Soil Improvement Methods Research Articles

The Effect of Reinforcement of Bamboo Matting, Bamboo Grids, and Geotextiles on Non-Woven Increasing the Carrying Capacity of Clay Soil Using the Loading Test

Nowadays, various soil improvement methods have been developed. One of them is the soil reinforcement method as an alternative solution to subsidence and low soil bearing capacity. This study aimed to determine the effect of reinforcing bamboo mats, bamboo grids, and geotextiles non-woven on increasing the bearing capacity of clay soil and comparing the bearing capacity of each variation with the value of the bearing capacity without reinforcement. This research is an experimental study using the loading method with the modeling of the underburdened soil conditions. This study uses woven bamboo reinforcement, bamboo grids, and geotextiles non-woven. Each effect of the reinforcing material on the clay is sought for the ultimate bearing capacity value. The results showed that: (1) the type of soil according to the USCS classification in Kalangan Hamlet, Bangunjiwo Village, Kasihan District, Bantul Regency, Yogyakarta Special Region is inorganic clay with high plasticity, fat clays with code CH (high clay plasticity). According to AASHTO, the soil classified in group A-7-6 (40), (2) the addition of reinforcing bamboo mats, grids bamboo, and geotextiles non-woven can increase the ultimate bearing strength (3) strengthening the bamboo grid can provide an increase in value. The ultimate bearing strength (qult), which is dominant, is 3.4 times that of the original soil without reinforcement with a bearing capacity ratio (BCR) of 3.44 or a 234.43% increase in percentage. This study shows that bamboo is more effective in transferring and spreading loads to the soil.

Evaluation of the Organic Soil Compressibility from In-Situ and Laboratory Tests for Road Application

Organic soil is characterised by high compressibility and should be improved so that it can be used for construction. The use of every method of soil improvement requires knowledge of the compressibility parameters. One of these parameters is the constrained modulus. The constrained modulus can be determined using laboratory or in-situ tests. In this study, the constrained modulus of organic soil was determined using oedometer and piezocone tests (CPTU). The author analysed subsoil under an approximately 250 m section of a designed road in north-eastern Poland. The constrained modulus of organic soil sampled from four different depths was determined in oedometer tests. Piezocone tests were conducted at 18 points located every 15 m along the length of the section concerned. To determine the constrained modulus based on the cone resistance from CPTU tests, the knowledge of the α and αM coefficients is needed. For the tested soil, the optimal range of the α coefficient from 0.4 to 0.7 was determined. The αM coefficient ranged from 0.4 to 0.8. The value of the constrained modulus of organic soil obtained from the oedometer tests, depending on the effective stress, ranged from approximately 100 kPa to 400 kPa. The constrained modulus of the tested soil decreased with depth, which both research methods proved.

A Review article on Construction, Parametric Study and Settlement Behavior of Stone Column

The various geotechnical construction technique is being primarily used of the ground improvement. The current advancement of industrial and urban growth and also the need for the wider access to the land have resulted in the development of various soil improvement methods. Stone column happens to be one among the best possible available methods for the improvement of soft/weak soil. This paper tries to indicate the review of the ground improvement by one of the existing method of stone column from the already present literature and standards. In this method, the soft soil is being enforced with a column of stone which is installed in the system. The high permeability of the stone column’s material portion not only increases the soil’s load carrying capability, but also decreases soil settlement, up to a certain extent and thus minimizes the settlement to occur after the construction. In order to reach this goal, various essential characteristics of stone columns have been considered in relation to design parameters.

A Review on Deep mixing method for soil improvement

Deep mixing method, the ideal choice that can be used to treat problems arising from the presence of soft clay soil as a basis for constructing a specific structure. Soft clay soil covers large areas in some countries around the world, making it difficult to find suitable places for construction. Soft clay soil which has a high moisture content that makes it with small shear resistance and high settlement capability is not suitable as a bearing layer under the foundations of the facilities, Therefore, the need arose to either the use of a certain type of foundation, such as deep foundations Which are more complicated compared to the second option, or the use a specific treatment technique to improve the properties of the soft clay soil and make it suitable for the construction with the using of a certain type of foundations other than deep foundations. One of the most suitable treatment techniques for soft clay soils in terms of structural purpose, cost and time is the deep mixing process. Deep soil mixing is a complex process in terms of factors that affect the improved soil quality and the processes that causing the improvement. This process has been covered in a lot of books and published researches in many of its aspects, but there is some of that relates to this process has not been significantly highlighted such as improved soil permanence over time, which causes a poor understanding of the behavior of improved soil after the improvement process. In this research paper, everything related to the deep mixing process will be touch upon, starting with the historical development of this process, its beginnings to its types, classifications and applications, and the accompanying chemical and physical processes, in addition to a literary review for what related to this process.

Effect of wetting and drying cycles on the durability of bio-cemented soil of expressway slope

Cyclic wet-dry is one of the influential weathering agents which can rapidly alter the mechanical properties of soils, limiting their durability and consistent performance. This study investigates the effect of wet-dry cycles on the mechanical behaviour of bio-cemented soil. Microbial-induced carbonate precipitation-based bio-cementation is an innovative soil improvement method, which is gaining increasing attention as a potential alternative for stabilizing slope surface. As the treated surfaces are exposed to repeated rainfalls and draughts, durability analysis is essential; cyclic wet-dry tests were therefore performed as a credible indicator of durability. The soil obtained from the Hokkaido expressway slope was treated at laboratory to varying cementation levels (% CaCO3) and subjected to 50 subsequent wet-dry cycles. Physical and mechanical changes were monitored using mass loss, shear wave velocities and needle penetration tests during wet-dry cycles. The results showed that the wet-dry cycles deteriorated the physical and mechanical at two stages. The mass and S-wave velocity of specimens significantly dropped after first few cycles and then tended to reach equilibrium. The second stage of notable deterioration was observed between 30 and 50 wet-dry cycles. It is suggested that the erosion of weak and powdery deposition of CaCO3 causes the degradation at the early stage, whereas the degradation in the late stage was attributed to the microstructural deformations of intact carbonate bonds. It was also found that the increase in cementation level decreases the deterioration of bio-cemented soil under wet-dry cycles.

Maxwell model geotextile encased stone column in soft soil improvement

In the field of geotechnical – soft soil improvement, the mathematical model or mechanical model is one of the important input parameters for the design calculations or studies. The determination of the appropriateness of the models has a great influence on the accuracy results of design and calculation as well as the sustainable stability of soft ground after improvement. On the contrary, the selection of inadequate calculation models will lead to increased costs of soft soil improvement, possibly even leading to the destabilization of the work and causing immense loss of people and property. Recently, many projects major highway after construction design in use has not meet the requirements of the standard, leading to wasted money and time of individuals, organizations, and the state of post-treatment. Therefore, the research and application of using mathematical or mechanical models in accordance with the new soft soil improvement method will greatly help as well as add additional options for soft soil improvement in Vietnam. The soft soil deformation is not only related to load but also to load time. The change in stress and deformation of weak soil over time is called rheology, and in this study is the viscoelastic behavior. From the above reasons, we try to apply a generalized Maxwell model to explain the viscoelastic behavior of a soft soil. In particular, the time-dependent behavior of a viscoelastic soft soil was represented by using the Maxwell rheological model. The Matlab programming code helps to solve numerically all the equation of the mathematical exhibition of the generalized Maxwell model results. We acknowledge that the generalized Maxwell model is superior in demonstrating the time-dependent behavior of soft soil. The results probably show that this is one of the effective models to predict the behavior of soft soils in ground improvement with GEC.

Role of Geotechnical Engineering in BIM process modelling

BIM “Building Information Model” creates a significant step forward in the whole process of construction. The role of geotechnical engineering will be shown as for classical building engineering so for civil engineering structures. In the first case all upper structures are in interaction with ground (subsoil), when foundation structures are basic element of this interaction. The 3D Ground model and 3D Foundation structure model create therefore one of the first individual parametric elements around basic (coordinating) BIM model. Some specificity will be shown as the impact of step by step creation (nD dimension) of the Ground model for the earliest building conception. Roughly the same is valid for civil engineering structures. Some specificity will be shown for earth structures of transport engineering, as a selection of borrow pit, definition of soil compaction for fill, fill compaction or any other methods of soil improvement and its control as they create important elements for the safe and optimal embankment design and performance. Final 3D Ground model together with 3D Geotechnical structure model (real performance) create the important base for the future decision making, when some changes will occur.

Consolidation settlement calculation and examination of the foundation settlements with finite elements method, example of Batman city Gültepe bridge

In this study, geological and geotechnical studies were carried out on the soil of a bridge built in 2015 in the Gültepe District of Batman City, located in southeastern Turkey, to perform the foundation settlement calculation. For this purpose, four foundation boreholes were drilled to determine the engineering parameters of the soil, and triaxial pressure and consolidation tests were carried out on the obtained samples. The consolidation settlement calculation was made in accordance with these parameters. Using the same data, numerical analysis was performed with PLAXIS V.8.2 (Finite Element Code for Soil and Rock Analyses), a two-dimensional finite element package program. The consolidation settlement value was calculated by performing dynamic analysis based on time in the computer software. The settlement value was determined to be 1.70 cm after the analysis, and it was evaluated by correlating with the consolidation settlement analysis results made according to Bowles (1988). Consolidation settlement calculations and finite element package program analyses gave similar results. We observed liquefaction risk and settlements in the structures with shallow foundations in the residential zone near the study area since the soils in the study area consist of silty sand of 5-10 meters and have groundwater. The Bored Pile technique, which is one of the soil improvement methods, was applied and discussed in order to determine the geological problems in the study field.

The Effects of Pine Tree Sawdust on the Volume Compressibility of Expansive Soils

Expansive soils are very important natural geological materials used in the geotechnical applications in the worldwide. After compacting, they are used as hydraulic barriers in earth structures, such as core of earth fill dams, landfill liners, and etc. However, these soils have some defects from technical points of view. To remove the defects, one of the soil improvement methods is mixing of these soils with granular materials. In this study, pine tree sawdust was used as granular additive material to stabilize the expansive soils. The effects of pine saw dust on the volume compressibility of expansive soils were investigated by using experimental studies under laboratory conditions. The test results showed that the pine saw dust positively affected the geotechnical properties in term of volume compressibility manner. As a consequently, the geotechnical properties of the expansive soil when blended with pine tree sawdust indicates that the pine tree sawdust is a good modification material for this problematic soil.

Microbial-Induced Calcite Precipitation Study on the Plasticity and Compaction Characteristics of Lateritic Soil Treated with Bacillus Megaterium in Urea-CaCl2 Culture Medium

An ecofriendly method of soil improvement known as Microbial Induced Calcite Precipitation (MICP) has received significant recognition in the past decade. This study presents a report on the capability of MICP in modifying the plasticity and compaction properties of lateritic soil bio-treated with different suspension densities of a ureolytic microorganisms - Bacillus megaterium (B. megaterium). Specimens were prepared with liquid limit moisture of the natural soil in three mix ratios of B. megaterium (B) and cementation reagent (C) (urea medium): 25 % B: 75 % C, 50 % B: 50 % C and 75 % B: 25 % C. Another set of specimens were prepared at optimum moisture content (OMC) equivalent covering 1/3 pore volume of B. megaterium and 2/3 pore volume of urea medium introduced in three sequences at 6-hour interval to steadily initiate MICP mechanisms. The results of the various mix ratios indicated improvement in plasticity index (PI) with higher B. megaterium suspension density. The best improved PI value was obtained for specimen treated with 75 % B: 25 % C mix ratio at B. megaterium suspension density of 2.40 × 109 cells/ml with an equivalent maximum 5.3 % CaCO3 content. The maximum dry density (MDD) and OMC values marginally increased with higher B. megaterium suspension density as well as calcite content. The micrographs obtained from scan electron microscope (SEM) showed changes from untreated to bio-treated state, which resulted in non-uniform precipitation of calcite in the soil. The variation in elemental quantifications displayed by the X-ray energy dispersive spectroscopy (EDS) validate the formation of calcite within voids and on surface of the soil particles.

Effect of Hydrocarbon Contamination on Biostabilization of Soil Contaminated with Motor Oil and Gasoline

Environmental problems caused by soil contamination can cause changes in the physical, chemical and geotechnical properties of the soil. Research on a suitable method for soil improvement has focused on the use of biological methods for soil improvement and remediation. Microbial calcium carbonate precipitation has been applied to solve many geotechnical problems. In this study, sandy soil was mixed with two conventional hydrocarbon pollutants and classic soil mechanics tests (compaction, direct shear, uniaxial and permeability tests) were implemented. The use of two bacterial solutions, two-phase injection and bacterial flocculation with injection of cementation solution, produced favorable results. Considering the lower inhibition of gasoline in low dilution, it was possible to improve with both methods. In the case of soil contaminated with motor oil, limitations on the use of microbial calcium carbonate precipitation were improved with the use of bacterial flocculation. The results of this approach were more suitable because the bacteria stabilized between the soil grains. XRD, SEM, EDS and wet chemical analysis were carried out to help confirm and interpret the results.

Effect of Freeze-Thaw on Compressive Strength of Clayey Soils Reinforced with Wool

ABSTRACT Reinforcing clayey soil using synthetic and natural fibers has been widely used as soil improvement methods in recent years. The usage of wool, which is inside the natural fibers, as a reinforcing material is seen as an economic, sustainable, and environmentally friendly solution. The compressive strength parameters of clayey soils (CS) equipped with wool were determined by a series of free pressure strength tests before and after freeze-thaw (F-T). The F-T cycle was repeated 12 times in cycles 1, 7, and 28 days. The highest strength increase was attained after 28 days of curing. The compressive strength increase of CS samples prepared with four different wool additives (0.5%, 1%, 1.5%, and 2% dry weight) occurred between 16.9–68.7% and 13.3–62.7% before and after F-T, respectively. The highest compressive strength increase before and after F-T occurred in CS+1.5% wool mixture. In addition, the wool ratio and the number of freeze-thaw cycles were determined to be important parameters in the increase in compressive strength. In summary, it is concluded that wool-supported CS can be used in the basic design of engineering structures and in shallow depths especially in regions with cold climates.

IMPROVEMENT OF USING CRUDE EXTRACT UREASE FROM WATERMELON SEEDS FOR BIOCEMENTATION TECHNOLOGY

In recent years,the formation of artificial beachrock and bio-cementation method has gained considerable attention as a sustainable alternative tool in the area of geotechnical and geo-environmental engineering field for soil improvement and construction materials. In general, earlier methods of soil improvement were mostly concentrated on microbes (Bacteria, Fungi, etc.) as a source of urease enzyme widely known as MICP method (Microbial Induced Carbonate Precipitation). To address some of the keylimitations of MICP method this study focused on using crude enzyme (low cost, eco-friendly). Crude enzyme was extracted from watermelon seeds (Citrullus lanatus)considered as “food waste material” and the carbonate formation process known as EICP “Enzyme Induced Carbonate Precipitation.” Crushed and blended watermelon seeds (both dry and germinated) used as a source of urease enzyme. Subsequently, their urease activity was also investigated with various environmental parameters (Temperature, pH, etc.) and investigated the carbonate precipitation trend using calcium chloride (CaCl2) and urea [(CO(NH2)2]. The form of carbonate (calcite, aragonite, vaterite, etc.) was also confirmed by XRD and SEM-EDX analysis. Finally, syringe (d = 2.3 cm, h = 7.1 cm) sand solidification test was conducted using commercially available “Mikawa sand” (mean diameter, D50 = 870 mm) and successfully achieved unconfined compressive strength (UCS) of about 1.2 MPa at neutral pH (~7) and temperature condition (30 °C) considering various curing days and conditions. This study could be useful as an eco-friendly and sustainable method for numerous bio-geotechnical applications (for instance, ground improvement, liquefaction mitigation, artificial beach rock formations, coastal erosion protection, etc.) and the extracted crude urease from watermelon seeds could play as an alternative to replace commercially available urease for carbonate precipitation.

İNŞAAT MÜHENDİSLİĞİNDE ZAYIF ZEMİNLER VE ZEMİN İYİLEŞTİRME YÖNTEMLERİ

In this article, focuses on weak soils and soil all previous studies on weak soils and soil improvements in civil engineering.  For this purpose all academic studies conducted  in the past were scanned, relevant ones were compiled  and it was tried to understand how to determine the most appropriate and most efficient method in improvement. The weakest feature of the soils reveals itself in its bearing capacity. İt is understood from the increase of academic studies publıshed in resent years that different additives are added to these weak soıls under laboratory conditions and there is a search improving the geotechnical parameters of this soıls. It has been understood that the addition of fly ash to a weak and clayey ground and keeping this ground in the appropriate curing time is an effective method for soil improvement since it increases the bearing capacity of the weak ground, and this additive material can give the highest strength by keeping it for the most appropriate curing time. In addition, it has been revealed by experimental studies that the addition of different additives (cement, polymer, garbage water) in appropriate proportions on a sandy or silty weak ground increases the strength of the soil and its resistance to fluidity. Likewise, subjecting a weak ground to consolidation by compressing it with the optimum water content by the compaction method will result in a decrease in the void ratio and naturally increase in the bearing power. The results obtained as a result of all these experimental applications should be evaluated among the soil improvement methods. For this reason based on the soıl improvement methods in all this studies, a remerkable and aplıcable comon starting poınt was trıed to be determined under the tıtle of this article and the methods in the literature studies were associated with the suggestıon from this article.

Unsaturated hydraulic conductivity of compacted bio-cemented lateritic soil in municipal solid waste containment application

Most engineering infrastructures, including municipal solid waste containment facilities, are situated in unsaturated zone. The use of chemical additives for soil improvement has been linked to the adverse environmental issues being experienced globally. Research into more sustainable methods of soil improvement has led to the discovery of a novel and innovative method known as microbial induced calcite precipitation (MICP). Lateritic soil was treated with stepped Sporosarcina pasteurii (S. pasteurii) suspension density up to 2.40 x 109 cells/ml at moulding water content (MWC) -2, 0 and +2 % relative to optimum moisture content (OMC) before compaction using Reduced British Standard light (RBSL), British Standard light (BSL), West African Standard (WAS) or Intermediate and British Standard heavy (BSH) energies. Compacted specimens were saturated with cementation reagent in three cycles with 1/3rd pore volume at 6 hours’ interval to induce calcite precipitation at an ambient laboratory temperature of 24±2°C. The soil-water characteristics curves (SWCC) of the specimens were determined using pressure plate extractor over a pressure range of 10-1500 kPa. Unsaturated hydraulic conductivity values were predicted for the S. pasteurii suspension densities considered using Brooks-Corey, van Genuchten as well as Fredlund and Xing curve fitting prediction models. Results show that the unsaturated hydraulic conductivity values of specimens prepared at lower, MWC relative to OMC were generally higher than at higher MWC regardless of compactive efforts and S. pasteurii suspension densities considered. The Brooks-Corey model gave the best predicted unsaturated hydraulic conductivity values which fit the requirements for waste containment facilities over the matric suction range and S. pasteurii suspension densities considered, than the van Genuchten and Fredlund – Xing, when compared with measured values.

Review on engineering properties of MICP-treated soils

Microbial induced calcium carbonate precipitation (MICP), a sustainable and effective soil improvement method, has experienced a burgeoning development in recent years. It is a bio-mediated method that uses the metabolic process of bacteria to cause CaCO3 precipitation in the pore space of the soil. This technique has a large potential in the geotechnical engineering field to enhance soil properties, including mitigation of liquefaction, control of suffusion, etc. Multi-scale studies, from microstructure investigations (microscopic imaging and related rising techniques at micron-scale), to macroscopic tests (lab-based physical, chemical and mechanical tests from centimeter to meter), to in-situ trials (kilometers), have been done to study the mechanisms and efficiency of MICP. In this article, results obtained in recent years from various testing methods (conventional tests including unconfined compression tests, triaxial and oedometric tests, centrifuge tests, shear wave velocity and permeability measurements, as well as microscopic imaging) were selected, presented, analyzed and summarized, in order to be used as reference for future studies. Though results obtained in various studies are rather scattered, owning to the different experimental conditions, general conclusions can be given: when the CaCO3 content (CCC) increases, the unconfined compression strength increases (up to 1.4 MPa for CCC=5%) as well as the shear wave velocity (more than 1-fold increase in V_s for each 1% CaCO3 precipitated), and the permeability decreases (with a drop limited to less than 3 orders of magnitude). Concerning the mechanical behavior of MICP treated soil, an increase in the peak properties, an indefinite increase in friction angle and a large increase in cohesion were obtained. When the soil was subjected to cyclic/dynamic loadings, lower pore pressure generation, reduced strains, and increasing number of cycles to reach liquefaction were concluded. It is important to note that the formation of CaCO3 results in an increase in the dry density of the samples, which adds to the bonding of particles and may play a major part in the improvement of the mechanical properties of soil, such as peak maximum deviator, resistance to liquefaction, etc.

Methods for mitigating effects induced by tunnelling on nearby existing buildings in cities

Tunnelling in urban areas in soft soil conditions has risks of negative impacts on nearby existing buildings. When buildings are in/on influence zones induced by tunnelling, they can be damaged in the case of without any mitigating methods applied. This paper summarizes and presents a three category classification of mitigating effects induced by tunneling including methods in tunnel design and tunnelling process, and soil improvement methods, as well as reinforcement for buildings. On the basis of the study, designers and engineers can obtain suitable solutions for their safe tunnel projects.

Analytical methods for stress transfer efficacy in the piled embankment

Soft soil reinforced by rigid inclusions under embankment is a soft soil improvement method, known as a piled embankment. It has been widely studied and applied over the world, since 90’s decade of the last century. The behavior of a piled embankment is mainly based on the formation of soil arching within the embankment and the negative skin friction around inclusion shaft. The paper investigates the mechanical behavior of a piled embankment to make clear the load transfer mechanism of the method. Additionally, some of the analytical methods in determining the stress transfer efficacy are presented.

Reinforcing of Sand With 3D Printed Fibres – Review of Properties, Fabrication of Fibres and Initial Testing Programme

Fibre reinforcement is an effective method of soil improvement that presents an alternative solution to other more common methods of ground reinforcement, such as mechanical stabilization by geosynthetics (geogrids, geotextiles, geocomposites, etc.). Research activities in this area are being carried out, but the main disadvantage of currently used fibres is their uniform cross-section and usually smooth surface given by available production methods. This study presents an alternative way of fabrication of synthetic fibres – utilization of fused deposition modelling (3D printing). With the rapid development in commercially available 3D printing techniques, it is now possible to refine the shape and dimensions of the 3D printed objects to a tenth of a millimetre. The review of the basic index and mechanical properties of fibre-reinforced soils is presented in the first part of the paper. The second part is devoted to the description of the production process of fibres including the suitability analysis of materials used for 3D printing. Finally, the initial testing programme of fibre-reinforced non-cohesive soil is presented. The preformed laboratory test confirmed that the inclusion of 3D printed fibres led to a significant increase in shear strength. Examination of samples after tests did not reveal breakage of fibres, thus the fibres pull-out was the governing failure mode.

LABORATORY AND STATISTICAL EVALUATION OF CEMENT AND LIME ON THE PROPERTIES OF TROPICAL BLACK CLAY – IRON ORE TAILINGS MIXTURES

The need for cheaper and more economical soil improvement methods is of great significance in order to reduce the construction cost of flexible pavements. Also, major problems caused by industrial waste in Nigeria can be minimised by recycling or re-using of such wastes for soil improvement. The application of cement and lime along for such purpose has proven to increase the construction cost. Thus the use of industrial waste such as iron ore tailings (IOT) could aid in reducing the construction cost. Series of laboratory and statistical investigations were performed to compare the effect of cement and lime on the properties of tropical black clay (i.e. black cotton soil, BCS). Soil samples were admixed with up to 10 % IOT content and modified with up to 4 % each of cement and lime by dry weight of soil to evaluate their plasticity and compaction characteristics. Compaction was done with British Standard light (BSL) energy. Statistical tests for regression and correlation was achieved using Mini-tab R15 and Microsoft Excel software correspondingly. Results disclosed decreased in liquid limit and plastic limit. Liquid limit values of 56, 54.8, 54.5, 52.5, 52 and 51% were noted for 0, 2, 4, 6, 8 and 10% IOT content. Similar trend was noted for 1, 2, 3 and 4% lime and cement concentrations. A rise in maximum dry density (MDD) and drop in optimum moisture content (OMC) with greater concentration of IOT for all the lime and cement contents under study was noted. Statistical analysis revealed that soil-lime-IOT mixtures gave higher predicted values than soil-cement-IOT mixture for determining plasticity and compaction characteristics of BCS – IOT mixtures. Thus, 4 % lime – 6 % IOT mixture met the criteria for flexible pavement purpose as proposed by Nigerian General Specifications and is recommended for used as pavement material for roads that are lightly trafficked. While the soil – cement - IOT mixes fell to meet the criteria for used as pavement material.