High Soil Strength Research Articles

Experimental and numerical modeling on vacuum consolidation behavior of staged-filled soil slurry with prefabricated horizontal drain and flocculant

The vacuum-assisted prefabricated horizontal drain offers a promising method for strengthening soil slurry, allowing simultaneous filling and vacuum-dewatering via staged construction. However, there is limited research on the unique characteristics of staged filling. This study aims to investigate the vacuum consolidation process of staged-filled soil slurry through laboratory model tests and numerical simulations, also assessing the impact of anionic polyacrylamide. Comparative analyses are conducted between vacuum consolidation with and without anionic polyacrylamide, as well as self-weight consolidation without anionic polyacrylamide. Results reveal contour lines of excess pore pressure, water content, and soil strength forming an ellipse around the prefabricated horizontal drain board. During the consolidation process, a higher degree of consolidation, lower water content, and higher soil strength were observed closer to the prefabricated horizontal drain board. After treatment, the uppermost filling layer exhibits an average water content that was approximately 40% higher than the lower filling layer, and its average strength was about 60% lower. This discrepancy is primarily due to the absence of sealing on the top surface and the relatively short vacuum consolidation time caused by staged filling. The introduction of anionic polyacrylamide-induced flocculation significantly improves the initial consolidation rate but minimally affects the dewatering capacity of vacuum preloading. Using flocculant can enhance both the staged filling rate and soil strength (by 1–2 times). Additionally, employing a staggered arrangement between different prefabricated horizontal drain layers is advisable to prevent top-down penetration in areas with low soil strength.

Behavior of Cofferdam Using Non-uniform Geotextile Mats on Soft-overlying-stiff Foundation

Non-uniform geotextile mats are employed as soft foundations in cofferdams. However, investigations on the influence of complicated geological conditions on the mechanical behavior of cofferdams are limited. We investigated the behavior of a cofferdam using non-uniform geotextile mats to explore the failure mechanism of non-uniform geotextile mats over a soft overlying stiff foundation and quantify its stability. The two typical failure modes, global and local failure modes, differed distinctly in the velocity field and sliding surface shape. Geometric factors may partially affect the failure mode, whereas a higher soil strength can enhance the stability of the cofferdam, especially when stiff soil is involved. The failure mechanisms of cofferdams using non-uniform geotextile mats on soft overlying stiff clay and a corresponding stability prediction method are proposed to guide the design of cofferdams using non-uniform geotextile mats.

Physical Conditions That Limit Chickpea Root Growth and Emergence in Heavy-Textured Soil

The tillage method determines several soil physical parameters that affect the emergence of post-rice chickpea (Cicer arietinum L.) in the Indo-Gangetic Plain of South Asia. Mechanised row-sowing with minimum soil disturbance and crop residue retention in medium-to-heavy-textured soils will alter the seedbed when compared to that prepared after traditional full tillage and broadcast sowing. Whilst minimum soil disturbance and timely sowing may alleviate the soil water constraint to crop establishment, other soil physical properties such as soil strength, bulk density, and aggregate size may still inhibit seedling emergence and root elongation. This study’s objective was to determine the limitations to chickpea crop establishment with increasing bulk density and soil strength, and different aggregate sizes below and above the seed. In two growth cabinet studies, chickpea seed was sown in clay soil with (i) a bulk density range of 1.3–1.9 Mg m−3 (Experiment 1) and (ii) the combination of bulk densities (1.3 and 1.8 Mg m−3) and aggregate sizes (<2 mm and >4 mm) above and below the seed (Experiment 2). Root length was significantly reduced with increasing bulk density (>1.4 Mg m−3), and soil strength impeded early root growth at >1 MPa. Where main root growth was impeded due to high bulk density and soil strength, a greater proportion of total root growth was associated with the elongation of lateral roots. The present study suggests that the soil above the seed needs to be loosely compacted (<1.3 Mg m−3) for seedling emergence to occur. Further research is needed to determine the size of the soil aggregates, which optimise germination and emergence. We conclude that soil strength values typical of field conditions in the Indo-Gangetic Plain at sowing will impede the root growth of chickpea seedlings. This effect can be minimised by changing tillage operations to produce seedbed conditions that are within the limiting thresholds of bulk density and soil strength.

Estimating Soil Strength Using GIS-Based Maps - A case study in Sweden

Soil strength is an important parameter for planning of forest roads and harvesting operations. Locating roads to areas with high soil strength reduce both build and maintenance costs. Locating logging trails to high strength areas minimise soil disturbances, e.g., rutting and compaction of forest soils. GIS-based maps of soil type and soil moisture can be valuable tools to estimate soil strength. The aim of this study was to evaluate the use of soil moisture map, i.e., depth-to-water (DTW), maps and soil type maps, to estimate soil strength expressed as California bearing ratio (CBR). CBR, volumetric water content, and ground penetration depth were measured in 120 sample points, separated on three soil classes (clay-silt sediments, sand sediments, glacial till) and two soil moisture classes (wet, dry). In each point, soil samples were collected for validation of the soil type maps. There was a high conformance between soil moisture predicted by DTW maps and field measurements, but conformance of the soil type between maps and field estimates varied between soil types. For sediment soils, dry soils were consistently stronger than wet soils. Soil strength of glacial till soils was more complicated with a binary CBR distribution depending on soil stoniness. Glacial till soils possible to penetrate to 20 cm depth with the dynamic cone penetrometer had CBR values close to those for sand sediments. There is a potential to estimate soil strength from DTW and soil type maps, but these variables should preferably be complemented with other data.

К РАСШИРЕНИЮ ЭКСПЛУАТАЦИОННЫХ ХАРАКТЕРИСТИК ЗЕМЛЕРОЙНО-ТРАНСПОРТНЫХ МАШИН

This article presents materials related to the development of a promising dump design for various types of bulldozers used on high-strength soils. The most important parameter of bulldozers is productivity, which depends on the amount of soil moved by the blade in one working cycle, characterized by the volume of the drawing prism. A characteristic sign of overloading of dumps is the slipping of tracks or tractor wheels. This phenomenon significantly affects the reliability of components and parts of bulldozers, reducing their productivity. To eliminate this, rotary dumps can be used, allowing them to be rotated at a certain angle in both directions relative to the longitudinal axis of the machine, but their restructuring is quite time-consuming and not always effective. The analysis of numerous sources made it possible to develop a prom-ising technical solution at the level of inventions, which makes it possible to efficiently perform earthmov-ing operations related to the treatment of high-strength soils. As a result of analytical studies, taking into account the cutting resistance force of 7 kN, the geometric parameters of the gear engagement (gear wheel-rail) were calculated, the engagement module was adopted m = 10 mm. Recommendations are given on the choice of gear wheel and rail material – 45 normalized steel. For angular rotations of the side sections of the blade, it is recommended to use a hydraulic cylinder with a double-sided rod with an internal cylinder diameter of dv = 40 mm and a rod diameter of ds = 20 mm, at a working fluid pressure of p=10 MPa. It is recommended that the blade rods be made of 80x60 Steel 85 pipe, which ensures their stability during the operation of the bulldozer blade.

High soil strength and cereal crop responses to deeper tillage on sandy soils in a semi-arid environment

High soil strength and cereal crop responses to deeper tillage on sandy soils in a semi-arid environment

Dynamic torsional impedance of large-diameter pipe pile for offshore engineering: 3D analytical solution

Wind-induced or current-induced torsional vibration is a long-neglected issue for offshore engineering (e.g., offshore wind turbines, offshore oil platforms, etc.). As the dimension of the pipe pile implemented offshore increases dramatically, the one-dimensional rod theory can no longer precisely compute the dynamic torsional impedance. This paper proposes a novel 3D torsional soil-pile interaction model and derives the corresponding analytical solution for the 3D dynamic torsional impedance at the pile cross-section with the adoption of the Laplace transform, variable separation, and impedance transfer method. The solution is then validated by comparisons against some widely-accepted existing solutions. The main conclusions of this study can be drawn as follows: (1). Classic one-dimensional theory overestimates the impedance of the pipe pile, which could result in severe disasters if the dynamic design is radical; (2). Even for small diameter pipe piles, the impedance would vary in the radial direction at the pile cross-section. Usually, the impedance at the outer radius would be slightly larger than that at the inner radius; (3). For large-diameter pipe piles or pipe piles with high-strength soil plugs, the most significant impedance could appear at the inner radius, indicating the resistance provided by the soil plugs can not be overlooked for large-diameter pipe piles.

Properties of soft Bangkok clay stabilized with cement and fly ash geopolymer for deep mixing application

Deep mixing (DM) is a technique for improving the ground that has been widely used worldwide. Ordinary Portland cement (C) has historically been the most popular binder for DM application; however, utilizing C releases a large carbon footprint. This research investigates the properties of soft Bangkok clay (SC) stabilized with C and high calcium fly ash (FA) geopolymer for high-strength soil–cement columns. The effect of influence parameters on the unconfined compressive strength (UCS) and scanning electron microscope (SEM) properties of SC-C-FA geopolymer specimens was measured. The specimens had initial water contents (w) of 1LL, 1.5LL, and 2LL, FA:C ratios ranged from 100:0–70:30, and sodium silicate:sodium hydroxide ratios (NS:NH) of 50:50, 70:30, and 80:20. The results indicated that the UCS of SC-C-FA geopolymer specimens was found to increase with the increasing C content. Whereas, the UCS decreased with the decreasing NS:NH ratios. The highest 28-day UCS of the specimen was obtained with initial water content of 1.5LL, FA:C ratio of 70:30, and NS:NH ratio of 50:50. The 28-day UCSs of SC-C-FA geopolymer with all initial water contents, C content greater than 5%, and NS:NH ratio of 50:50 passed the minimum UCS requirement for soil–cement columns. Furthermore, the equations for predicting UCS and carbon emissions of SC-C-FA geopolymer are very useful for designing soil–cement columns.

Macropores in a compacted soil impact maize growth at the seedling stage: Effects of pore diameter and density

Macropores are often regarded as preferential paths for root growth to bypass high-strength soil. However, the influence of macropore characteristics on root growth in compacted soils is not clearly understood. In this study, we investigated the effects of macropore diameter, density, wall surface area and porosity in a compacted soil on maize growth and N uptake at the seedling stage. Different diameters (0.5-, 1- and 2-mm) and densities (0, 1750, 3500, 7000 and 28,000 m−2 indicated by 0, 5, 10, 20, 80 numbers, respectively) of artificial macropores were created in compacted (1.6 g cm−3) soil columns (150 mm height × 60 mm internal diameter). The absence of macropores was treated as a Control. After 20 days of maize growth, the 3D root architecture and the interaction between roots and macropores were visualized and quantified using X-ray computed tomography (CT). The nitrogen uptake by plants from the compacted subsoil was determined using 15N tracer. Our results showed that the presence of 0.5- or 1-mm macropores enhanced maize growth and 15N uptake relative to the Control, but not the presence of 2-mm macropores. At a given macropore diameter of 0.5-mm, the effect of macropore density on maize growth and 15N uptake was in the order of 7000 m−2 > 28,000 m−2 and 1750 m−2. Under the same macropore wall surface area conditions (i.e., 2513 mm2 in this study), maize growth and 15N uptake decreased with increasing macropore diameter. Under the same macroporosity (i.e., 0.342% in this study), maize growth and 15N uptake were more promoted by macropore characteristics of 1-mm diameter with 7000 m−2 density and 0.5-mm diameter with 28,000 m−2 density compared with 2-mm diameter with 1750 m−2 density. CT images showed that the number of macropores colonized by roots and the intersecting area between roots and macropores both increased with increasing macropore density. Our results demonstrate that the presence of macropores can improve crop growth, but its effect depends on macropore characteristics created by appropriate macropore diameter and density (e.g., 0.5 mm diameter and 7000 m−2 density in this study).

Theoretical evidence that root penetration ability interacts with soil compaction regimes to affect nitrate capture.

Background and AimsAlthough root penetration of strong soils has been intensively studied at the scale of individual root axes, interactions between soil physical properties and soil foraging by whole plants are less clear. Here we investigate how variation in the penetration ability of distinct root classes and bulk density profiles common to real-world soils interact to affect soil foraging strategies.MethodsWe utilize the functional–structural plant model ‘OpenSimRoot’ to simulate the growth of maize (Zea mays) root systems with variable penetration ability of axial and lateral roots in soils with (1) uniform bulk density, (2) plow pans and (3) increasing bulk density with depth. We also modify the availability and leaching of nitrate to uncover reciprocal interactions between these factors and the capture of mobile resources.Key ResultsSoils with plow pans and bulk density gradients affected overall size, distribution and carbon costs of the root system. Soils with high bulk density at depth impeded rooting depth and reduced leaching of nitrate, thereby improving the coincidence of nitrogen and root length. While increasing penetration ability of either axial or lateral root classes produced root systems of comparable net length, improved penetration of axial roots increased allocation of root length in deeper soil, thereby amplifying N acquisition and shoot biomass. Although enhanced penetration ability of both root classes was associated with greater root system carbon costs, the benefit to plant fitness from improved soil exploration and resource capture offset these.ConclusionsWhile lateral roots comprise the bulk of root length, axial roots function as a scaffold determining the distribution of these laterals. In soils with high soil strength and leaching, root systems with enhanced penetration ability of axial roots have greater distribution of root length at depth, thereby improving capture of mobile resources.

Pseudo-static internal stability analysis of geosynthetic-reinforced earth slopes using horizontal slices method

ABSTRACT In this study, the well-established pseudo-static approach along with the horizontal slices method (HSM) is employed to investigate the seismic internal stability of geosynthetic-reinforced earth slopes. Previous simple HSM analyses were based on a primary assumption stating that the normal inter-slice forces are exerted on the mid-length of horizontal sections. However, this simplifying assumption could give rise to substantial errors in the calculation of design parameters, specifically in the case of high seismic excitations or low soil strength parameters. To address this deficiency, a balancing moment is considered as a new variable to account for the corresponding eccentricity. In the current HSM, two sets of unknown variables, including horizontal inter-slice forces and shear forces along failure surface, are determined using the well-known λ coefficient and the Mohr-Coulomb failure criterion. In this new technique, the traditional ‘5N-1ʹ type of HSM analysis is reduced to a robust and rigorous ‘3N’ one with the same predictive capability. The influence of various parameters, including soil characteristics, slope geometry and different earthquake coefficients are rigorously examined. Moreover, a number of useful graphs is provided to help engineers in the preliminary seismic design of geosynthetic-reinforced earth slopes.

Strength, swelling and compressibility of unsaturated sugarcane soils

Large-scale sugarcane plantation is characterized by successive and disordered traffic of heavy machinery and equipment over the cycle, which can cause damage to the soil structure. As the stress induced by traffic exceeds the soil load-bearing capacity, it results in soil compaction. However, the mechanisms and key variables that govern the compressive characteristics in agricultural unsaturated soils to support those applied loads without plastic deformations (compaction) is not fully understood. To investigate this process, we measured the strength, swelling and compressibility characteristics of unsaturated soils with contrasting texture from sugarcane fields. Undisturbed soil cores were sampled in nine cultivated sugarcane fields, equilibrated at a matric potential of –100 hPa and subjected to confined uniaxial compression tests. Precompression stress (σp), compression (λ) and swelling (κ) indexes were extracted from the soil compression curves. Soil organic C (SOC), degree of compactness, total porosity and particle size fractions were also measured and correlated to the compressive parameters σp, λ and κ. Principal components, correlation and multiple regression models were used to the data analyses. Overall, reductions in soil strength and increases in the soil compressibility and elasticity occurred with the increase in SOC, whereas increases in the degree of compactness resulted in higher soil strength and lower soil compressibility and elasticity. Furthermore, our results revealed that silt + clay content considerably increased soil compressibility. In combined scenarios for a range of soil texture, SOC and degree of compactness at matric potential at around field capacity (i.e. –100 hPa), the maximum σp observed was approximately 200 kPa, which is a much lower load-bearing capacity than the estimated stress for some trucks and trailers used in sugarcane harvest (∼600−800 kPa). Our study suggests that soil compaction is eminent in sugarcane fields at matric potential close to field capacity, and can be aggravated in clayey soils with high SOC content and low degree of compactness. Therefore, urgent strategies of traffic control are necessary to prevent or mitigate soil compaction induced by mechanized sugarcane operations.

Study on slope stability of frame prestressed anchor sheet pile wall with finite element strength reduction method

Slope stability analysis is performed in practical geotechnical engineering using the finite element method, which is an advanced method and is widely used by engineers. With the development of computer technology, it has become easy to study the slope's stability supported by frame prestressed anchor and sheet pile wall through the displacement-based finite element numerical analysis method, to calculate the safety factors. However, the expansion angle ψʹ is not widely covered. In this study, PLAXIS two-dimensional finite element method is using to establish the slope model supported by frame prestressed anchor and sheet pile wall, and the influence of expansion angle on slope deformation is studied. The results show that the expansion angle has a different effect on the convergence of the two-dimensional slope model. In the model slope, a prestressed frame anchor and sheet pile wall reinforce the slope. The failure mechanisms were unclear when ϕʹ= ψʹ (flow base). Besides, when the slope has high soil strength parameters (c' or φʹ), the expansion angle will affect the calculation results and convergence. In general, the expansion angle significantly influences the slope's stability and is not affected. Therefore, it was necessary to note the effect of the angle of expansion on stability.

Soil Management Systems to Overcome Multiple Constraints for Dryland Crops on Deep Sands in a Water Limited Environment on the South Coast of Western Australia

Deep sands on the south coast sandplain of Western Australia (WA) have multiple soil constraints including water repellence, high soil strength, low nutrient levels and subsoil acidity. The aim of the study was to test contrasting methods of managing water repellence and to assess their impacts on one or more soil constraints to crop production. These methods included seeding tyne design (knife point, winged points, paired row), soil wetting agent addition, strategic inversion tillage (rotary spading, mouldboard ploughing to 0.35 m) and clay-rich subsoil addition (170 t ha−1 with incorporation by spading to 0.20 or 0.35 m). Limesand (2 t ha−1) was applied as a split plot treatment prior to tillage. Cumulative crop yields were increased by 2.1–2.6 t ha−1 over five years by the strategic deep tillage and clay application treatments compared to the control. Water repellence was reduced by the inversion ploughing and subsoil clay addition treatments only. The effect of water repellence on crop establishment was expressed only in low rainfall years (Decile < 4) and mitigated by the paired row, wetting agent, spader and clay-amended treatments. In all years, plant numbers were adequate to achieve yield potential regardless of treatment. Soil K and plant tissue K and B were increased where clay had been applied. Inversion tillage reduced soil pH, organic carbon (OC) and macro nutrients in the 0–0.1 m layer although in most years there was no significant decline in plant tissue macro nutrient levels. Soil strength was reduced as a result of the inversion tillage to a depth of 0.35 m. However, the alleviation of soil strength and the crop yield responses diminished with time due to re-compaction. No crop response to the applied lime was found over five years at this site since the soil pHCaCl2 exceeded 4.7 within the root zone. In terms of soil constraints, we conclude that compaction was the dominant constraint at this site followed by water repellence and K deficiency.

Undrained bearing capacity of irregular T-bar by the lower bound method in clay

The lower bound method is employed to investigate the ultimate bearing capacity of the irregular T-bar in uniform soil. The stress field is constructed to illustrate the evolution of the soil flow mechanisms and considering the frictional influence. Simultaneously finite element analyses and two special conditions are also employed to verify the reasonability of the lower bound model. The general expressions of the bearing capacity factors for two types of irregular T-bars are presented, which have reference value for similar ocean structures. The main results are shown as follows: ①The friction coefficients significantly influence the bearing capacity factor with increasing aspect ratio. ② The rigid zones are presented at the front and rear of the elliptical probe and progressively decrease with increasing ξ (probe aspect ratios) and reducing ω (friction factor), until disappearing at a larger aspect ratio following a smooth interface. ③ For ξ > 1, the degree of streamlining of the elliptical probe easily results in an attached flow mechanism to the probe surface and a decreasing rigid zone with increasing ξ in the high strength soil. ④ Compared with the CPT test, the advantage of the diamond T-bar is without the need for overburden stress correction in the full flow mechanism. ⑤ The large aspect ratio of the irregular T-bar tries to determine the interface friction factor based on the bearing factor equation.

Engineering geology of residual soil derived from mudstone in Zimbabwe

As increasing amounts of civil engineering work are carried out on mudstone-derived residual soils, it has become important to systematically assess their geological engineering properties. Thus, the properties of mudstone-derived residual soils were evaluated in this study via a series of comprehensive laboratory tests to assess physical, mechanical, mineralogical, and microstructural variations. Results show that the physical properties of these soils are inadequate in terms of engineering applications; these soils can be classified as highly plastic clays that are hard to compact. Natural mudstone-derived residual soils undergo severe disintegration underwater while remolded examples are similar but tend to exhibit more stable responses. Natural mudstone-derived residual soils behave in a structured way when subjected to shear and compression; these soil types possess superior natural shear resistance but their strength decreases significantly following saturation as well as in wetting and drying cycles. Data show that the microstructures of mudstone-derived residual soils are characterized by the presence of aggregations with fissures; although iron-bearing cementation between these aggregations is responsible for high soil strength, bonds can be damaged, or even destroyed, when samples are saturated or subjected to wetting and drying cycles leading to a reduction in shear strength. The results of this research provide clear parameters for related engineering applications and enhance our understanding of residual mudstone-derived soils.

The influence of organic matter on the strength development of cement-stabilized marine soft clay

The organic matter within clay soil is one of the important factors affecting its engineering characteristics. In this study, the influence of organic matter on the strength evolution of cement-stabilized marine soft clay is evaluated by scanning electron microscopy (SEM) and unconfined compressive strength (UCS) testing. The experimental results show that the after-curing clay water content of the specimens increased with the organic matter content. However, the after-curing unit weight decreased with the organic matter content. The strength decreased with the increase in the amount of organic matter. The strength loss (SL) increased with the organic matter content. A new mathematical model was determined and then used to quantitatively analyze the strength of the investigated samples. A relationship between the strength and organic matter content was established. The evaluation of the accuracy of this new strength model was carried out by comparing the predicted values and measured values, and the results indicated that the deviation was mostly within 10%. Finally, the microscopic changes of the sample surface and influencing mechanism of the organic matter were revealed through SEM. A high soil strength is mainly due to a relatively low porosity, a dense microstructure and the formation of hydration products.

Influence of subsurface flow by Lidar DEMs and physical soil strength considering a simple hydrologic concept for shallow landslide instability mapping

High resolution DEMs and physical soil strength, among other factors, have significant effects on the shallow landslide instability mapping. Subsurface flow in soil mantle normally is assumed by slope parallel flow based on resolution of DEMs and, measuring soil strength, which is affected by subsurface flow within the soil mantle, is difficult in both the field and the laboratory. Thus, the aims of this study are to investigate the effect of subsurface flow by high resolution Lidar DEMs and the effect of physical soil strength attributes on shallow landslide instability mapping, respectively. In this study, two DEMs (with 1 m and 5 m resolutions) were used and, physical soil strength was calibrated using a simple subsurface hydrological concept with LiDAR and field survey data in order to quantify the influence of soil strength on shallow landslide instability mapping. To this end, various field surveys were performed at Woomyeon Mountain, Seoul, Republic of Korea, where shallow landslides occurred in 2012. The physical shallow landslide stability (SHALSTAB) model were applied. The modified success rate (MSR) method were applied to assess the predicted results. In the first series of simulations, using the two DEMs and experimentally derived soil strength values, relatively low MSR values of 0.42–0.468 for the 1 m DEM and 0.42–0.47 for the 5 m DEM were recorded. In the second series of simulations, using soil strength calibrated using a simple theoretical approach, the MSR for the 1 m DEM was 0.78–0.823 and the MSR for the 5 m DEM was 0.723–0.80. These results indicated that soil strength had a more important role in shallow landslide instability mapping than assuming subsurface flow by topographic resolution. Therefore, it may be useful to apply field-collected soil strength data using hydrological concepts to improve the accuracy of predictive models based on high-resolution surface data.

Effect of arbitrarily manipulated gap-graded granular particles on reinforcing foundation soil

It is generally known that high strength soil is indicative of well-graded particle size distribution. However, there are some special cases of firm ground despite poor grade distribution, especially a specific gap-graded soil. Based on these discoveries, this study investigated the development of an additive of gap-graded soils designed to increase soil strength. This theoretical concept was used to calculate the mixed ratio required for optimal soil strength of the ground sample. The gap-graded aggregate was added according to Plato\'s polyhedral theory and subsequently calculated ratio and soil strength characteristics were then compared to characteristics of the original soil sample through various test results. In addition, the underground stress transfer rate was measured according to the test conditions. The test results showed that the ground settlement and stress limit thickness were reduced with the incorporation of gap-graded soil. Further field tests would confirm the reproducibility and reliability of the technology by using gap-graded soil to reinforce soft ground of a new construction site. Gap-graded soil has the potential to reduce the construction cost and time of construction compared to other reinforcing methods.

Ammonium-Free Carbonate-Producing Bacteria as an Ecofriendly Soil Biostabilizer

Abstract In the current study, a novel ecofriendly soil biostabilizer was produced based on microbial-induced calcite precipitation. An aqueous solution of carbonate ions was produced by utilizing Sporoscarcina pasteurii bacteria under laboratory conditions. Natural zeolite was then utilized to remove the ammonium ions from the aqueous solution in order to prevent any harm from the ammonium ions to the soil environment, including vegetation and groundwater resources. It was observed that injection of calcium chloride followed by ammonium-free carbonate-producing bacteria increased the unconfined compressive strength of the soil. The scanning electron microscope image and energy dispersive X-ray spectroscopy spectra clearly showed that calcite crystals are precipitated at the soil pore, thus providing high soil strength. The calcium carbonate measurement exhibited homogeneous distribution of calcite along the length of the soil specimen.