. For URETEK, the availability of soil reports is often a prerequisite for accepting a ground improvement contract. When it comes to soil investigation, we often collaborate with reputable geomechanical engineering firms to rule out any risks. Whilst our method is highly cost-effective, this is not the case in every situation. Our method also has its limitations.

Requirements for soil investigation

A geotechnical soil investigation provides insight into the structure of the soil layers. The soil investigation report must contain at least the following information:
– soil probing (minimum depth 10 metres) with cone resistance and friction coefficient
– borehole data (depth of at least 4 metres)
– groundwater level.
It is recommended that a sounding be carried out at at least two different locations. This allows for a better understanding of possible differences in the composition of the soil layers.