# Diatomaceous Soils and Advances in Geotechnical Engineering--Part I
The high diatom content compared to other deposits may be explained by the high friction angle, void ratio, and compressibility coefficient. The analysis of the settlements via secondary consolidation is indispensable in designing geotechnical structures supported on lacustrine deposits containing diatoms [9]. The documented buildings have recorded high values for the compression index (Cc), recompression index (Cs), and void ratio. Therefore, the expected number of settlements is high. The settlement criteria include the factors that govern the determination of the available bearing capacity in the compressible soils of Bogota [9]. On the other hand, Ref. [10] studied the diatomaceous deposit of Klamath County, Bonanza, Oregon (USA), which is located in the zone of influence of the bridge replacement project known as \"OR140 Buck Creek Bridge\". The diatomaceous materials were characterized via field (SPT and CPT) and laboratory tests. The profile indicated that the diatomaceous soil was about 4 m below the surface, and a thickness of 1 m was recorded. Oedometric testing of the \"Buck Creek\" soil indicated high overconsolidation ratios ranging from 10 to 40. These soils exhibited an unusually high shear strength due to \"interlocking\" phenomena between the grains, which exhibited considerable irregularity in their shape. In the project, an unexpected rebound phenomenon occurred during the driving of piles designed with a closed toe. This rejection occurred at depths of less than 5 m.  
Consequently, the construction process had to be modified to open-toe pile driving. The piezometric data indicated that negative pore pressures were generated during the rebound of the closed-toe piles. In situ testing indicated changes in material stiffness and dilatant tendencies near the refusal depth. Dissipation tests conducted near that point indicate a positive induced pore pressure, equivalent to 100 times the hydrostatic pressure,which dissipates rapidly (in less than one h), implying a high hydraulic conductivity. The latter is a phenomenon contradictory to the negative pore pressures mentioned above, which is why [5] insists on the need for further research. The criteria for pile rebound in DS differ from those previously reported in the literature. The authors state that their study is perhaps the first documented case of negative pore pressures being generated during pile rejection. Another case refers to the Cooper Marl sector (Charleston, SC, USA), where rejections have also been recorded in the installation of piles, and whose soils share characteristics with DS in terms of engineering and physical properties. In this area, considerable pore pressures have been observed during pile driving. Rejection has been reported especially in large-diameter piles. This situation is generally managed in practice by alternate installation--i.e., when the rebound of one pile is recorded, proceed with the next one and when it reaches rejection, return to the initial one [5]. Ref. [11] provides the results of the characterization of Bogota soils, which are classified as very soft with a high diatom content, similar to those of Mexico City and the Sea of Japan. At depths greater than 10 m, extreme values have been obtained for some geotechnical properties, such as an LL of 400%, moisture content of 200%, void ratio close to 5, and compressibility coefficient of approximately 5. The usual geotechnical correlations and requirements for the design of foundations need to be revised for soils that present diatomaceous particles in concentrations higher than 40% by weight. From this magnitude, some soils register considerable increases in the liquid limit (LL) and the void ratio, particularly at low stress levels of 12.5 kPa to 100 kPa [12]. The properties of fine soils (silts and clays) are mainly defined by their behavior and not necessarily by their particle size [13].