Soil Improvement Methods Research Articles

Influence of Microbial-Induced Calcite Precipitation on Compaction Characteristics of Bioremediated Crude Oil Contaminated Soil using Composting Technique

Compaction as a soil improvement method of improving the engineering performance of soil was carried out on remediated contaminated soil with the aim of assessing the influence of microbial induced calcite precipitation (MICP) on compaction characteristics. Autochthonous bacteria was identified as Bacillus licheniformis and isolated from oil contaminated soil, collected from Kaduna refinery at Area W where the crude oil was stored. The bacteria were enhanced with organic liquid nutrient extracted from chicken droppings (CD) in stepped concentration of 10, 20, 30, and 40% by dried weight of soil sampleand used to hydrate the contaminated soil. The mixtures were kept in four microcosms for 3 months. The initial total hydrocarbon content was 98g/kg. The bioremediated soil was treated with bacteria solution through MICP technique. The results revealed that sample treated with 30% CD yielded the highest removal efficiency of 89.8% of oil removal. Maximum Dry Density increased with addition of B. licheniformis solution to a peak value of 1.93Mg/cm3 for sample treated with 1.5×108 cell/ml. Optimum moisture content (OMC) increased with increased in B. licheniformis suspension from 14.4 to 15.8% when treated with 1.5×108 and 2.4 ×109 cell/ml respectively. Compaction characteristics of soil treated with 30% CD were greatly improved at 1.5×108 cell/ml bacteria solution using MICP technology and could be used as liner material in waste management.

Microbially Induced Calcite Precipitation (MICP) for Stabilization of Desert Sand against the Wind-induced Erosion: A Parametric Study

Biocementation, based on microbially induced calcite precipitation (MICP), is a novel soil improvement method, which can form a cemented layer on the surface of desert sand to resist wind-induced erosion. In this work, the surface penetration resistance test and wind tunnel test were conducted to evaluate the various influential factors for the resistance of biocemented desert sand to wind-induced erosion, including the treatment factors, such as treatment temperature and biocement solution concentration, and durability factors such as the development of time, freezing–thawing cycles, and drying–wetting cycles. The test results demonstrated that the erosion resistance of biocemented desert sand was improved by the increase of treatment temperature and the concentration of biocement solution, which was manifested in the increase of surface penetration resistance of biocemented samples. In addition, the resistance of biocemented desert sand to wind-induced erosion decreased with the increased number of drying–wetting cycles, to lesser extents, with the development of time and the increased number of freezing–thawing cycles.

Applications of jet - grouting technology in the Metroline No.1 project at Ho Chi Minh City

The rapid development of economy and the booming urban population in large cities in Vietnam such as Hanoi and Hochiminh city lead to many urban problems of traffic jams and environmental pollutions such as dust and noise contaminations. These issuses effect directly on the health and the living of urban civilians in these cities. In order to solve these urgent transportation and social problems, some metroline projects recently have been carried out in Hanoi and Hochiminh city to meet the high urban transportation demands and to solve congestion problems. Since some Metro line projects in Hanoi and Hochiminh city have been carried out in soft soil conditions, ground improvement methods become a necessary requirement in these projects for ensuring the success of metroline projects and avoiding any potential damage occurred in the tunnelling process. A state - of - the - art soil improvement method with the jet - grouting technology has been applied in Hochiminh Metroline No.1 project with purposes of stabilizing the tunnelling process and protecting nearby existing buildings. This paper presents some applications of the jet - grouting technology when tunnelling by an earth pressure balance tunnel boring machine in the Hochiminh Metroline No. 1 project at the starting and arriving shaft areas for stabilizing the tunnelling process as well as at the Saigon Municipal Opera House area in Hochiminh city with a role of protecting method for the important historical building. By collecting design and site data combining with the analysis of the experimental and observed data obtained from the Hochiminh Metroline No.1 project, the stdy results show the effectiveness of the jet - grouting technology when applying in tunnelling projects with soft soil conditions in Vietnam. The results are also a designing reference for near future metroline project in Hanoi and Hochiminh city.

Laboratory Experiments and Numerical Simulation Study of Composite-Material-Modified Loess Improving High-Speed Railway Subgrade.

Construction of high-speed railway subgrade on loess soils in the Loess Plateau is risky because such soil is susceptible to differential settlements. Various soil-improvement methods have been used to enhance the mechanical properties of loess. Lime-ash soil and cement-lime soil are the most commonly used methods in the improvement of loess subgrade, while few studies have been found on loess subgrade improvement by using composite material consisting of traditional materials and new materials. A series of direct shear tests and unconfined compressive tests were conducted on the loess specimen with the addition of three kinds of composite materials: traditional material cement, new material polypropylene fiber and SCA-2 soil curing agent. The numerical simulation was conducted on loess subgrade in an actual engineering practice. The experimental results show that cement, polypropylene fiber and SCA-2 soil curing agent can effectively improve the shear strength and compressive strength of loess, and the influence degree is cement > fiber > curing agent. Additionally, based on the relative strength characteristics of the improved loess, an optimal improvement scheme for the composite-material-modified loess was obtained: 16% cement content + 0.5% fiber content + 4% curing agent content. The numerical simulation results revealed that the compressive strength index of the improved loess has a significant impact on the subgrade settlement, and the optimal improvement scheme obtained from comprehensive analysis can effectively improve the settlement of high-speed railway subgrade under vibration load.

The Performance of Ca(OH)2 to Reduce the Plasticity Index and Increase the Shear Strength Parameter for Expansive Soil

The design on expansive soils can easily change in volume due to the influence of water content. This makes it necessary to consider soil improvement methods in the planning process to maintain the variation in the water content. One of these methods includes chemical stabilization, which is carried out by adding materials such as cement or lime. In expansive soils, stabilization efforts aim to reduce the plasticity index and increase the shear strength parameters. Therefore, this study focused on the addition of slaked lime (Ca(OH)2) to expansive soil in Lakarsantri, Surabaya. The stabilizing materials used contain calcium to form pozzolan in the clay and increase the bearing capacity parameter, which is variation in shear strength. The soil was taken at 2 points A and B with a different moisture content of 48.57% and 35.12%, as well as a high plasticity index value > 50% using a percentage (Ca(OH)2) of 6%-24% at a certain curing time. Based on the results, the plasticity index in the soil changed from very high to moderate with an optimum percentage value of 6% at 30 days of curing time. The optimum value of soil shear strength is (Ca(OH)2) 6% at 30 days of age in soil A, the cohesion value is 0.02 kg/cm2, and an internal shear angle of 36°. In soil B, the optimum shear strength obtained (Ca(OH)2) was 6% at the age of 10 days with a cohesion value of 0.14 kg/cm2 and an internal shear angle of 23.80°. Therefore, the results of this study show that the parameter of shear strength of the soil from the cohesion value showed that the cohesion value decreased with the addition of Ca(OH)2, while the internal shear angle increased.

Reliability based predictive model for estimating shear strength values of locust bean waste ash compacted black cotton soil

A cheap and eco-friendly method of soil improvement is vital in achieving a reduction in the negative effect of climate change and cost of construction. Black cotton soil (BCS)–locust bean waste ash (LBWA) blend was evaluated via laboratory test, thereafter subjected the results to computer base program. Soil was treated with 0, 2, 4, 6, 8 and 10% LBWA by dry weight and compacted with different energies. A regression equation was developed from the laboratory measured values to serve as a limit state equation and integrated into a FORTRAN program, to generate safety index (SI) for shear strength values in the range of coefficient of variation (COV) of 10–100%. Results of statistical analysis show strong interaction between the shear strength values and the soil parameters (Locust bean waste ash, LBWA; Cohesion, CO; Friction angle, FA; Plasticity index, PI; Maximum dry density, MDD; Optimum moisture content, OMC; Percentage fine, PF; Cation exchange capacity, CEC; Specific gravity,Gs and Compactive effort, CE).Results show that for the laboratory model, safety indices are sensitive to changes in all the parameters considered. Results showed that among the entire variables, MDD, PI and OMC have major effect denoted by wide variations in their safety indices, seriously influenced by the COV. Safety indices for the effect of LBWA changed from −0.263 to −0.256, −0.134 to −0.13 and 0.00253 to −0.00246 for BSL,WAS and BSH, in that order. Aslo, values for untreated soil changed from −1.19 to −1.17, −1.08 to −1.06 and −0.973 to −0.954 for BSL, WAS and BSH, in that order. Similar pattern was recorded for other variables. Results obtained fell to meet up with the minimum regulatory value of 1.0 as stated by the Nordic Committee on Build Regulations at 10–100% COV as expected. The recorded safety indices for all the independent variables considered shows higher values when compared to that of the untreated soil. A more effective additive such as cement or lime blended with LBWA is commended to model shear strength values of the modified soil for dams or embankment applications.

Utilization of Dredged Mud in Land Reclamation: A Comparison Study of Several Soil Improvement Methods

Utilization of dredged mud in land reclamation will become more applicable in the future due to the increase of the need for space and the rising cost of granular fill materials. Dredged mud mainly consists of soft clay and has very low bearing capacity and high compressibility. Therefore, soil improvement is urgently required. In this paper, the effectiveness of using dredged mud as the fill material in land reclamation was analyzed for a case study of land reclamation. The performance of several soil improvement methods in using such reclamation material was calculated and compared. The soil improvement methods considered in this study were prefabricated vertical drain (PVD) with vacuum preloading, cement mixed dredged mud, and rigid inclusion. The load transfer mechanism in each method was analyzed using analytical and numerical methods. In addition, an elementary cost analysis was performed to compare the cost of the methods based on Indonesian prices. It was found that for the considered case study, cement mixing achieved the highest bearing capacity with the shortest time but with the highest cost. For the same increase in bearing capacity, PVD with vacuum preloading provided the lowest cost. This study provides a preliminary step towards the implementation of effective soil improvement for land reclamation in Indonesia.

Experimental Investigation on the Variation in Shear Strength of Clayey Soil Reinforced with Randomly Distributed Alkali-Resistant Glass Fiber

Geotechnical investigations are one of the most crucial parts of the construction to save the time and effort spent on the projects. Particularly, in the case of the clays with high plasticity are encountered, the analysis of bearing capacity and settlement of structures such as buildings, roads, and dams governs the design. The possible solutions can be leaving the land, reaching a strong soil bypassing the weak one, removing the weak soil by replacing it with a higher strength of the material, and applying soil improvement methods. Glass fibers are one of the synthetic additives which may be used to address improving the weak soil properties. In this study, the effect of alkaline-resistant glass fiber additive on the undrained shear strength of the clayey soils was investigated. Fibers with distinct lengths were added to the natural soil at increasing rates, and the mixtures were prepared in the optimum water content. The prepared mixtures were compacted in a compaction mold with a diameter of 50 mm and a height of 100 mm with standard energy. Unconfined compression test (UC) were conducted on a total of 210 cylindrical samples, 10 of natural clay and 200 of fiber-reinforced. The maximum increase was at 0.5% of a fiber blend of 40 mm length. As a result of 210 UC tests, it was observed that the alkaline-resistant glass fiber additive increased the shear strength of the clay soil.

Stabilizers Effects Comprehensive Assessment on the Physical and Chemical Properties of Soft Clays

Deep soil mixing (DSM) is one of the practical methods of soil improvement in the world, which produces cement columns and modification by injecting stabilizing materials such as cement or lime using a mechanically hollow shaft drill in the soil. In this method, the soil characteristics are improved by mixing the soil with cementitious materials by deep mixers and creating cement soil columns. In addition, by overlapping the columns before full setting, continuous walls can be constructed below the ground. The aim of this study was to investigate the effect of the additive type on the strength of the samples. For soil samples stabilized with lime, the maximum value of uniaxial resistance was 247 kPa and for the mixture of 10% lime and 4% sodium silicate was obtained.

LABORATORY MODEL DESIGN FOR DEEP SOIL MIXING METHOD

One of the most critical problems in the construction sector is the inadequate bearing capacities of subsoils. To solve this problem, various soil improvement methods are employed. Soil improvement is defined as the improvement in soil properties to the desired level by using various methods when the soil is not suitable for superstructure loads. Various types of soil improvement methods exist, and their application depends on the construction site, soil properties, earthquake zone, application time, and cost. One of the most widely used methods recently is the deep soil mixing method. In this study, a laboratory-scale deep soil mixing device is first developed; subsequently, the effects of injection pressure, mixing time, and dosing parameters on application are investigated. Deep soil mixing columns are prepared using different injection pressures, mixing times, and dosages and then subjected to the unconfined compression test. Results show that the effects of injection pressure, cement dosage, and mixing time on the unconfined compressive strength of deep soil mixing samples vary based on the initial soil properties.

Modifikasi Perbaikan Tanah Dasar Tol Semarang–Demak: Metode Vacuum Preloading dengan Prefabricated Vertical Drain

The Semarang-Demak Toll Road Development Project provides information that conditions in these areas were dominated by rice fields and swamps with high groundwater levels. At STA 21+000 to 22+350, the subgrade was very soft to a depth of 24 m, so subgrade improvement needs to be done to eliminate soil compression. The soil improvement method used was Vacuum Preloading with Prefabricated Vertical Drain. The results of the planning showed that the installation of a vacuum pump at the project site has a pressure of 101.28 kPa. The effectiveness of the pump was 80%, making the vacuum pressure 81.02 kPa or the equivalent of 4.89 meters of soil pile. The square PVD installation pattern with a distance of 100 cm was chosen on the basis of consideration of the consolidation time. This design reduces the time it takes for the soil to reach a 90% degree of consolidation, from 256 years to 16 weeks. The Vacuum Preloading method reduces the heap height, as in STA 21+950. This method also creates a subgrade embankment of only 7,767 m.

Polymer-assisted enzyme induced carbonate precipitation for non-ammonia emission soil stabilization

Biocementation using enzyme induced carbonate precipitation (EICP) process has become an innovative method for soil improvement. One of the major limitations in scaling-up of biocement treatment is the emission of gaseous ammonia during the urea hydrolysis, which is environmentally hazardous. In order to eliminate this shortcoming, this paper presents a series of experiments performed to evaluate a novel approach for preventing the ammonia byproducts in the EICP process via the use of polyacrylic acid (PAA). Through the adjustment of the pH to acidic, PAA not only promotes the enzyme activity, but also averts the conversion of ammonium to gaseous ammonia and its release, thus preventing any harm to the environment. The sand samples were treated with cementation solution and assessed for improvement in strength. Calcium carbonate content measurements and X-ray powder diffraction analysis identified the calcite crystals precipitated in the soil pores. Scanning electron microscopy analysis clearly showed that calcium carbonate was precipitated connecting soil particles, thus providing a uniaxial compressive strength (UCS) of up to 1.65 MPa. Overall, the inhibition in the speciation of gaseous ammonia shows the great potential of PAA for large-scale promotion of biocement.

Applying Multiwall Carbon Nanotube for Increasing Soil Bearing Capacity

Nanotechnology is an alternative in soil improvement methods. The size of the nanoparticles is very small, ranging from 1 to 100 nm. Multiwall Nanotube is one of the nano materials in increasing the bearing capacity of the soil. According to Arabania et al. (2012), the strength of clayey sand increased by 120% by adding 3% Multiwall Carbon Nanotube. Meanwhile, according to Taha (2012), the recommended addition of Multiwall Nanotube Carbon is 0.1-0.5%. This research uses Unconfined Compression Test to determine the unconfined compressive strength (qu) and undrained shear strength (cu) of the land. Key words: nano, multiwall nanotube, multiwall nanotube carbon, unconfined compression test, undrained

A cleaner biocementation method of soil via microbially induced struvite precipitation: A experimental and numerical analysis

Microbial-induced struvite precipitation (MISP) is a new biocementation method for soil improvement and hydraulic permeability reduction. Compared with traditional microbial-induced carbonate precipitation (MICP), MISP can significantly reduce the production of harmful ammonium ions during biochemical reactions and convert ammonium ions into struvite with promising mechanical strength. In this study, a series of experiments were conducted to compare the performance of the MICP and the MISP processes on sandy soils. Results showed that the average content of calcium carbonate in MISP cemented sand columns after 3 times of injection is similar to that in MICP cemented sand columns after 9 times of injection. The hydraulic permeability of MISP cemented sand columns after 3 times of injection is an order of magnitude lower than that of MICP cemented sand columns after 9 times of injection. To further investigate the physicochemical interactions during MISP and MICP processes, a one-dimensional finite element code considering the chemical reactions and the solute transportation was proposed. Results show that most of the MISP were formed in the early 3 h of the 6 h injection cycle, whereas most of the MICP were formed in the last 5 h of the injection cycle. The simulated total mass of the MISP precipitation, 11.3 g, was close to the experimental result of 9.6 g. The spatial distribution of MISP is more uneven as compared to MICP, as a result of the much faster reaction rate of struvite than calcium carbonate. The findings suggested that MISP could partially replace MICP in the applications of leakage mitigation and reinforcement of sandy soils.

Comparison of soil improvement methods using crude soybean enzyme, bacterial enzyme or bacteria-induced carbonate precipitation

Either microbial or enzyme-induced carbonate precipitation (MICP or EICP) has emerged to provide an alternative to cement-based ground improvement methods. For EICP, either plant urease or bacterial enzyme can be used. The effect of treatments can differ when different methods are adopted. In this study, the soil improvement effects for three methods were compared. The newly developed one-phase–low-pH method was adopted for both the MICP and EICP processes in this study. The crude urease enzyme was extracted from soybean and urease-producing bacteria. The results show that the amount of calcium carbonate induced by the crude soybean urease enzyme is comparable to that produced by bacteria or bacterial urease under the same urease activity. However, the treatment using the crude soybean urease enzyme has the advantage of being more effective in enhancing the strength and reducing the permeability of soil than the other two treatments, especially for soil with small grain sizes. This can be explained by the difference in the precipitation pattern of calcium carbonate using various urea hydrolysis media.

Observations from Ground Improvement Using Vacuum Consolidation Method

In the modern world of Civil Engineering, challenges arise during the various phases of construction, starting from the project development phase to the completion of the project. One of the main factors to be considered before commencing any infrastructure project is the foundation of where it is to be built. Without a strong foundation, it's not possible to proceed further to subsequent stages and in some cases, significant improvements may be required before starting the construction process. Although there are several different available methods for soil improvement in Civil Engineering, preloading using vacuum pressure with prefabricated vertical drains (Vacuum Consolidation Method) is one of the commonly applied techniques. Nowadays, it is widely used in countries having soft soil settlement problems. This paper presents the observations made from a soil improvement project using VCM including the site conditions and methodologies adopted during the process. The field data related to parameters such as pore pressure, settlement and shear strength improvement in natural soft clay have been presented and discussed. The degree of consolidation in the field has been back-calculated from settlement data and compared with values obtained from the 1-D consolidation equation. Field investigation tests, such as borehole tests and field vane shear tests, were performed before and after the soil improvement and it was found that the soft soil properties can be enhanced using vacuum consolidation without the use of any surcharge loading as well.

Effect of Partial Saturation on Ultimate Bearing Capacity of Skirted Foundations

Skirted foundations are one of the solutions proposed to increase the bearing capacity of the soil. They assist in increasing the load and depth of failure in weak ground or soils with low shear resistance and reducing the foundation settlement if a soil improvement method cannot be applied or the cost of implementing deep foundations increases. This study examined and investigated the extent of soil bearing of skirted foundations on sandy soils and studied the effect of soil saturation cases and three cases of water content reduction to measure the matric suction value of unsaturated soil. A physical model was created to simulate the strip foundation and compare these cases (dry-fully saturated-partially saturated). It was found that the soil load carrying capacity in the case of unsaturated soil is the highest, where matric suction is at a depth of 450 mm, followed by the dry case and then the saturated case as it represents the weakest state of the soil.

Impact of organic amendments on the bioavailability of heavy metals in mudflat soil and their uptake by maize.

Organic amendments (OAs) can be a sustainable and effective method for mudflat soil improvement. A field experiment was conducted to investigate the potential of OA application to mudflat soil improvement. We measured the pH, soil organic matter (SOM), salinity, maize growth, and heavy metal (HM) accumulation in OA-applied soils, and maize tissues after three OAs, sewage sludge (SS), Chinese medical residue (CMR), and cattle manure (CM), were applied at the application rates of 0, 30, 75, 150, and 300 t ha-1. OA application significantly increased the SOM and decreased the pH and salinity of mudflat soils. The maize biomass and HM contents in soil and maize increased after OA application. The bioavailability and bioconcentration of HMs were generally in the sequence of SS > CMR > CM. The average bioavailability ratios of HMs were in the order of Cd > Zn > Cu > Mn > Ni. The bioconcentration of Zn and Cd by maize was highest, followed by Mn, Cu, and Ni. SOM, pH, and salinity were the important factors regulating soil available HMs and, subsequently, HM accumulation in maize. Among the three OAs, SS is most effective in decreasing soil salinity, and increasing the SOM, bioavailability, and bioconcentration of HMs. On the other hand, CM was the best OA because it promoted significant maize growth yet maintained low HM contamination risk.

Pengaruh Dissolved Organic Carbon (DOC) pada Efektivitas Perbaikan Tanah Gambut dengan Metode Calcite Precipitation

The problems that are generally found in land preparation for infrastructure developments are the characteristics of soils that have low bearing capacity, such as peat soils. Calcite precipitation is a soil improvement method that utilizes biochemical reactions with the final product being calcite. Peat soil has different characteristics from other soils, that it has high levels of Dissolved Organic Carbon (DOC). The amount of DOC present in peat soil significantly affects the specific gravity, liquid limit, density, and strength of the soil. Therefore, it is necessary to evaluate whether DOC in peat soil can affect the effectiveness of the calcite precipitation method. The research was conducted on soil with high organic content (95.35%) and soil with moderate organic content (73,51%). The research was carried out through five stages, namely soil properties, test-tube experiment, soil samples treatment, Unconfined Compressive Strength (UCS) test, and evaluating the soil pH. The results of this study obtained in the form of high organic content have an additional strength of 76.47%. Medium organic content soil has an additional strength of 137.50. Thus, DOC has an effect on increasing soil strength in the calcite precipitation method.

Hyperspectral imaging for small-scale analysis of Hordeum vulgare L. leaves under the benzo[a]pyrene effect.

Hyperspectral imaging is a newly developed approach to estimate the current state of the plants and to develop the methods of soil and plant ecological state improvement under the effect of different sources. The study was devoted to the novel approach of hyperspectral imaging application in the case of persistent organic pollutants (POP) uptake by plants. Hordeum vulgare L. was used as a test plant and grown on the soil artificially contaminated by benzo[a]pyrene (BaP) in the doses of 20, 100, 200, 400, and 800ngg-1, which corresponds to 1, 5, 10, 20, and 40 maximum permissible concentrations (MPC) and correlates with the level of soil pollution near industrial facilities in the Rostov Region (Russian Federation). It was analyzed a group of indexes responsible for plants stress, consists of broadband greenness group, narrowband greenness group, light use efficiency group, and leaf pigments group. Benzo[a]pyrene had a stronger effect on the efficiency of the photosynthesis process than on the content of chlorophylls. In the phase of active adaptation to stress in H. vulgare, the content of photosynthetic pigments was increased. The proposed method for selecting spectral profiles by cutting off profiles that do not belong to a plant, based on the NDVI value can be effectively used for the estimation of the plants stress under the BaP contamination and for future perspectives in the most suitable way for the application of the plant's growth stimulants.