The mitigation of seismic soil liquefaction in sand with fine content presents a challenge, demanding efficient strategies. This research explores the efficacy of Microbial-Induced Partial Saturation (MIPS) as a biogeotechnical technique to improve the liquefaction resistance of sandy soils with plastic fines. By leveraging the natural metabolic processes of indigenous microorganisms, this method introduces biogenic gas production within the soil matrix, effectively reducing its degree of saturation. This partial desaturation alters the soil's response to cyclic loading, aiming to mitigate the risk of liquefaction under dynamic loading conditions. Experimental results from a series of undrained strain-controlled cyclic shear tests reveal that even a modest reduction in saturation significantly enhances the soil's stability against seismic-induced liquefaction. The investigation extends to analyzing the effectiveness of the MIPS treatment in sands with low-plasticity clay content, offering insights into the interaction between microbial activity, soil texture, and liquefaction potential. Results show that while plasticity plays a key role in improving the cyclic response of soils, the influence of MIPS treatment remains noteworthy, even in sand with plastic fines. Additionally, a modified predictive formulation is introduced, incorporating a calibrated parameter to account for the influence of fines' plasticity on excess pore pressure generation.

Soil liquefaction caused by earthquakes is a devastating occurrence that can compromise the foundations of buildings and other structures, leading to considerable economic losses. Among the new remedies against liquefaction, Induced Partial Saturation (IPS) is regarded as one of the most promising technologies. In order to improve liquefaction resistance and the fluid phase's compressibility, gas or air bubbles are introduced into the pore water of sandy soils. This article deals with the general laboratory evaluation of a sand under partially saturated conditions and under cyclic loading to assess if this technology is applicable for a ground improvement of the examined soil. The use of the Axis Translation Technique for sample desaturation and diffusion-stable butyl membranes significantly influences the laboratory results. Additionally, it is found that the trapped air bubbles of the partially saturated samples act like a damping mechanism, which are reflected in the stress paths of the deviator stress q over the mean pressure p with an inclination of 1 : 3. Zum Verfl & uuml;ssigungsverhalten von teilges & auml;ttigtem SandDie durch Erdbeben verursachte Bodenverfl & uuml;ssigung ist ein verheerendes Ereignis, das die Fundamente von Geb & auml;uden und anderen Bauwerken gef & auml;hrden und zu erheblichen wirtschaftlichen Verlusten f & uuml;hren kann. Die induzierte partielle S & auml;ttigung (Induced Partial Saturation, IPS) gilt als eine der vielversprechendsten Technologien unter den neuartigen Baugrundverbesserungen gegen Verfl & uuml;ssigung. Um den Verfl & uuml;ssigungswiderstand und die Kompressibilit & auml;t der fl & uuml;ssigen Phase zu verbessern, werden dabei Gas- oder Luftblasen in das Porenwasser sandiger B & ouml;den eingebracht. Dieser Beitrag besch & auml;ftigt sich mit der generellen labortechnischen Evaluierung eines Sandes unter teilges & auml;ttigten Verh & auml;ltnissen und unter zyklischer Beanspruchung zur Beurteilung, inwiefern sich diese Baugrundverbesserung f & uuml;r den untersuchten Boden eignet. Die Verwendung der Axis Translation Technique zur Probenentw & auml;sserung und die Verwendung von diffusionsstabilen Butylmembranen haben einen erheblichen Einfluss auf die Laborergebnisse. Au ss erdem ist festzustellen, dass die eingeschlossenen Luftblasen der teilges & auml;ttigten Proben wie eine D & auml;mpfung wirken und sich in den Spannungspfaden der Deviatorspannung q & uuml;ber dem mittleren Druck p mit einer Neigung 1 : 3 widerspiegeln.

Liquefaction, a significant hazard triggered by earthquakes, is characterized by a sudden loss of shear strength due to a rise in pore pressure and the corresponding reduction in effective stresses, leading to structural damage and substantial economic losses. Numerous studies have investigated various mitigation measures for liquefaction. Recently, the focus has shifted toward developing environmentally friendly, cost-effective technologies to enhance liquefaction resistance. One such promising technique is induced partial saturation (IPS), which has the potential to serve as a cost-effective, environmentally friendly, and practical solution for both new and existing structures. The IPS mechanism was examined and discussed extensively in the first part of this review. The effectiveness and usability of this approach in the soil are reviewed in the next section, using small, large-scale laboratory and field-scale testing. Following that, microbubble and pore-scale studies are used to quantify durability and stability. The review has provided several key recommendations to address the current challenges and limitations of the technique, aiming to enhance its effectiveness and stability. Given the ongoing research and the need to ascertain their suitability for practical applications, the existence of a comprehensive literature review becomes essential. This review will provide researchers with valuable insights into the current state of knowledge in this field and serve as a foundation for future studies.

Liquefaction is a common concern for geotechnical engineers in moderate-to-high seismic areas. Loose, non-plastic and saturated soils are most prone to liquefaction. Traditional approaches to decrease liquefaction are still widely used, however there are still major difficulties including restrictions on treatment area size, potential damage to sensitive structures, and environmental impact. Modern methods for liquefaction reduction include passive site remediation, microbial geotechnology and induced partial saturation. Air is far more compressible than water, hence unsaturation or partial saturation can help a soil deposit resist liquefaction. Even small volumes of gas bubbles in saturated soils can increase liquefaction resistance, especially around structures. Recently, bio-denitrification has been used to dissimulate nitrate to nitrogen gas as an alternative desaturation method. In this review article, Induced Partial Saturation (IPS), a modern liquefaction mitigation approach, and its methods: a) Microbially induced partial saturation (MIPS) or biogas and b) Air injection has been discussed in detail. This article examines how compositional and environmental elements affect soil gas bubble retention and treatment system efficiency. Overburden stress, soil density and fines concentration affect gas bubble retention and treatment efficiency. Gas loss from the soil surface, possibly from capillary invasion and crack opening, reduces treatment efficiency.

The microbial induced partial saturation (MIPS) technique is the new environmentally friendly, cost-effective technique applicable under existing structures for mitigating sand liquefaction. The current study investigated the effectiveness of MIPS for mitigating sand liquefaction under undrained static loading. A series of undrained static triaxial tests were conducted to examine the influence of biogenic gas production through microbial denitrification on poorly graded sand at various relative densities. Initial batch experiments revealed that increased nitrate concentrations resulted in a decreased degree of saturation. Loosely and medium-dense saturated samples exhibited positive pore pressure during loading, which was reduced through biological desaturation, resulting in increased undrained shear strength ratios. Dense saturated and desaturated samples produced negative excess pore pressure, decreasing the undrained strength of treated samples due to dilative behavior. The undrained stress-strain behavior of loose and medium-dense sand transitioned from strain softening to strain hardening as the degree of saturation decreased from 100 to 90%. However, dense sand exhibited strain-hardening behavior with decreased saturation from 100 to 95%. Decreasing saturation levels reduced instability susceptibility, resulting in more stable soil behavior and decreasing the potential for large strains and instability. The study demonstrated a reduction in the Liquefaction Potential Index (LPI) for both loose and medium-dense sand as the degree of saturation decreased from 100 to 90%. These findings highlight the potential of MIPS as an effective technique for mitigating sand liquefaction and offer insights into its underlying mechanisms.

Earthquake-induced soil liquefaction is a catastrophic phenomenon that can damage existing building foundations and other structures, resulting in significant economic losses. Traditional mitigation techniques against liquefaction present critical aspects, such as high construction costs, impact on surrounding infrastructure and effects on the surrounding environment. Therefore, research is ongoing in order to develop new approaches and technologies suitable to mitigate liquefaction risk. Among the innovative countermeasures against liquefaction, Induced Partial Saturation (IPS) is considered one of the most promising technologies. It consists of introducing gas/air bubbles into the pore water of sandy soils in order to increase the compressibility of the fluid phase and then enhance liquefaction resistance. IPS is economical, eco-friendly and suitable for urbanised areas, where the need to reduce the risk of liquefaction must be addressed, taking into account the integrity of existing buildings. However, IPS is still far from being a routine technology since more aspects should be better understood. The main aim of this review is to raise some important questions and encourage further research and discussions on this topic. The review first analyses and discusses the effects of air/gas bubbles on the cyclic behaviour of sandy soils, focusing on the soil volume element scale and then extending the considerations to the real scale. The use of useful design charts is also described. Moreover, a will be devoted to the effect of IPS under shallow foundations. The readers will fully understand the research trend of IPS liquefaction mitigation and will be encouraged to further explore new practical aspects to overcome the application difficulties and contribute to spreading the use of this technology.