Results Of Unconfined Compression Tests Research Articles

Experimental Study on Optimization of Consolidation Parameters of Silty Clay Based on Response Surface Methodology: A Case Study on the Protection and Restoration of the Ming and Qing Dynasty Hangzhou Seawall Site

The preservation of the ancient seawall site is a focal point and challenge in the protection of historical relics along Hangzhou’s Grand Canal in China. This endeavor holds significant historical and contemporary value in uncovering and perpetuating Hangzhou’s cultural heritage. Researchers investigating the Linping section of the seawall site aimed to address soil site deterioration by selecting environmentally friendly alkali-activated slag cementitious materials and applying the response surface method (RSM) to conduct solidification experiments on the seawall soil. Researchers used the results of unconfined compressive strength tests and microscopic electron microscopy analysis, considering the comprehensive performance of soil solidification mechanisms and mechanical properties, to establish a least-squares regression fitting model to optimize the solidification material process parameters. The experimental results indicate that the optimal mass ratio of lime, gypsum, and slag for achieving the best solidification process parameters for the seawall soil, with a 28-day curing period, is 1:1.9:6.2. This ratio was subsequently applied to the restoration and reconstruction of the seawall site, with parts of the restored seawall exhibited in a museum to promote the sustainable conservation of urban cultural heritage. This study provides theoretical support and practical guidance for the protection and restoration of soil sites.

Experimental investigation on static and dynamic properties of nanosilica modified cement soil

It has been proved that nanosilica can improve the mechanical properties of cement soil, however, the static and dynamic properties of nanosilica modified cement soil and dispersion method study of nanosilica in cement soil were few, thereby investigated by unconfined compression test and dynamic triaxial test in this study. A series of unconfined compression test results indicated that the dispersion method of nanosilica is of importance in the strength of nanosilica modified cement soil (NCS), and soaking in water for 24 h is the optimal dispersion method among designed methods. Unconfined compressive strength (UCS) increases with increasing nanosilica content in the range of 0 to 0.4%, and then reduces gradually while nanosilica content is beyond 0.4%. The optimal nanosilica content can be seen as 0.4%, and the corresponding UCS at the curing age of 7 d is 960 kPa, which increases by 47.2% comparing to the specimen without nanosilica. Dynamic triaxial test reveals that the variation of the cumulative plastic axial strain and dynamic elastic modulus versus nanosilica content are same and opposite to UCS respectively, and the minimum of the cumulative plastic axial strain and maximum of dynamic elastic modulus are obtained while nanosilica content is 0.4%, which reduces by 48.1% and increases by 69.8% respectively comparing to the specimen without nanosilica. Finally, a simple and practical prediction model is developed to capture the evolution of the cumulative plastic axial strain with cycle number, and its simulation effect is validated by dynamic triaxial test results. It is believed that this paper finds an efficient dispersion method of nanosilica in cement soil, and provides the dynamic properties of nanosilica modified cement soil, which can promote practical application of nanosilica in road engineering.

Effects of metakaolin and sodium silicate treatment on highwater content dredged clay for improved construction fill performance

This study experimentally investigated the strength characteristics of metakaolin (MK) and sodium silicate (SS) treated dredged clay at high water content for use as construction fills. A series of laboratory tests including direct shear tests, unconfined compression tests, SEM and XRD tests were carried out to systematically evaluate the effects of water content, sodium silicate modulus, curing agent content, and curing time on the strength behavior of MK and SS treated dredged clay samples. The direct shear test results showed that the shear strength at a given vertical stress consistently increases with the increase of curing agent content and curing time while decreasing with the modulus of SS. Both cohesion and friction angle increase with increasing curing agent content and curing time, while reducing with the increasing modulus of SS. Unconfined compression test results showed that all samples tested exhibit a strain-softening behavior. The value of unconfined compressive strength increases with the increase of curing agent content and curing time but decreases with the increase of water content and modulus of SS. The optimal dosage combination is a sodium silicate modulus of 0.9, curing agent content of 12%, and curing time of 28d. SEM test confirmed the formation of gels in the treated soil sample, the dredged clay showed a more uniform and denser microstructure after treatment. Through XRD analysis, it is not easy to generate direct chemical reactions with no new mineral components generated in the sample. For high-water content dredged clay, it is recommended to use an optimum dosage combination of MK and SS to achieve a better treatment effect for use as construction fills.

Study on Mechanical Performance and Reinforcement Mechanisms of Geocell-Reinforced Soil

A concept for a reinforcement mechanism is presented and analyzed combined with test results to explain the reinforcement effect of a geocell. A series of pull-out and unconfined compression tests were carried out to investigate the effect of various parameters, including water content, compactness, and the number of geocell-reinforced layers, on the mechanical performance of geocell-reinforced soil. The results of the pull-out tests were mutually verified by the formulas for the reinforcement mechanism and demonstrate that the compactness and water content significantly affect the friction coefficient of the geocell–soil interface, which increases as compactness rises and water content falls. Compared with lowering the water content, improving compactness was better for enhancing the frictional properties of the geocell–soil interface; this had the highest increase, at 90%, as compactness rises from 92% to 94%. According to the unconfined compression test results, the unconfined compressive strength of geocell-reinforced soil is raised by higher compactness, more geocell-reinforced layers, and lower water content; this had the highest increase, at 93.1%, as the water content dropped to its optimum, from 19% to 15%. The compactness of filled soil dramatically influences the unconfined compressive strength of unreinforced specimens, which had an increase of 59.6% when compactness rose from 92% to 94%. However, this effect was weakened as more geocell was added to filled soil. As the number of geocell-reinforced layers rose from 0 to 1 under the compactness level of 92%, the increase of ultimate unconfined compressive strength reached 82.6%, higher than in other reinforcement layers.

Bearing Capacity of Shallow Foundations on Unsaturated Silty Soils

In general, the ultimate bearing capacity (UBC) of shallow foundations on unsaturated soils is characterized by the conventional shear strength (SS) parameters in which saturated theories are applied. However, in this case, it is clear that the foundations designed using the obtained values from the saturated cases not be economical. In recent years, procedures have been developed to estimate the UBC of foundations on unsaturated soils, that take into account drained and undrained loading conditions. However, these studies generally concentrate on sandy soils. The validity of the results proposed in the literature should be tested for other soils. Therefore, this paper includes a conventional direct shear box (DSB) test to determine the unsaturated SS of statically compacted silty soil, and a series of model tests were performed to determine the foundation’s UBC. In the experimental model setup, the UBC values of different types and sizes of model foundations on silty soil layers with a different soil saturation degrees (SSDs)/matric suctions (MSs) and different void ratio values were measured. In addition, the soil-water characteristic curves (SWCCs) and SS parameters of unsaturated silt were obtained. Using the experimental results, a new equation is proposed for the characterization of the UBC of shallow foundations on unsaturated silty soils. Using this equation, the UBC of unsaturated soils can be determined based on the results of unconfined compressive strength tests (UC) measured on unsaturated soil samples and based on the degree of saturation and the fitting parameter. The results indicate that the measured bearing capacity values obtained via the model footing test, shows a good consistency with those obtained by the proposed equation.

Experimental study on strength characteristics and internal mineral changes of Lime-stabilized loess under High-Temperature

• Effect of lime treatment on compression and shear strength of loess were studied. • Tests were carried out at a wide temperature range (30 ∼ 300 °C) and 5 lime contents. • Treatment with lime improved the strength of loess at high-temperatures. • Multiple methods XRD, TGA, DSC reveal the mechanisms of the lime-loess reactions. In this study, lime-stabilized loess with five lime contents (0 %, 3.5 %, 7 %, 10.5 %, and 14 %) treated at four temperature levels (30 °C, 100 °C, 200 °C, and 300 °C) were tested for 48 h in a series of laboratory experiments to investigate the mechanical strength characteristics and internal mineral changes of lime-stabilized loess under high temperature. The unconfined compressive strength (UCS) tests and shear box test results show that the compressive and shear strengths of lime-stabilized loess are larger than those of plain loess, not only at room temperature but also at high temperatures. Under the same lime content, the mechanical strength of each sample was greatly improved after high-temperature treatment. As the heat-treatment temperature increased within the test temperature range, the compressive and shear strengths gradually improved. These mechanical strength test results prove that adopting lime-stabilized loess as the building material for structures vulnerable to high temperatures is feasible. When compressive and shear strengths were selected as the evaluation criteria for determining the lime content, the optimal lime content in this study was 7 %. X-ray diffraction and thermal analysis test results revealed that the strength enhancement of lime-stabilized loess is mainly derived from the lime slaking reaction, pozzolanic reaction, and crystallization reaction. High-temperature treatments can promote the reaction rates of these processes.

Effect of post-construction moisture condition on mechanical behaviour of Fiber-reinforced-cemented-sand (FRCS)

ABSTRACT Such parameters as cement content, cement type, relative density, grain size distribution, and moisture condition can influence the mechanical behaviors of Fiber-Reinforced-Cemented-Sand (FRCS). Various tests such as Unconfined Compression Strength (UCS), Unconsolidated-Undrained triaxial compression strength (UU), ultrasonic tests, and various analysis, that is, Scanning Electron Microscopy (SEM), image processing, Analysis of Variance (ANOVA), and sensitivity have been performed to investigate the effect of moisture conditions on the mechanical characteristics of treated sandy soil. All the specimens contained 3% or 6% cement contents by dry weight ratio of soil. In addition, kenaf fibers with 8 mm length were utilized by dry weight ratio of 0, 0.25, 0.5 and 0.75 percent; specimens were cured for 14 and 28 days. The results of unconfined compression test demonstrate that both the peak strengths and the residual strengths were decreased by immersing samples and increasing the saturation degree. For instance, for soaked samples with fiber content (FC) of 0.75%, the UCS and residual strength decreases 28% and 40%, respectively. Additionally, the undrained cohesion (Cu) obtained from unconfined compression test declines due to the sample inundation which is directly related to the amount of fiber. In contrast, triaxial test undrained cohesion (Cu) rises by doing so.

Geotechnical characteristics of lateritic clay admixed with biomass silica stabiliser

This paper examines the effectiveness of using varying proportion (2%, 4% and 6% by dry weight of soil) of a newly formulated biomass silica soil stabiliser (BSS) on tropical lateritic clay which has deleterious effects on construction materials due to its high amounts of SiO2 and Fe2O3. A series of laboratory experiment testing methods: i.e. particle size distribution, Atterberg Limits, linear shrinkage, pH value, compaction, California Bearing Ratio, unconfined compression test, and cyclic load triaxial test were conducted in accordance to BS1377:1990 and AASHTO T307–99:2003 to examine the geotechnical properties of the BSS structured lateritic clay subjected to 0, 7, 14 and 28 curing days. Physicochemical tests such as X-ray fluorescence (XRF), X-ray diffraction (XRD) and field-emission scanning electron microscope (FESEM) were conducted to further support the mineralogical composition and microstructure evidence of the structured soil and substantiate the interpretation of the mechanical strength data. The test results reveal that the notable changes in the properties and behavior of structured lateritic clay was governed by the BSS proportion and curing period. There is an immediate enhancement in the geotechnical properties of the 2% BSS structured lateritic clay, altering soil type from CH to MH before curing begin. The unconfined compressive test results indicate a distinct effectiveness in stabilizing lateritic clay, from 400 kPa to 3675 kPa for 6% BSS structured lateritic clay cured to 28 days. Both soaked and unsoaked California Bearing Ratio (CBR) values were 12.4 and 5.8 folds higher than that of the virgin lateritic clay. The cyclic load triaxial test reveals that the resilient modulus, MR of the structured soil was significantly increased. For full-scale applications, the association between the mechanical properties and linear shrinkage test results deduce that the optimum proportion of BSS required for an effective stabilisation performance is 6%. Finally, the mechanisms of the microstructural changes in the stabilisation process were mainly attributed to the agglomeration and aggregation of the cemented particle through composition of calcium silicate hydrate cementitious products evidenced in the physicochemical tests.

Laboratory Study on Improvement of Expansive Soil by Chemically Induced Calcium Carbonate Precipitation

This paper proposes the use of calcium carbonate (CaCO3) precipitation induced by the addition of calcium chloride (CaCl2) and sodium carbonate (Na2CO3) solutions as a procedure to stabilize and improve expansive soil. A set of laboratory tests, including the free swell test, unloaded swelling ratio test, unconfined compression test, direct shear test, scanning electron microscopy (SEM) test, cyclic wetting–drying test and laboratory-scale precipitation model test, were performed under various curing periods to evaluate the performance of the CaCO3 stabilization. It is concluded from the free swell tests and unloaded swelling ratio tests that the addition of CaCl2 and Na2CO3 can profoundly decrease soil expansion potential. The reduction in expansion parameters is primarily attributed to the strong short-term reactions between clay and stabilizers. In addition, the formed cementation precipitation can decrease the water adsorption capacity of the clay surface and then consequently reduce the expansion potential. The results of unconfined compression tests and direct shear strength tests indicated that the addition of CaCl2 and Na2CO3 has a major effect on geotechnical behavior of expansive soils. Based on the SEM analyses, new cementing crystalline phases formatted by sequentially mixing CaCl2 and Na2CO3 solutions into expansive soil were found to appear in the pore space, which results in a much denser microstructure. A laboratory-scale model test was conducted, and results demonstrate the effectiveness of the CaCO3 precipitation technique in stabilizing the expansive soil procedure. The test results indicated that the concentration of CaCl2 higher than 22.0% and Na2CO3 higher than 21.2% are needed to satisfactorily stabilize expansive soil. It is proposed to implement the precipitation technique in the field by the sequential permeation of CaCl2 and Na2CO3 solutions into soils in situ.

Utilizing Alumina-Silica Enriched Bricks Debris Determining End Product of ML-CL Fill Soil: Advanced Stabilization Practices with Innovating Discarded Material

Testing soil and knowing its strength parameters is one of the basic components in construction. Testing of fill soil is carried out to find whether the existing soil can endure the burden of structure withheld upon it or not. In the case of weak soil, one can find it difficult to pursue construction or any development project. While talking of solutions, there are many methods to improve its strength and properties: one of them which we decided to work on is 'stabilization of fill soil using bricks waste which is normally easily available material. The main objective of our test is to check the effectiveness of bricks waste on the mechanical properties of filling material. The testing comprised of performing Atterberg limits, Unconfined Compression, Direct Shear, Sieve Analysis, Moisture Dry Density, and Permeability. The Bricks waste passing no. 40 sieve is mixed with fill soil and testing on different proportions i.e. 0, 5, 10, 15 and 20 percent was carried out. The summary was prepared showed improvement in soil regarding the shear strength and toughness as the Plasticity Index of the soil was improved. The unconfined compression test results show a pattern in which the peak stress is increased as we move to higher percentages. Also, the moisture content is increased for this test because the brick debris absorbed water. Direct shear test on percentages up to 15% showed that the peak shear stress increased, which indicates that on higher percentages the sample took more load as compared to small percentages. Moisture Dry Density relationship provides a clear indication of an increase in density of soil as moved to higher percentages and decrease in Optimum Moisture Content which suggests that, clay absorbs more water content as compared to brick debris.

Unconfined compressive strength prediction of soils stabilized using artificial neural networks and support vector machines

This study aims to improve the unconfined compressive strength of soils using additives as well as by predicting the strength behavior of stabilized soils using two artificial-intelligence-based models. The soils used in this study are stabilized using various combinations of cement, lime, and rice husk ash. To predict the results of unconfined compressive strength tests conducted on soils, a comprehensive laboratory dataset comprising 137 soil specimens treated with different combinations of cement, lime, and rice husk ash is used. Two artificial-intelligence-based models including artificial neural networks and support vector machines are used comparatively to predict the strength characteristics of soils treated with cement, lime, and rice husk ash under different conditions. The suggested models predicted the unconfined compressive strength of soils accurately and can be introduced as reliable predictive models in geotechnical engineering. This study demonstrates the better performance of support vector machines in predicting the strength of the investigated soils compared with artificial neural networks. The type of kernel function used in support vector machine models contributed positively to the performance of the proposed models. Moreover, based on sensitivity analysis results, it is discovered that cement and lime contents impose more prominent effects on the unconfined compressive strength values of the investigated soils compared with the other parameters.

Improvement of Unconfined Compressive Strength of Soft Clay using Microbial Calcite Precipitates

The precipitation of calcite induced via microorganisms (MICP) is a technique that has been developed as an innovative sustainable ground improvement method utilizing ureolytic bacteria to soil strengthening and stabilization. Locally isolated Bacillus Sonorensis from Iraqi soil samples were found to have high abilities in producing urease. This study aims to use the MICP technique in improving the undrained shear strength of soft clay soil using two native urease producing bacteria that help in the precipitation of calcite to increase the cementation between soil particles. Three concentrations of each of the locally prepared Bacillus sonorensis are used in this study for cementation reagent (0.25M, 0.5M, and 1M) during the period of treatment. The results showed that the native isolated bacteria have high activity in bindings the soil particles together. The results of unconfined compressive strength tests showed that using MICP helps increase the undrained shear strength of soil by (3-5 times) for C11 types of native isolates, but the D11 was (1.5-2 times) because two types have different activity. This study's main finding is using the native urease-producing bacteria isolated from Iraqi soil in the MICP technique for the biocementation of soil, which is considered one of the sustainable techniques in the construction industry.

Assessment of Some Geotechnical Properties for Soils of Euphrates River Banks (Kufa- Mishkhab), Middle of Iraq

Twelve stations in the cities of Kufa and Mishkhab were selected for studying the geotechnical, including physical, engineering, chemical and mineralogical, properties of soils in the river banks along the Euphrates River. Grain size distribution of the bank soils showed higher silt than clay and sand percentages. Soil samples from the 12 stations were classified according to the USCS standards. Silt with low plasticity constituted 91% of the silt fraction, whereas that with high plasticity composed 9%. The saturated density values ranged between 1.75-2.073 g/cm3 with an average of 1.953 g/cm3, while the dry density values ranged between 1.307-1.740 g/cm3 with an average of 1.553 g/cm3. The values of the dry and saturated density are within the permissible limits. Direct shear test showed cohesion values (C) that ranged between 15-55 kN/m2 with an average value of 34.8 kN/m2. The values of the internal friction angle (Ø°) of the clay type of soil with low plasticity ranged between 8.5°-17° with an average of 9.91°. The Ø° values of the other soil types ranged between 9°-17° with an average of 25°. Therefore, clay with high plasticity had higher Ø° values than the permissible limits. The results of unconfined compression test showed a range of 22.802-58.587 kN/m2 with an average of 38.173 kN/m2, with water percentage of 30%. The mineralogical tests of the bank soil performed using XRD analysis showed that the analyzed soil samples are composed mainly of quartz, calcite, chlorite, palygorskite, and montmorillonites. The pH value ranged between 6.4-7.55 with an average of 7.10, indicating low basicity. Gypsum concentrations ranged between 0.049-12.75 % with an average of 3.99 %, while that for carbonate ranged between 5-45 % with an average of 26.16%. Sulphates concentration ranged between 0.23-5.93 % with an average of 1.85%. Several treatment measures are proposed to stabilize the soil of the studied area.

A Study on Tensile Strength of Compacted Fine-Grained Soils

The tensile strength of clay is a major mechanical parameter and the main controlling parameter of tensile crack development which is generally encountered in geostructures. In this experimental study, 8-shaped direct tensile test and split tensile test were used to measure the tensile strength of compacted clay soil. Unconfined compression tests on the same clay samples were also carried out. Tensile strength and unconfined compression test results were compared. Laboratory tests were performed on Ankara clay and Kaolin clay with the addition of various proportions of synthetic polypropylene fiber, pulverized rubber, metal swarf, and bentonite. The data between the results of 8-shaped direct tensile tests, split tensile tests, and unconfined compression tests were correlated. This usage of different stabilizing agents enabled the authors to observe the reliability of the tensile strength measurement methods when soils’ mechanical properties were significantly changed and to develop universal equations which also can be applied to stabilized soils. The ratio of 8-shaped tensile strength to split tensile strength and to unconfined compressive strength was calculated to be 1.9 and 0.4, respectively. Also, the ratio of split tensile strength to unconfined compressive strength was calculated to be 0.2. Three equations were developed according to the Ankara clay and Kaolin clay mixtures’ tensile strengths, index properties, and compaction characteristics and proposed to estimate the tensile strength of fine-grained soils from their index properties.

The Effect of Acidic and Alkaline Chemical Solutions on the Behavior of Collapsible Soils

In this research, the effect of acidic and alkaline chemical solutions on the behavior of loessial soil was investigated. To evaluate the severity of acidity and alkalinity of chemicals, two factors sulfuric acid and sodium hydroxide were used in the pH of 3, 5, 9, 11. In this research, the effect of acidic and alkaline solutions on the collapse potential, shear strength parameters and unconfined compression of collapsible soils were investigated. Experimental tests results showed that acidic solutions with a low pH increase the collapse potential and effective cohesion of soil and decrease effective internal friction angle; on the other hand, alkaline solutions with a high pH decrease the collapse potential and effective cohesion of the soil and increase effective internal friction angle. The results of unconfined compression tests showed that with increasing the acidity and alkalinity in soil, the undrained strength of the soil decreased. SEM test results showed an increase in soil cavities in acidic solution while the soil cavities were fixed in alkaline solution.

Geotechnical properties of sandy clayey soil contaminated with lead and zinc

Previous studies have shown that pore fluid influences the geotechnical properties of soils. The aim of this paper is to investigate the effects of various concentrations of lead nitrate and zinc nitrate hexahydrate heavy metals in pore fluid on geotechnical properties of kaolinite–sand mixtures based on laboratory tests. Remolded samples of kaolinite–sand mixed with 5 and 25 cmol/kg-soil concentrations of $${\text{Pb}}\left( {{\text{NO}}_{3} } \right)_{2}$$ and $${\text{Zn}}\left( {{\text{NO}}_{3} } \right)_{2} \cdot 6{\text{H}}_{2} {\text{O}}$$ solutions were prepared. One-dimensional consolidation tests, direct shear tests, unconfined compression tests, consistency tests, sediment tests, adsorption tests, and X-ray diffraction tests were conducted on samples to investigate the changes in geotechnical properties of samples in the presence of heavy metals in pore fluid. The results indicate that the presence of Pb(II) and Zn(II) would decrease the initial void ratio and sedimentation of samples which is attributed to the noticeable changes in soil microstructure. With increasing Pb(II) concentration from 0 to 25 cmol/kg-soil, the void ratio of kaolinite containing 10, 25 and 40% sand decreased 18, 24 and 32% respectively. In addition, the reduction rates in similar samples containing Zn(II) were 14, 19 and 23%. The liquid limit of samples also decreased when the concentration of heavy metals increased to 25 cmol/kg-soil. The reduction in liquid limit was 21%, 15% and 14% for Pb(II) and 16, 12 and 7% in the presence of Z(II) for samples with 10, 25 and 40% of sand respectively. Significant decrease in the amount of cohesion also observed according to the test results. In the ratio of 40% sand the cohesion decreases 51% and 24% for Pb(II) and Zn(II) when the concentration of heavy metal increased from 0 to 25 cmol/kg-soil. The results of unconfined compression tests show that there is noticeable reduction up to 52% due to Pb(II) with the concentration of 25 cmol/kg-soil in the ration of 60% kaolinite and 40% sand.

ANALISIS BALIK KUAT GESER TANAH TERSTABILISASI SEMEN DENGAN METODE NUMERIK

Shear strenght is a parameter to soils strenght analysis. Shear strenght can be obtained from laboratorium test that interpreted as stress and strain. Soil tests had done on soil stabilization of cement with mixing 5%; 10%; 15% of content. Soil tests were used by triaxial test of unconsolidated undrained (triaxial UU) with cell pressure at 50; 100; 200 kN/m2 and unconfined compression test. The test specimens were disturbed soil samples which compacted and remolded, and then carry out curing for 0; 3; 7; 14; 28 days. The laboratory test results were back analysis in Plaxis 2D by using Mohr-Coulumb and Hardening Soil model later. The Mohr-Coulumb and Hardening Soil model had deviator stress results was almost equal to the test results of triaxial UU and unconfined compression test. Especially of strain by Mohr-Coulumb model, shew the lower strain than be showed by triaxial UU test and unconfined compression test. The Hardening Soil model, provides fluctuating strain results of triaxial UU test because it is affected by the application of cell pressure (σ3) and it provides greater strain results from unconfined compression test.
 
 Keywords: Triaxial UU, Unconfined Compresssion, Stress and Strain, Plaxis 2D

Undrained Shear and Pore Space Characteristics of Treated Loose Sands with Lime-Activated Zeolite in Saturated Settings

Abstract This research investigates the mechanical behavior of artificially cemented sandy soils formed by lime alkali activation of natural zeolite under saturation settings. In order to verify the bar capability of cemented sands with this new method, an analysis of the undrained shear strength of the soil with pore water pressure ratio measurements was performed from the interpretation of the results of unconfined compression tests. The effect of zeolite-lime blend on treated sands was also visualized by scanning electron microscopy. For the studied soils, it was concluded from the unconfined compression stress values that the soil is fully capable of withstanding compressions due to overburden pressure. Additionally, this study seeks to evaluate the effect of the void ratio on the pore space and undrained shear strength. The results showed that pore water B-ratio increases with the decrease of the void ratio. Moreover, with the increase of zeolite content, confining pressure, and curing age, the peak failure strength increases. The results indicated a promising consistency of treated samples with lime and zeolite under various values of undrained shearing and B-ratios, making this method an ideal treatment for loose sand deposits.

Soil-Compost Mixture as Alternative Material for Soil Cover Landfill

One of typical problem in a developing country is the lack of controlling odors, vectors, fires, and litter in the waste landfill. It is known that this problem can be reduced by landfill. However to maintain cover material always available, it is uneasy, especially due to limited budget. This study intends to propose compost-soil mixture as an alternative material using residual soil cover from completed waste landfill. In order to investigate and assess the geotechnical properties of soil-compost mixture as an alternative material, several tests were conducted such as compaction, unconfined compression, and permeability tests. Compaction tests showed 0.4%, 0.8% and 1.2% of compost in soil mixtures results the values of dry density in the range between 1.297 g/cm3 and 1.330 g/cm3, which meet the minimum requirement according to Indiana environmental department USA. Shear strength of compost-soil mixture that derived from results of unconfined compression tests, reduced slightly for additional compost without curing time. However, the values increased sharply for 3 and 7 days of curing time. All the shear strength values of 0.88 kg/cm3 to 34.76 kg/cm3 passed the minimum requirement for cover material according to Environmental Protection Agency (EPA) and Environment Agency. In case of ability of the soil mixture to transmit water, permeability coefficient were 1.5 × 10−3 cm/sec, 7 × 10−4 cm/sec and 3 × 10−4 cm/sec for 0.4%, 0.8% and 1.2% of compost respectively. Referring to modern sanitary landfill and design, it was shown that, the soil mixtures meet minimum requirement for permeability coefficient. To sum up, compost-soil mixtures with composition tested can be considered as material alternative for soil cover in landfill.

Effect of rubber tire on behaviour of subgrade expansive Iraqi soils

In this study focuses on improving an expansive soils geotechnical properties treated by tire crumble and decreasing the natural contamination by this waste material. The waste rubber of tire in the form of crumble with size ranging between 0.08 to 2 mm with proportion from 0 to 10% was used in this examination. Routine tests such as compaction, unconfined compressive strength, consolidation and swelling pressure test have been done on untreated and treated soils with crumble tire rubber. According to the test results it was found that, the maximum dry density of treated samples decrease with increased tire crumble content, while a slight reduction in the optimum moisture content was found simultaneously. Also, the results of unconfined compression tests showed that, the crumble tire rubber could not improve the properties despite the fact that that the soil still in the hardened consistency. In like manner results demonstrate that using crumble rubber might be successful procedure in upgrading the soil characteristics against swelling potential of soils by approximately 29.8, 43.4, 49.39, 14.77 times than untreated soil for (1, 3, 5, 10%) tire crumble rubber content. In addition the results show increasing crumble tire rubber content from 1 to 5% gave low displacement values by about (26.01 - 43.9)% than its value in untreated samples. Finally, it has additionally seen that using of crumble tire rubber aides in decreasing the compression index, consolidation coefficient, permeability coefficient and volume change coefficient.