Deficient Geotechnical Project Support for Middle Eastern Residential Development Projects

Of late, it has become progressively apparent that there is a general perception of the granular desert soils which prevail throughout the Arabian Peninsula frequently being expected to provide characteristically good bearing capacity and low settlement potential. As such, the dominant soil types are somewhat routinely regarded as offering a reliable foundation medium. A consequence of this school of thought is that geotechnical exploratory work for low rise general development projects may well be minimalist, rudimentary, or not infrequently both.

Whilst a substantially homogeneous continuum of relatively compact and well graded granular soils would typically be expected to provide reasonable foundation conditions adequate for modest loading conditions, such a wide-ranging presumption cannot be relied upon within arid environments. Arid soils are frequently characterised by factors that are derived from their having been subject to prevailing moisture deficit conditioning and which directly influence their engineering performance. Of particular significance are:

  • Unsaturated Soils: Surface desiccation with underlying soils having a low moisture content where the groundwater level remains at a low level;
  • Aeolian Origins: Many arid soils have been transported and deposited by wind, from which poor (substantially uniform) grading characteristics are typical and very loose or loose in situ conditions prevail;
  • Permeability: Susceptibility to groundwater movement is enhanced by poor grading and looseness of state;
  • Soil Chemistry: Soils with a high content of salts, mainly sulphates and chlorides which are largely soluble, coupled with saline groundwater conditions;
  • Cementation: The capillary rise of saline groundwater followed by surface evaporation gives rise to increased surface concentration of soluble salts. This process can lead to the cementing of soils by the precipitation of salts and development of duricrust; and
  • Accelerated Weathering: The rate and depth of bedrock weathering is increased in both arid and tropical environments. In particular, high plasticity clays derived from highly active (moisture susceptible) clay mineral products are frequently derived from the rapid deep weathering of volcanic rocks.

 

Whilst an ultimate bearing capacity failure in granular soils is an unlikely prospect, it is important that designers are aware of the considerable near surface variability of arid ground conditions that can prevail, and of the several adverse consequences of soil disturbance, ground loading or change of groundwater conditions. The undernoted table summarises various circumstances that have been identified by HKA whilst conducting investigation into several instances of building serviceability threshold exceedance through the Middle East:

Without an adequate package of ground exploration planning, procurement, implementation, interpretation and design application being applied at project inception, the ground remains a hazard.”
Dudley English, Geotechnical Advisor & Consultant, Glasgow, HKA

Whilst an ultimate bearing capacity failure in granular soils is an unlikely prospect, it is important that designers are aware of the considerable near surface variability of arid ground conditions that can prevail, and of the several adverse consequences of soil disturbance, ground loading or change of groundwater conditions. Table 1 summarises various circumstances that have been identified by HKA whilst conducting investigation into several instances of building serviceability threshold exceedance through the Middle East:

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