Geotechnical Engineering Properties Research Articles

Comprehensive Review of Geotechnical Engineering Properties of Recycled Polyethylene Terephthalate Fibers and Strips for Soil Stabilization.

The waste management of plastic has become a pressing environmental issue, with polyethylene terephthalate (PET) being one of the major contributors. To address this challenge, the utilization of recycled PET fibers and strips in geotechnical engineering applications for soil stabilization has gained considerable attention. This review aims to provide a comprehensive study of the geotechnical engineering properties of recycled-PET-reinforced soils. The review examines various factors influencing the performance of PET-reinforced soils, including PET percent content, fiber length, and aspect ratio. It evaluates the mechanical properties, like shear strength, compressibility, bearing capacity, hydraulic behavior, and durability of recycled-PET-reinforced soils. The findings reveal PET reinforcement enhances shear strength, reduces settlement, and increases the bearing capacity and stability of the soil. However, it is observed that the incorporation of recycled PET fibers and strips does not lead to a significant impact on the dry density of the soil. Finally, an environmental and cost comparison analysis of recycled PET fibers and strips was conducted. This review serves as a valuable resource for researchers, engineers, and practitioners involved in the field, offering insights into the geotechnical properties of PET-reinforced soils and outlining future research directions to maximize their effectiveness and sustainability.

Physical, Chemical and Compaction Characteristics of Slightly Weathered Tephras of New Zealand

AbstractThe North Island of New Zealand is a region of high volcanic activity, with significant eruptions over the past. Analogous to past events, future volcanic eruptions would produce a considerable volume of ash and granular soils, covering widespread areas and raising concerns for their disposal and storage. Such deposits, primarily airfall tephra, could be potentially used in geotechnical engineering applications such as foundations, roadway embankments and land reclamations. However, before their use as structural fills can be recommended, detailed laboratory investigations of their physical, chemical, compaction, and geotechnical engineering properties (strength, compressibility, collapsibility, liquefaction potential, etc.) must be conducted. Different tephra deposits can be products of different eruptions, so chemical composition analyses can be combined with the physical, compaction, and engineering properties to characterize such deposits. Accordingly, this paper provides useful insights from physical (grain size, specific gravity, and morphology), chemical (elemental and mineralogy using X-ray fluorescence and X-ray diffraction), and compaction tests (maximum dry density, optimum water content, and particle breakage) for eleven selected volcanic tephra samples sourced from the North Island of New Zealand in the Rotorua, Taupo, and Auckland regions.

Effect of collated fly ash, GGBS and silica fume on index and engineering properties of expansive clays as a sustainable landfill liner

The effect of supplementary cementitious materials (SCMs) such as fly ash (FA), GGBS and silica fume (SF) on the geotechnical index and engineering properties of expansive clays (EC) are studied in this research work. This manuscript aims to determine the workability (consistency limits (CL)), swellability (free swell index (FSI)), compaction properties, strength characteristics (UCS) and hydraulic conductivity (HC) of varied eighteen mix proportions of FA-EC (P-series), FA-GGBS-EC (Q-series) and FA-GGBS-SF-EC (R-series) are experimentally studied as a bottom liner in landfills. From the test results, CL and FSI significantly decreased in P, Q and R series, this is due to the effect of flocculation, a process that increases the average particle size of mix blends and also depletion of the double-diffusive layer thickness of EC by promoting the Ca2+ ions in the pore water from SCMs. The compaction parameters such as optimum moisture content decreased in all the series, due to the higher flocculation of mixes. However, maximum dry unit weight increased in Q and R and decreased in the P series. The UCS values increased with an increase in optimum SCMs quantities and with curing intervals tested at 0, 7, 14 and 28 days. The higher UCS value is attained at 40 %FA with EC (i.e. P2), 60 %FA-GGBS with EC (i.e. Q3) and 60 %FA-GGBS-SF with EC (i.e. R3) in R-series which confirmed to be optimum due to the loss of cementation action/reduced cohesion in the matrix. In the case of HC, P2, Q3 and R3 mixes are confirmed to be optimum and fall under the criterion standards of landfill liner as per USEPA recommendation. Overall, this work proves to be a novelty and shows the feasibility of various collated SCMs blended with EC as landfill liner material, furthermore, these mixes are optimized to combine with EC to create a sustainable landfill liner that fits with the United Nations sustainable goals of 2030

Study on mechanical properties and microstructure of fly-ash-based geopolymer for solidifying waste mud

The chemical solidification of construction waste mud presents a strategy for mitigating environmental concerns as well as addressing problematic geotechnical engineering properties. The present study explores the efficacy of utilizing fly ash (FA)-based geopolymer, activated by calcium carbide residue (CCR) and sodium silicate solution (NS), for waste mud solidification. An unconfined compressive strength (UCS) test was conducted to ascertain the optimal CCR/NS ratio. Supplementary tests were executed to examine factors such as water content, pH level, X-ray diffractometry (XRD), scanning electron microscopy (SEM), and natural dehydration. According to the UCS results, an optimal 28-day strength of 2.2 MPa was observed when employing a CCR/NS ratio of 6:4. A notable reduction in the water content of the mud was achieved in the short term, with the most effective results observed at a pH level of 12. Microstructural analyses indicated that calcium silicate hydrate (CSH) and aluminosilicate-Na hydrate (NASH) acted as the primary cementitious products, filling pores and creating bonds with particles to facilitate strength development. Variations in crack morphology and water content during the natural dehydration process were also analyzed for both solidified and untreated mud. The findings suggest that solidified mud holds promise for application in subgrade engineering projects, potentially diverting significant volumes of waste mud and industrial by-products such as CCR and FA away from landfills.

Investigation of Mechanical and Physical Features of Cementitious Jet Grout Applications for Various Soil Types

The cementitious jet grout method (CJG) is one of the most preferred methods for the ground reinforcement of building foundations. As a result of the soil improvement made with the CJG, it was observed that there was a decrease in settlement, permeability, and liquefaction potential and an increase in the bearing capacity. In this study, columns with different grouting pressures (400, 450, and 500 bar) and water/cement ratios of 0.75, 1.00, and 1.25 were produced on several soil types (sand, clay, and alluvial soil) that have high liquefaction, settlement potential, and low bearing capacity. CJG columns were kept for 28 days after completion and then removed from the soil, and diameter measurements were made and significant differences were observed according to pressure and w/c ratios. Three samples were taken in CJG columns extracted from the ground. Laboratory tests were conducted to determine the physical (water absorption rate, density, and porosity) and mechanical (UCS and UPV) properties of CJG column samples. The highlighting of this paper is to build full-scale CJG columns in sandy soil, clay soil, and alluvial soil, increase the geotechnical engineering properties, and investigate the strength development, and diameter under different w/c ratios and different injection pressures. The strength of CJG columns in sandy soils was found between 36 and 15 MPa, in clay soils between 15 and 4 MPa and in alluvial soils between 32 and 15 MPa. Moreover, it was observed that there was a significant increase in the diameters with the increase in the injection pressure and a decrease in the compressive strengths. When the CJG column diameters were compared with constant injection pressure and increasing w/c ratios, the maximum increase was found to be 13% for sandy soils, 10% for clayey soils, and 14% for alluvial soils. The column diameters were 37% larger for sandy soils than clayey soils and 26% larger than alluvial soils at the same w/c ratio and constant injection pressure. In conclusion, since the results found in this study were made on a real scale in the field and for three different soil conditions, the results can be used directly in future engineering applications.

Experimental study on bio-treatment effect of the dredged Yellow River silt based on soybean urease induced calcium carbonate precipitation

As the river with highest silt content in the world, the Yellow River is dredged annually to relieve the pressure of flood control. Prior studies indicated that the dredged Yellow River silt cannot be directly utilized as construction filling material because of the deficiency in strength and stability. In this study, soybean urease induced calcium carbonate precipitation (SICP) method was proposed to solidify the Yellow River silt for the purpose of promoting its mechanical properties. The influences of soybean powder concentration and pH value on the soybean urease activity were investigated. By estimating the urease activity of per unit mass, the soybean powder concentration with highest extraction efficiency were determined. The optimum bio-treatment recipe including cement solution concentration and grouting time of the biological solidification agent suitable for the Yellow River silt was characterized through unconfined compressive strength (UCS) test and CaCO3 content test. Meanwhile, scanning electron microscope (SEM) and X-ray diffraction (XRD) analysis of the bio-treated Yellow River silt sample verified the effectiveness of solidification from microscopic viewpoint. The findings of this study suggest that soybean urease induced calcium carbonate precipitation (SICP) method can effectively improve the geotechnical engineering properties of Yellow River silt and provide a technical approach for the resource utilization of the Yellow River silt.

Effect of Crude Oil on the Geotechnical Properties of Various Soils and the Developed Remediation Methods

Crude oil still affects many countries because it is one of the essential fuel sources. It makes life more manageable in modern communities and cannot be overstated because it is easy to use and find. However, the pollution caused by its use in industries such as mining, transportation, and the oil and gas business, especially soil pollution, cannot be ignored. Soil pollution is an issue in most communities because it influences people and ecology. Accidental infusions and spills of ore oils are prevalent occurrences leading to the entire or fractional exchange of the soil pore fluid by oil-contaminated soils that have affected the geotechnical engineering properties. The liquid limitations for polluted soil grades silty loam and sandy loam decreased by 38% and 16%. Oil contamination leads to decreased permeability; the permeability values for sandy loam soil decreased from (3.6 × 10−6 to 0.25 × 10−6 cm/s) when the oil content increased from 0 to 16%; however, the permeability values for silty loam decreased from (2.6 × 10−6 to 0.25 × 10−6) cm. The current study results exhibit that the geotechnical properties of contaminated soil with oil slag can be modified upon adding cement at different weight percentages (3, 5, and 7%) to the soil. The Atterberg limits and specific gravity of the soil were noticeably reduced when it was stabilised with cement, as well as because oil spills on soil significantly influence the environment. So, there is an immediate and critical need for efficiently removing petroleum hydrocarbon pollutants from contaminated soil. Bioremediation is a new technology gaining interest worldwide to clean up sites that have polluted petroleum hydrocarbons.

Accelerated Reinforcement of Calcareous sand via Biomineralization with Aluminum Ion Flocculant.

Microbially induced calcium carbonate precipitation (MICP) is an immensely growing technique that utilizes the metabolic pathways of bacteria to form calcite precipitation throughout the soil matrix, leading to improve geotechnical engineering properties. However, the excessive number of treatments limited the application of MICP for strengthening calcareous sand. To reduce the number of treatments and develop efficiencies, this paper investigates the optimized treatment protocol of adding aluminum ion flocculants to the cementing solution to accelerate the curing rate of the MICP and its effect. The results show that adding a certain concentration of AlCl3 to the cementing solution can resulted in a rapid increase in strength of the calcareous sand column. When 0.02M aluminum chloride was added to the cementing solution, the unconfined compressive strength of the sand column reached 827kPa after three treatments, and it reached 2MPa after five treatments, while the control group needed to be treated 10 and 15 times, respectively, to reach equivalent strengths. In this paper, the unconfined compressive strength of the sand column formed using the proposed method was 27-40 times that of the control group at the same calcium carbonate content. The presented experimental approach can be used as a tool to design the treatment protocol for the engineering application of MICP-reinforced calcareous sand in practice.

Using water treatment sludge to Improve Geotechnical Engineering Properties of Soils: A Review

Water treatment sludge (WTS) is a byproduct generated during the treatment of wastewater. In recent years, researchers have explored the potential of using WTS as a soil stabilizer to improve the geotechnical properties of soils. In this review, we will examine the current state of knowledge on the use of WTS for this purpose. The organic matter content of WTS is usually high and can range from 30% to 60%. The high organic matter content makes WTS a potential source of nutrients for plants, and it can also enhance soil structure and water retention. Another important consideration is the environmental impact of using WTS. The use of WTS can be an eco-friendly alternative to chemical stabilizers, which can have adverse effects on the environment. However, there are concerns about the potential for heavy metal contamination in WTS. To mitigate this risk, it is recommended to conduct thorough testing of WTS before using it as a soil stabilizer. Finally, the use of WTS as a soil stabilizer has the potential to improve the geotechnical properties of soils. However, it is essential to consider factors such as the type and dosage of WTS, the soil type, and the environmental impact before using it. Further research is also needed to explore the potential of using WTS in different soil types and environmental conditions.

Engineering Structural Strength Properties of Lateritic Soil-Cement Mix for Road Pavement Stability

Qualitative construction materials in highway pavement prompted addition of cement at different proportion of 2 - 10% to lateritic soils for enhanced performance. Engineering geological tests were performed on the soil-cement mixture to determine their highway pavement suitability for durable road construction. Furthermore, modelling of the strength characteristics of the mixture presents the correlation between the structural properties and cement mix. Thus, increase in soil-cement California bearing ratio (CBR) and unconfined compressive strength (UCS) values with higher cement mix of 8%, revealed enhanced soil improvement. The soil strength is also affected by the curing period. Better quality strength characteristics obtained decreases pavement thickness with reduced cost in road construction. Relationship between the soil strength properties and cement mix content are represented by polynomial model. This reveals stronger bearing capacity of soil cement mix cured in 14 days with R2 ≥ 0.8. The lateritic soil cement mix at 8% cement content could serve as highway subbase and base construction materials. Cement mix having positive effects on soil geotechnical properties are indication of its effectiveness in enhancing volume stability of different soils. Prolong curing time is essential for compacted soil cement mix for enhanced geotechnical engineering properties and to improve the quality of lateritic soil used as road construction materials. Thus, cement-stabilized lateritic soil reduces cost of road construction, its persistent failure, human and environmental losses.

Effect of cockle shell powder as sustainable additive on geotechnical engineering properties of stabilized soil

Effect of cockle shell powder as sustainable additive on geotechnical engineering properties of stabilized soil

Improvement of Geo-engineering Properties of Expansive Clayey Soil by using Sodium Chloride and Bagasse Ash

Expansive soils contain minerals such as smectite clays that are capable of absorbing water accompanied by shrink and swell behavior and thus change in volume. The swell–shrink behavior of these soils could lead to instability of the structures found on them, specifically the light-weight structures and pavements. Expansive clay soil is encountered in most parts of Egypt. A comprehensive study was made in Sixth of October city to investigate the impact of lime sludge and bagasse ash as an industrial solid waste from sugar-cane factory and sodium chloride salt on geotechnical engineering properties of expansive soil. The macrostructural properties are quantified through laboratory testing for Free swell index, Plasticity index and infiltration tests. The microstructural aspects of the treated soil are observed through X-ray diffraction studies and SEM micrographs. The laboratory results showed that by increasing the lime sludge, Bagasse ash and NaCl concentrations the liquid limit decreased from 100% to 60% while the plastic limit increased from 100% to 90% respectively. In addition, the infiltration tests showed an increase in the infiltration rate from 10% to 80% when LS and Bagasse ash were added to the soil also the free swell decreased from 100% to 70 % sufficiently. XRD patterns showed the formation of new kaolin cementitious compound as the change of montmorillonite to kaolinite mineral took place due to the reaction of high amount of calcium ions produced from the stabilizer, the cation exchange took place between the calcium cation of the lime associated with the surfaces of the clay particles. The effect of cation exchange and attraction causes clay particles to became close to each other, this process is called flocculation which is accompanied by a series of pozzolanic reactions resulting in the formation of clay aggregates that are bound together by the new cementitious products such as calcium aluminate. Scanning Electron Microscopic images (SEM) and SEM micrographs determined the formation of organized dense clay matrices of aggregations that showed the reduction of Montmorillonite clay mineral peak intensities and an increase in kaolinite clay mineral peak intensities due to the change of expansive soil texture and reduction of interplanar spacing of the treated soil.

Geotechnical Engineering Properties of Cement Fly Ash Gravel Mixtures for Application as Column-Supported Highway and Railway Embankments.

Our study investigates the geotechnical engineering properties of cement fly ash gravel mixtures in the laboratory. Gravels with three different size ranges were blended with cement and fly ash. The mixture properties were investigated, including the porosity, density, permeability, unconfined compressive and splitting tensile strengths, cohesion, and friction angle after curing for 28, 50, and 90 days, respectively. The experimental results revealed that the gravel sizes and fly ash contents significantly influenced the strength characteristics. The permeability coefficients of the cement fly ash gravel mixtures were 0.9 to 1.7 cm/s, much higher than a soil-cement column. The unconfined compressive strengths and splitting tensile strengths were found to be from 3.75 to 18.5 MPa and from 0.5 to 2.5 MPa, respectively. The cohesion and friction angle values ranged from 2.2 to 5.3 MPa and 30 to 40 degrees. The mixture strength was 6 to 30 times higher than a soil-cement column. The 15% fly ash provided the best strength characteristics as it exhibited the most significant calcium silicate hydrate contents. Thus, using cement fly ash gravel column-supported embankments is more productive than using a soil-cement column and granular pile to increase the column-bearing capacity and overall stability and accelerate the consolidation process.

Experimental Study on the Strength Characteristics of Expansive Soils Improved by the MICP Method

Microbially induced calcite precipitation (MICP) has been a promising method to improve geotechnical engineering properties; however, there are few literatures about the application of the MICP method to improve the strength characteristics of expansive soils with low permeability. In this paper, a series of CD triaxial tests were carried out to investigate the effect of the MICP method on the strength characteristics of the expansive soils. The results show that the shear strength of the specimens increased with the increase in the cementation solution and eventually reached a stable value. The MICP method can significantly improve the shear strength index of the expansive soils. The cohesion of the expansive soils was increased from 29.52 kPa to 39.41 kPa, and the internal friction angle was increased from 20.13° to 29.58°. The stress-strain curves of expansive soil samples improved by the MICP method show a hyperbolic relationship, which is characterized by strain hardening. The hyperbolic model was chosen to describe the stress-strain relationship of the expansive soils improved by the MICP method, and the predicted results were in good agreement with the measured results. Moreover, we performed a scanning electron microscope (SEM) experiment and revealed the mechanism of the MICP method to improve the strength characteristics of expansive soils. The conclusions above can provide a theoretical basis to further study the strength characteristics of improved expansive soils by the MICP method.

Prediction of Gypseous Soil Settlement Using Artificial Neural Network (ANN)

Gypseous soil exhibits problematic geotechnical engineering properties as they expand, collapse, disperse, undergo excessive settlement, owns a distinct lack of strength, and it is soluble. Gypseous soil has a metastable structure, with dissolvable minerals with a minimal quantity of clay binding the particles together. When gypseous soil unsaturated, they are quite potent. When they are subjected to increased wetness, however, the excess water weakens or damages the bonds, resulting in shear failure and subsequent settlement. Estimating the settlement of shallow foundations on gypseous soils is a difficult topic that is still not fully understood. It is concluded that artificial neural network (ANN) is appeared to be viable solution since it has been successfully used in numerous prognosis applications in geotechnical engineering. In this research, the precipitation values of gypsum soil were predicted under the influence of the applied load using an artificial neural network. The study found that this model is very good in predicting precipitation and found a convergence between the real values and the predict values.

Geotechnical properties of marine dredger fill with different particle size

To get a macroscopic understanding of the geotechnical engineering properties of typical marine dredger fill in coastal areas of Shandong Province, China, the mineral composition, particle size distribution, cation exchange capacity (CEC), consolidation characteristics, and strength characteristics of dredger fill in four regions, namely Rizhao, Dongying, Weifang, and Yantai, were studied and the correlation between typical indicators of dredger fills in different regions were analyzed. The results show that the difference in soil particle size distribution in Shandong province is related to the regional sedimentation type and dynamic effect and there is a significant correlation between some typical soil indicators. Vane shear strength test and consolidation test results show that the silt in Weifang has good drainage and shear strength indicating it is suitable as dredger fill. For the mucky clay in Rizhao, pharmaceutical vacuum preloading method is recommended to improve soil strength and the reasonable loading size should be less than 200 kPa. The purpose of this paper is to study typical geotechnical properties of four types of dredger fill, find and verify the correlation between some of geotechnical properties, to provide an objective scientific reference basis for the treatment of dredger fill in coastal area from the perspective of dredging and filling engineering.

Effect on engineering properties of ground granulated blast furnace slag admixed with laterite soil, cement and bentonite mixtures as a liner in landfill

This paper showcases the geotechnical and environmental engineering properties of ground granulated blast furnace slag (GGBS, a byproduct of iron-ore) admixed with local laterite soil (LS), bentonite (BT) and cement (CT) mixtures as landfill liner. The main aim of this study is to determine the effect of GGBS on LS (i.e. effect of binder material with filler material) and to study the effect of GGBS-LS blended with varied BT and CT mixtures (i.e. binder-filler material in partial replacements), to perpetrate as a landfill liner material. Overall, a wide range of fifteen unique mix proportions was chosen in this study and are categorized into five series. Laboratory tests such as consistency limits, free swell index (FSI), Proctor compaction, hydraulic conductivity (HC), leachate characteristics (LC) and unconfined compressive strength (UCS) with post-testing analysis were conducted to evaluate the optimum mix. From the test results, the consistency limits and FSI decreased with an increase in GGBS content for all the mixes. In compaction tests, the addition of GGBS increases the dry unit weights and reduces the water contents. The HC decreased with the addition of GGBS quantities when permeated with deionized water and diesel oil as permeant fluids. In the LC, the concentrations of heavy metals (i.e. Cr, Co, Cd, Fe and Pb) in diesel oil decreased and removal efficiencies increased for lower HC values than higher HC values. The UCS values increased with an increase in GGBS quantities and curing intervals for all the mixes. The microstructure and mineralogical analysis revealed the identification and confirmation of new cementitious products which ameliorated the UCS values. Hence, from this study, when GGBS admixed with filler and other binder material established to be an efficacious and eco-friendly solution which not only reduces the disposal problem but improves the engineering properties and prerequisite as landfill liner.

Understanding the performance of expansive subgrade materials treated with non-traditional stabilisers: A review

Expansive soils are problematic soils which pose a risk to the safety of civil engineering structures. These soils can be treated by compaction or by adding additives to the soil. Where the strength and properties of expansive soil cannot be improved via mechanical stabilisation (Compaction), a desirable strength can be achieved through the use of chemical admixture techniques. The swelling and shrinkage of expansive soils cause movement in the soil mass resulting in a deferential settlement in engineering structures such as roads and building leading to cracks and subsequent failure leading to high cost of maintenance. Calcium based additives such as cement and lime have been used in expansive subgrade stabilisation to enhance the strength, reduce swell and subsequent differential settlement. However, the growing concerns on carbon dioxide (CO2) emission and climate change have reignited the need for a more sustainable soil stabilisation techniques using waste materials. In this study, non-traditional expansive subgrade treatment techniques using sustainable waste materials with respect to their efficiency in improving the geotechnical engineering properties of the subgrade materials have been investigated and reviewed. This study also discusses the engineering problems associated with expansive soils, proposing an effective, efficient, cheaper and sustainable application of non-traditional stabilisers in expansive soil stabilisation. The study concludes that, the addition of non-traditional stabilisers in expansive subgrade stabilisation using chemical stabilisation techniques can improve the engineering properties of expansive subgrade materials.

Site application of biopolymer-based soil treatment (BPST) for slope surface protection: in-situ wet-spraying method and strengthening effect verification

Recently, environmentally friendly biological soil treatment approaches have been proposed to enhance the geotechnical engineering properties of soils. Biopolymer-based soil treatment (BPST) has been verified by extensive laboratory-scale studies as an effective ground improvement method and suggested as a new reinforcing approach for levee slope owing to its soil strengthening and vegetation promotion. However, the BPST performance and governing factors in field applications have not been thoroughly understood owing to the lack of field-scale research. In this study, a BPST field application was conducted using a wet-type soil spraying method. Biopolymer binders and site soil were mixed and sprayed for slope surface protection following the general procedure of seed spraying. The in-situ application performance and effects of implementation factors such as biopolymer phase (dried powder and prehydrated solution), prior mixing time before spraying and residue mixing time during spraying, and biopolymer recipes were assessed by comparing the unconfined compressive strengths of in-situ samples collected during site spraying and uniformly mixed samples prepared in the laboratory. The solution form of the biopolymer was advantageous for a better quality (similar to the laboratory-scale performance with uniformity) when it was priorly mixed for at least 20 min at a mixing volume of 1 m3. The field-scale implementation and quality analysis of the biopolymer-based binder in this study can contribute to narrowing the gap between field and laboratory performances and qualities.

Geotechnical Engineering Properties of Soils Solidified by Microbially Induced CaCO3 Precipitation (MICP)

Microbially induced calcium carbonate precipitation (MICP) uses the metabolic function of microbes to carry out biochemical reactions with other substances in the environment. Through the controlled growth of inorganic minerals, soil particles are cemented and soil pores are filled to solidify the soil and reduce its permeability. Thus, the application of this technology was foreseen in geotechnical engineering and environment (building antiseepage, contaminated soil restoration, slope soil erosion, and sand liquefaction). In this review article, based on current research findings, the urea hydrolysis and the cementation mechanism of MICP are briefly described. The influences of factors such as enzyme activity, cementation solution concentration, pH, temperature, grouting method, and particle size on MICP-treated soil are discussed. The engineering properties of MICP-treated soils are evaluated, for instance, the strength, stiffness, liquefaction resistance, permeability, and durability. The applications of MICP technology in ground improvement, geotechnical seepage control, foundation erosion resistance, and fixation of heavy metals are summarized. Finally, future directions of the development of MICP technology are elucidated to provide a reference and guidance for the promotion of MICP technology in the geotechnical engineering field.