Climate change and global warming have prompted a notable shift towards sustainable geotechnics and construction materials within the geotechnical engineer’s community. Earthen construction materials, in particular, are considered sustainable due to their inherent characteristics of having low embodied and operational energies, fire resistance, and ease of recyclability. Despite these attributes, they have not been part of the mainstream construction due to their susceptibility to water-induced deterioration. Conventional soil improvement techniques are generally expensive, energy-intensive, and environmentally harmful. Recently, biostabilization has emerged as a sustainable alternative that can overcome some of the limitations of existing soil improvement methods. Enzyme-induced carbonate precipitation (EICP) is a particularly promising technique due to its ease of application and compatibility with different soil types. EICP exploits the urease enzyme as a catalyst to promote the hydrolysis of urea inside the pore water, which, in the presence of calcium ions, results in the precipitation of calcium carbonate. The purpose of this paper is to provide a state-of-the-art review of EICP stabilization, highlighting the potential application of this technique to field problems and identifying current research gaps. The paper discusses recent progress, focusing on the most important factors that govern the efficiency of the chemical reactions and the precipitation of a spatially homogenous carbonate phase. The paper also discusses other aspects of EICP stabilization, including the degree of ground improvement, the prediction of the pore structure of the treated soil by numerical simulations, and the remediation of potentially toxic EICP by-products.

For the first time in Pakistan, Steel Fibre-Reinforced Shotcrete (SFRS) is used as the final lining for the Diversion Tunnels of Gulpur Hydropower Project. The project’s diversion tunnels were opened for operation since 2016 and along with the normal operating inflow of the river, over the course of 3 years, have experienced two major floods as well. Due to schedule constraints, conventional-reinforced concrete lining was only used in the invert portion and the side walls up to a height of 1.6 m in both tunnels and for the remaining portion of the tunnels, SFRS was used. The major advantage of SFRS over conventional lining is the reduced construction time compared to when conventional lining is used. Quantity and cost comparisons of both lining methods show that SFRS is almost 25% more costly per meter length of tunnel while more than 40% faster to construct compared to conventional lining. As-built sections show very little reduction in the area of lining which exemplifies SFRS as not only stable but flood resistant as well.

The design of curtain grouting for dams on rock foundations and the importance of finite element seepage analysis is reported by highlighting a case study of the upstream cofferdam of Gulpur Hydropower Project, Pakistan. Results from seepage analysis decreased the scope of curtain grouting by almost 3 times as compared to initial scope based on results from empirical correlations and water pressure tests. The total grouting holes were decreased from 185 to only 66 and this meant a decrease of construction time by 72% and saved a huge amount of capital and resources as well. The performance of the grout curtain is concluded to be satisfactory, for an operation phase of 3 years which includes two major floods as well and during this period, no visible erosion, quick condition or saturation was found on the downstream end. The paper concludes that if the safety criteria are satisfied, even with high inflows of the river, the scope of curtain grouting can be partially reduced or completely eliminated for temporary dams having an operational life of 1–5 years.

Recent research in geomechanics has increasingly focused on developing carbon-efficient construction materials, with raw earth emerging as a promising candidate due to its favourable hygroscopic properties and natural abundance. Despite these advantages, raw earth’s major drawback is its inadequate durability against water erosion and its relatively weak strength compared to concrete or cement/lime-treated raw earth. This paper investigates the durability, mechanical and microstructure properties of a fine silty-clayey raw earth through enzymatically induced carbonate precipitation (EICP) stabilisation, employing soybeans as a cost-effective source of urease enzyme in its crude extract form. With an anticipated calcium carbonate content of 8%, durability tests reveal a significant improvement in the EICP-treated samples compared to untreated ones. Nevertheless, both untreated and treated samples are deemed suitable only for dry applications due to observed cracking in contact tests. Results from triaxial tests indicate a substantial increase in cohesion for the treated samples relative to the untreated samples. Mercury intrusion porosimetry tests illustrate a decrease in large sized pores and an emergence of a single pore family in EICP-stabilised samples. It is concluded that the properties of EICP-treated samples could be further enhanced with a greater calcium carbonate content as well as by using water-repellent coatings.