Shear Strength Of Sandy Soils Research Articles

Experimental Study of Cationic-Modified Biopolymer for Increasing the Shear Strength of Sand

The application of biopolymers as a more environmentally friendly alternative to cement has emerged as an interesting research subject.The purpose is to enhance the shear strength of sandy soils. In this article, the selected biopolymer is cationic-modified starch. It is expected that cationic starch will have less water absorption properties since modified starch has cationic groups in place of the OH- groups found in the normal starch. This cationic-modified starch namely Amylofax. Five types of samples are created for this testing, including Sample A is prepared with the composition of (silica sand + 2% Amylofax T1100 (w/w) + 20% water (w/w))., Sample B consists of (silica sand + 2% Amylofax T2200 (w/w) + 20% water (w/w))., Sample C is comprised of (silica sand + 2% Amylofax T1100 (w/w) + 2% Glucomannan (w/w) + 20% water (w/w)), Sample D consists of (silica sand + 2% Amylofax T2200 (w/w) + 2% Glucomannan (w/w) + 20% water (w/w)), and Sample E includes (Ottawa sand + 2% cement (w/w) + 20% water (w/w)). The samples were tested using a direct shear test apparatus to determine the soil shear strength parameters (c) cohesion and (Ø) internal friction angle. After conducting the tests on the sand samples with the addition of modified starch biopolymer (cationic starch), it was found that the cohesion value was 961kPa, and the internal friction angle was 63°. These results indicate higher shear strength values compared to sand mixed with natural starch.

Prediction of yield shear strength of saturated sandy soils using artificial neural networks

ABSTRACT The undrained shear strength of sandy soils during flow failures and liquefaction is a critical metric in the analysis of undrained stability. In our study, the numerical technique known as Artificial Neural Network (ANN) is used for simulating the triaxial stress–strain relationship of sandy soils. This paper aims to predict the undrained shear strength of saturated sandy soil. The proposed program requires simple laboratory soil data to proceed. They are median grain diameter (D50), fines content percentage (FC%), void ratios and relative density. In addition, the stress data of undrained loading such as effective vertical stress (σ’1) and effective horizontal stress (σ’3) are needed. Then, using the program, the deviator stress at yield (qu yield) and, consequently, the yield shear strength of sandy soil (Su (yield)) can be determined. A database of experimental undrained triaxial of saturated sandy soils was collected from the literature and prepared to be the inputs of the network. Two artificial neural networks have been built. By comparing the effectiveness of the two networks, the Back Propagation Neural Network (PBNN) approved higher results and more accuracy than the General Regression Neural Network (GRNN). The computer program, yield shear strength prediction application, written in visual basic, has been developed by the author. For model validation, seven case studies (seven patterns of the production set), which were not seen by the network previously, were presented to the application and the results are compared to the actual output. The produced yield shear strength is very close to the actual strength.

Optimization of calcium carbonate precipitation during alpha-amylase enzyme-induced calcite precipitation (EICP).

The sand production during oil and gas extraction poses a severe challenge to the oil and gas companies as it causes erosion of pipelines and valves, damages the pumps, and ultimately decreases production. There are several solutions implemented to contain sand production including chemical and mechanical means. In recent times, extensive work has been done in geotechnical engineering on the application of enzyme-induced calcite precipitation (EICP) techniques for consolidating and increasing the shear strength of sandy soil. In this technique, calcite is precipitated in the loose sand through enzymatic activity to provide stiffness and strength to the loose sand. In this research, we investigated the process of EICP using a new enzyme named alpha-amylase. Different parameters were investigated to get the maximum calcite precipitation. The investigated parameters include enzyme concentration, enzyme volume, calcium chloride (CaCl2) concentration, temperature, the synergistic impact of magnesium chloride (MgCl2) and CaCl2, Xanthan Gum, and solution pH. The generated precipitate characteristics were evaluated using a variety of methods, including Thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). It was observed that the pH, temperature, and concentrations of salts significantly impact the precipitation. The precipitation was observed to be enzyme concentration-dependent and increase with an increase in enzyme concentration as long as a high salt concentration was available. Adding more volume of enzyme brought a slight change in precipitation% due to excessive enzymes with little or no substrate available. The optimum precipitation (87%) was yielded at 12 pH and with 2.5g/L of Xanthan Gum as a stabilizer at a temperature of 75°C. The synergistic effect of both CaCl2 and MgCl2 yielded the highest CaCO3 precipitation (32.2%) at (0.6:0.4) molar ratio. The findings of this research exhibited the significant advantages and insights of alpha-amylase enzyme in EICP, enabling further investigation of two precipitation mechanisms (calcite precipitation and dolomite precipitation).

The behaviour of stress variation in sandy soil

Abstract This research article represents the recompacted dense sand sample behaviour and stress distribution in the direct shear box. In Lithuania, sand is quite common on a construction site, in general about 32%. To reduce the influence of the shear box design on the experimentally determined values of the soil strength parameters, it is necessary to know the regularities of the change of the normal load acting in the shear plane. Three different normal stresses of 50, 100, and 200 kPa were applied to the dense sand in the direct shear boxes during experimental and numerical simulation. The results showed an obvious evidence of non-uniformity of stress for standard and raised specimens. The numerical analysis exhibited that when the sample is loaded only with a vertical load, approximately 75% of that load is transferred to the sample bottom, 84% to the shear plane, and 95% to the top. At the end of the shear test, the vertical force in the shear plane reaches maximum, the normal stress is higher by 13.5% than applied on the sample top. The shear strength of sandy soils were influenced by box size and sample height too. The improved shear box apparatus allows to estimate the vertical load at shear plane.

Contribution of root tensile of Pennisetum polystachion on shear strength of sandy soil in slope bio-engineering technique

Aim: In soil bio-engineering, plant has been widely adopted as important material in promoting sustainable ecological function in slope instability measures. Plant canopy provides shelter and at subsurface level, root networking attributes toward stability of soil against erosion and slope failure. To investigate the potential of selected P. polystachion as biological material in soil bio-engineering for improving the soil shear strength of sandy soil planted with P. polystachion. Methodology: The selected species was initially planted using hyroseeding technique on studied plots which facilated with and without fiber netting (made of paddy straw). A control plot was also prepared for reference of this study. The plots were routinely watered twice a day for six months before experimental program was scheduled for determining of root tensile and soil shear strength tests. Results: The root tensile strength of P. polystachion exhibited a positive significant relationship between root tensile force and root diameter. The shear strength of soil was affected by the presence of root if compared to that of soil without root (control). Biomass analysist also agree with the soil water content, ws. High biomass contributed to the increase in the values of soil shear strength parameter of cohesive, c and angle of friction, q for root-permeated soil with P. polystachion. Interpretation: This study has suggested that the potential application of this selected species for slope vegetation in improving the erosion control and slope stability in soil-bioengineering scheme.

Influence of silt content on shear strength of sandy soil

Direct shear tests were carried out on silt standard sand specimens with four silt contents of 0%, 5%, 10%, 20% under three conditions of average maximum dry density, optimal moisture content and saturation, respectively. The effects of different contents and different states on internal friction angle and cohesion of sand specimens were studied. It is found that the internal friction angle and cohesion increase with the increase of silt content under the condition of average maximum dry density and optimal water content, and with the increase of silt content, the internal friction angle decreases and the cohesion increases in saturated state.

Anisotropic Behavior of Cohesive Soils by Considering Effect of Gradation and Plasticity Characteristics

In practice, strength of soils commonly is measured isotropically, while for accurate design of structure foundations and earth structures, it is essential to consider the effect of anisotropy phenomenon on the mechanical behavior of the soils. In previous research, the effect of anisotropy on shear strength of sandy soils has been known and there is some limited work on cohesive soil. Moreover, anisotropy impact is not known on shear-induced pore water pressure. In this research, a series of triaxial tests were carried out on the undisturbed samples of different fine-grained soils, taken at different directions in the sites. The samples were consolidated under effective isotropic stresses of 200, 300, 500 and 700 kPa, and loaded in undrained condition. The results revealed that the behavior of all soils significantly depends on the sample orientation in the field. As the direction of samples changed from “perpendicular to bedding orientation” to “parallel to bedding orientation”, the shear strength decreased gradually and it has the minimum value at anisotropy angle of 72°, 59° and 90° for red clay, yellow marl and olive marl, respectively. The reduction rate completely depends on the soil plasticity and level of confining pressure.

Liquefied Strength Ratio for Eight Laboratory-Tested Sandy Soils

AbstractUse of a liquefied strength ratio to estimate strengths for postliquefaction slope stability analyses assumes that the liquefied shear strength of sandy soil can be normalized by the consol...

Review of Enzyme-Induced Calcite Precipitation as a Ground-Improvement Technique

Calcite-induced precipitation methods (CIPMs) have recently become potential techniques in geotechnical engineering for improving the shear strength of sandy soil. One of the most promising methods among them is enzyme-induced calcite precipitation (EICP). In this technique, a mixed solution composed of reagents and the urease enzyme, which produces calcite, is utilized as the grouting material. The precipitated calcite in granular soil provides ties among the grains of soil and limits their mobility, thus promoting an improvement in strength and stiffness and also a reduction in the hydraulic conductivity of sandy soil. This paper discusses the potential increase in the strength and stiffness of the soil, the additional materials for grouting, the effect of these materials on the treatment process, and the engineering properties of the soil. The possible sources of the urease enzyme and the applicability of the EICP method to other soil types are also discussed in this paper. The environmental and economic impacts of the application of EICP are also presented. The envisioned plans for application, potential advantages, and limitations of EICP for soil stabilization are discussed. Finally, the primary challenges and opportunities for development in future research are briefly addressed.

Experimental and Numerical Investigation of Internal Erosion Effect on Shear Strength of Sandy Soils

Internal erosion is a complex process which is considered as the main cause of hydraulic works failure. It involves detachment and transportation of fine particles from the soil matrix, due to seepage flow. The susceptibility of dikes and dams to internal erosion has been widely investigated. However, its effect on soil shear resistance characteristics was less reported. This study presents an experimental and numerical investigation of internal erosion effect on the shear strength of sandy soils. In the first step, direct shear tests without erosion were carried out on sandy soils made of sand mixed with three types of fine particles at different contents (10%, 15%, 20%). In the second step, sequential erosion-shear tests were conducted using a modified shear box that permits seepage through compacted specimens and allows collection of effluent with eroded particles for further evaluation of the effect of extended internal erosion on soil shear strength. The results showed that the finer the mixture, the more its cohesion is altered by erosion. So, after erosion, both cohesion and internal friction angle decreased for the different fines contents tested. A numerical model based on porosity diffusion law was used to simulate the soil strength alteration due to suffusion, and comparison between experimental and numerical results indicated a quite good agreement for cohesion reduction. Sequential erosion-shear tests carried out on different mixtures have shown that internal erosion affects shear strength characteristics and can lead to the instability of soil slopes, dikes, dams and flood protections.

Effects of granulated waste glass and micro steel fiber on shear strength parameters of sand

During the construction of the various structures, soil strength plays a vital role in structural performance. Hence, soil improvement techniques are needed to improve soil strength as well. This study aimed to improve shear strength of sandy soil using Granulated waste glass (GWG) and Micro steel fiber (MSF). In order to apply this idea, there have been taken two kinds of sandy soil such as fine sand (locally available in Kushtia) and coarse sand (locally available in Domar). As for basic properties of sand, fineness modulus, specific gravity, maximum dry density, etc. are determined from experimental results. After grounding the waste glasses into granulated form and cutting the 0.70 mm steel wire into a uniform size of 10 mm in length, the GWG and MSF have been mixed in the sand by various proportions namely 5%, 10% and 15% by weight. The observation on the soil improvement technique which is adopted in this paper is summarized that the cohesion of the Kushtia sand is increased up to 1376.7% for 10% MSF and angle of internal friction is increased up to 8.7% for 10% GWG. The cohesion of the Domar sand is increased up to 1877.5% for 10% MSF and angle of internal friction is increased up to 24.4% for 15% MSF. Therefore, it can be concluded that the shear strength becomes increase for both sand up to optimum content using the considered percentage of GWG and/or MSF.

Performance of Sand Reinforced with White Coir Fibre

Coconut fibre or more commonly known as coir fibre is obtained from the outer shell of coconut. The production of coconut in Malaysia is the fourth important industrial crop after oil palm, rubber and paddy field. However, wastes generated by the coconut are almost fully utilised as by-products and reinforcing material for soil. In fact, the availability of the coconut waste in Malaysia makes it suitable for soil reinforcing material purposes. Problem that sometimes occurs is to dispose this big, heavy and hard coconut at landfill area. It may require more space to go through landfill method. Disposal of this waste material is vital as it can affect the environment. Therefore, by using part of the coconut component can help to overcome this problem. In this research, white coir fibre was utilized as the reinforcing material to sandy soil to suit the backfill material for earth retaining structure that is related to road infrastructure. The lengths of the white coir fibre were fixed at some length according to its orientation such as random, vertical and horizontal. Shear strength parameter were tested using Direct Shear Test. In this research, inclusion of white coir fibre in sandy soil shows enhancement of the shear strength parameter such internal friction angle of soil regardless of its orientation. However, there is no clear relationship between the effect of white coir fibres orientations to the shear strength of sandy soil.

Evaluation of Shear Strength Parameters of Sandy Soils upon Microbial Treatment

ABSTRACTA new method for soil stabilization known as microbial-induced calcite precipitation (MICP) has been the focus of research in this area during the last decade. In this method, the reaction of microorganisms in the presence of urea and calcium chloride is used to produce calcite. Despite the large numbers of bacteria in soil, Sporobacillus pasteurii (previously known as Bacillus pasteurii) has the most capability to create cementation between soil particles in the MICP method due to its high urease activity. In this paper, the effect of MICP treatment on the shear strength characteristics of a sandy soil was studied. The change in the shear strength of sandy soil upon MICP treatment was measured using a strain-controlled direct shear test before and after treatment of the soil samples. The results showed an increase of 44–86% in the shear strength of the sandy soil after 15 days of MICP treatment compared to the untreated soil. The enhanced shear strength was the result of an increase in both the cohesion intercept and angle of internal friction. The increase in the cohesion intercept was more significant than the increase in the angle of internal friction.

Studies on Improvement of Shear Strength of Sandy Soil using Egg Shell Powder and Quarry Dust

Studies on Improvement of Shear Strength of Sandy Soil using Egg Shell Powder and Quarry Dust

Effect of Geotextile Reinforcement on Shear Strength of Sandy Soil: Laboratory Study

Abstract This paper presents results of a series of undrained monotonic compression tests on loose sand reinforced with geotextile mainly to study the effect of confining stress on the mechanical behaviour of geotextile reinforced sand. The triaxial tests were performed on reconstituted specimens of dry natural sand prepared at loose relative density (Dr = 30%) with and without geotextile layers and consolidated to three levels of confining pressures 50, 100 and 200 kPa, where different numbers and different arrangements of reinforcement layers were placed at different heights of the specimens (0, 1 and 2 layers). The behaviour of test specimens was presented and discussed. Test results showed that geotextile inclusion improves the mechanical behaviour of sand, a significant increase in the shear strength and cohesion value is obtained by adding up layers of reinforcement. Also, the results indicate that the strength ratio is more pronounced for samples which were subjected to low value of confining pressure. The obtained results reveal that high value of confining pressure can restrict the sand shear dilatancy and the more effect of reinforcement efficiently.

Improvement of Shear Strength of Sandy Soil by Cement Grout with Fly Ash

The effects of the permeation cement grout with fly ash on the sandy soil skeleton were studied in the present work in two phase; first phase the shear strength parameters, and the second phase effect of these grouted materials on volume grouted zone by injection (51) cm³ of slurry in sandy soil placed in steel cylinder model with dimension 15 cm in diameter and 30 cm in height. The soil sample was obtained from Karbala city and it is classified as poorly graded sand (SP) according to USCS. The soil samples were improved by cement grout with three percentages weight of water cement ratio (w:c); (0.1w:0.9c, 0.8w:0.2c, and 0.7w:0.3c), while the soil samples were dehydrated for one day curing time. Fly ash class (F) was used with cement grout as filler material; it was added to the mixture as a replacement material for cement in weight percentages; 10%, 25% and 40%. According to the results of tests, both shear strength and approximate volume of the effective grouted zone for treated samples soil with cement grout was increased when the water cement ratio decreased. Fly ash with cement grout needs to increase the water demand for the grout mixing to give best results in both shear strength and filling the soil voids.
 

갭 입도 변화에 따른 사질토의 지지력 향상 효과

갭 입도 변화에 따른 사질토의 지지력 향상 효과

Kuat Geser Tanah Pasir yang Distabilisasi Menggunakan Aspal Cair SC60-70

Soil is one of the most important parts in construction work. Soil being found in the field are vary in terms of its properties, and its quality usually does not meet the specified requirements for building construction on it including sandy soil. Sandy soil does not have cohesion value (c), so its shear strength is very low and can lead to collapse. Because of that, it needs to be stabilized to improve the parameter of soil shear strength which are friction angle value (φ) and cohesion value (c). Stabilizing material being used in this research is asphalt, in order to improve cohesion and soil density. Asphalt being used in this research is emulsified asphalt SC 60-70 which is Asphalt Cement (AC) dissolved in diesel oil. In this research, the shear-strength of sandy soil stabilized with emulsified asphalt SC 60-70 was analyzed by means of direct shear-strength testing. It can be concluded from the result that friction angle tends to increase with the increase of the asphalt content. It can also be shown that the lowest friction angle value was found being at 0% asphalt content, 35,753°, while the biggest friction angle value was found being at 5% asphalt content, 38,970° (increased 10,169%).

Shear Behavior of Sand–Silt Mixtures: A Laboratory Investigation of Coastal Silty Sand Soils of Mostaganem

In recent years, interest in understanding the mechanisms of mechanical instability of porous media, leading to catastrophic failure has been continuously revised to include, new porous media parameters generating the phenomenon of liquefaction under static or dynamic loadings. Results from experimental test programs have concluded too many physical concepts based on material intrinsic properties, initial states, and other characteristics. Despite the great progress on the subject, these concepts do not allow a unified treatment of such porous media. The assessment of critical shear strength of sandy soils as porous media under undrained conditions is a major challenge in stability analysis. Such strength serves to evaluate the occurrence of flow deformation under liquefaction phenomena. The determination of the critical undrained strength is essentially fundamental for the design of soil structures such as earth dams, bridge supports, building foundations as well as soil densification process to avoid catastrophic failure due to soil instability manifested by failure or large displacement such as settlement. In this work, experimental program on reconstituted loose and medium dense specimens of terrigenous silica sands with different specified fine contents was carried out to analyze its mechanical behavior under undrained conditions. The present article is an attempt to experimentally describe mechanical behavior and theoretically justify such response of loose and medium dense sand by means of critical state soil parameters.

Undrained Static Response of Loose and Medium Dense Silty Sand of Mostaganem (Northern Algeria)

Critical undrained shear strength of sandy soils is a fundamental parameter in stability analysis. This will help to evaluate the occurrence of flow deformation under liquefaction phenomena. A precise evaluation of the undrained liquefaction strength is very important for the design of soil structures such as earth dams, building foundations and soil densification process which can avoid catastrophic failure due to soil instability. In this work, laboratory investigation on natural and on reconstituted soil specimens of silica sands was carried out to enable the analysis of its mechanical behavior. Several concepts have been proposed by many researchers in order to characterize instability of silty sands. However, a review of studies published in the literature indicates that no clear conclusions can be drawn as to what manner the variation of fine content affects the mechanical behavior. The present paper is an attempt to experimentally describe mechanical behavior and theoretically justify such response of loose and medium dense sand by means of critical state parameters. Two distinct stress path tendencies have been shown in this study. In undrained conditions, loose samples show amplified contractive phase with fine content ranging from 0 to 30%, while medium dense samples exhibit a contractive phase followed by a dilative phase with fine contents beyond 30%. In this study, it has been shown that the strength of sand fabric of carrying loads becomes weaker and the critical state parameter increases with the increase in fine content leading to the reduction of normalized critical undrained shear strength.