Silty Sand Soil Research Articles

Integrated Ground Penetrating Radar and Electrical Resistivity Study to Explore Such Basrah Low Resistivity Soils for Engineering Purposes, Southern Iraq

A total of 45 ground penetrating radar profiles have been conducted in Basrah City, Southern Iraq, to detect buried utilities in such soils which have not been tested before. This study tries to explore how much this technique can be useful for Basrah low resistivity soils during arid and humid seasons. In Basrah University Campus (silty clay soil) and Basrah Sport City (silty sand soil), 37 and 8 ground penetrating radar profiles were achieved inside these locations respectively. Vertical electrical sounding (Schlumberger array) and electrical profiling (Wenner array) were also used in compatibility with radar surveys side by side in all sites. Here, radargrams do not reveal much more details about the subsurface conditions because of the moisture content and soil characterizations. The actual penetrating depth of 250 and 500 MHz antennas are limited to 1.4 and 0.4 m respectively due to the soil total dissolved solids of about 6790 ppm. The tests suggest that the 250 MHz antenna is somewhat better than the 500 MHz one for detecting the shapes and depths of the buried bodies in silty clay soils during rainy or even arid periods. In Basrah Sport City (500 MHz) antenna, the radargram wave signals are not good for more than 2.5 m depth, and this antenna, rather than the 250 MHZ one is suitable for silty sand soil type.

Geotechnical characterization of soils in the northern zone of Brazzaville

The geotechnical classification of soils by laboratory tests is usually used to determine the class of the soil under study for its subsequent use in construction projects. The interest is certainly well displayed. Indeed, an experimental program has been developed with the aim of studying the soil in the study area. To this end, oedometric and shear tests were carried out on several soil samples in the laboratory. This made it possible to understand the “stress-strain” behavior of these soils. As a result, the presence of a silty sand soil was found that is susceptible to collapse.

BEHAVIOUR OF SILTY SAND REINFORCED WITH LOW DENSITY POLYETHYLENE (LDPE) STRIPS

In this study, silty sand is reinforced with plastic strips to improve the engineering properties of soil. Sand and silty sand soils have been used as base materials and low-density polyethylene (LDPE) strips as reinforcement materials. The LDPE strips are used in various dimensions (e.g., width ranging from 6 to 15mm and length ranging from 15 to 30mm). The randomly distributed LDPE strips are added to sand and silty sand specimens at varying percentages (e.g., 0.1% to 0.3%) by weight of dry soil specimen. Direct shear tests are performed on sand and silty sand specimens in both unreinforced and reinforced conditions. Stress strain, volumetric strain (e.g., compression/dilation behaviour) and strength envelopes are plotted to investigate the improvement in the shear strength parameter (e.g., internal friction angle). The results show that in sand specimens, the maximum improvement in shearing behaviour has been achieved with strips of 6x30mm in dimensions and at 0.3%. For silty sand specimens, the maximum improvement in shearing behaviour has been achieved with strips of 6x25mm in dimensions and at 0.3%. In addition, it has been observed that reinforced soil specimens increased the values of internal frictional angle compared to unreinforced soil specimens. In sand specimens, maximum increase of 19.72% in internal friction angle (Φ) has been observed with 6x30mm strips at similar percentage. In case of silty sand specimens, the maximum increase in internal friction angle (Φ) has been observed as 19.28% with the addition of strips of 6x25mm and at 0.3%.

Effect of Se-Enriched Irrigation Water on the Biomass Production and Elemental Composition of Green Bean, Cabbage, Potato and Tomato.

Additional Selenium (Se) intake may be recommended in areas of Se deficiency to prevent various human diseases. One possibility for this is biofortification. In this experiment, the effect of irrigation water containing 100 and 500 µg L−1 Se, in the form of Na2SeO4, on green bean, cabbage, potato and tomato was investigated in a greenhouse pot experiment with sand, silty sand and silt soils. The chlorophyll content index was usually improved by Se and was significantly higher in potato in sand and silty sand and in tomato in silty sand and silt soils. The Se content of edible plant parts increased 63-fold in the 100 µg L−1 Se treatment and almost 400-fold in the 500 µg L−1 Se treatment, averaged over the four species and the three soils. Irrigation water with a Se content of 100 µg L−1 may be suitable for the production of functional food in the case of green beans, potatoes and tomatoes. However, due to its greater Se accumulation, cabbage should only be irrigated with a lower Se concentration. The use of Se-enriched irrigation water might be a suitable method for Se biofortification without a significant reduction in plant biomass production and without a remarkable modification of other macro- and microelement contents.

Assessment of the reuse of Covid-19 healthy personal protective materials in enhancing geotechnical properties of Najran's soil for road construction: Numerical and experimental study

The COVID-19 pandemic has not only caused a global health crisis, but it has also had significant environmental and human consequences. During the COVID-19 pandemic, this study focused on emerging challenges in managing healthy personal protective materials (HPPM) in Kingdom of Saudi Arabia, using silty sand (SM) soil as an example since it covers large areas in KSA and in the whole world. The main objective of this paper is to find a novel way to minimize pandemic-related waste by using HPPM as waste materials in road construction. For the first time, a series of experiments was conducted on a mixture of different percentages of shredded HPPM (0, 0.5, 1 and 2%) added to the silty sand (SM) soil for road applications, including soil classification according to the USCS, modified compaction, UCS, UPV, and CBR. In addition, a numerical simulation was performed using geotechnical-based software Plaxis 3D to study the performance of the soil-HPPM mix as a subbase layer in the paving structure under heavy traffic loading. The modified compaction test results show that there is an increase in the optimum moisture content with increasing the HPPM contents from 0.5% to 1% and 2%. However, a reduction in the maximum dry density is observed. The values of dry density and water content at 0%, 0.5%, 1% and 2% pf HPPM are 2.045, 1.98, 1.86 and 1.8 g/cm3 and 7.65% 8%, 8.5% and 9.5%, respectively. The soaked CBR values at 0, 0.5, 1 and 2% HPPM are 23, 30, 8, 2% with the maximum value attained with the addition of 0.5% HPPM. The results of UCS were with the same percentages of HPPM 430, 450, 430 and 415 kPa, respectively, with the maximum value attained with 0.5% HPPM addition as well. In contrast, the values of UVP at 0%, 0.5%, 1% and 2% are 978.5, 680.3, 489.4 and 323.6 m/s, respectively, confirming the trends obtained by modified compaction test results. The simulation results confirm this conclusion that the soil-HPPM mix show a superior performance when used as a subbase layer and reduced vertical displacement by a percentage of 11% compared to the normal subbase material. By eliminating HPPM especially facemasks from the landfill lifecycle, incorporating them into high quality construction material production has the potential to deliver significant environmental benefits.

Evaluation Of Use of Stone Column in Unengineered Closed Landfill Soil

In the building industry, ground improvement techniques based on stone column are widely employed. It is a very successful approach for enhancing the engineering characteristics of soil in all aspects, as well as reducing the settling issue in poor-grounded soils including silt, clay, silty sand, and organic soil. The performance of stone columns, is determined by the confining pressure provided by the surrounding soils. Engineering constructions built on thick layers of soft soil strata face issues such as limited bearing capacity, excessive total and differential settlement, lateral spreading, and so on. To address such issues, many ground improvement techniques are available. In exceptionally soft soils, the lateral confining pressure may be inadequate, resulting in column bulging failure. Individual stone column encasement improves lateral resistance to bulging by adding restricting pressure. This research focuses on the geotechnical aspects of building on closed landfill sites. A total of 33 models were tested in a geotechnical engineering laboratory on virgin former landfill soil and stone column with and without encasement in this current study. The increased diameter, length and L/D ratio of the column has demonstrated that the load capacity has increased and soil settling has decreased. When an unreinforced stone column has been installed, the ultimate bearing capacity of landfill soil is increased by 75-112.50 per cent and 87.50-176 per cent respectively, for 10mm and 20mm diameter stone column. Furthermore, when a fully reinforced stone column has been installed, it had increased by 156.25-212.50 per cent and 200-298 per cent for 10mm and 20mm diameters respectively. The stiffness of soil is increased by the stone column, which contributes to increase in the load capacity. The geogrid layer confines an aggregate, which contribute to enhance shear stiffness and bearing capacity.

Vertical Displacement of a Single Pile Due to Axial & Lateral Loads

Pile foundation supports the upper structure to the subgrade, generally vertical loads. Still, if horizontal loads are very dominant, such as bridges, tall buildings, and tower structures, it must be calculated. Pile foundations with combined loads are generally analyzed. The axial load is first to determine the axial carrying capacity and vertical displacement, then the lateral load to determine the lateral bearing capacity and lateral deflection. In the field, the two loads work together/simulant. In Indonesia, loading tests do not simultaneously, so in construction, it does not account for the additional vertical displacement and lateral deflection due to the load that works simulant. However, there has been an association in ASTM D3966-07 about the simulant loading test. This research will investigate the analysis and experimental laboratory, the effect of vertical displacement on a single pile foundation, as the effect of combined loads. Also, it gets a relationship that can be used as a reference for analyzing additional vertical displacement due to combined loads on pile foundations based on available independent loading test. The research will be divided into two stages. Stage I is an analysis with the Finite Element Method (FEM) approach. Phase II is a laboratory model experimental test, which is inbox (100x100x80) cm3 filled silty sand soil as an illustration of conditions in the field, single pile foundation using steel with a length of 50cm and 60cm, the diameter of 1.5cm and 2cm, with axial and lateral load variations and combined loads. The results obtained show that after adding vertical load (Pu) about 5x, lateral load (Hu) on (Pu/Hu > 5) and the vertical displacement stays like the loading test until it collapses. Another (Pu/Hu ≤ 5), the lateral load, will increase the significant vertical movement due to the combination load. With axial load five times greater than lateral load, there is no increase in vertical displacement. Still, at an axial load less than five times the lateral load, there is an increase in vertical displacement that needs to be considered.

Effect of Bacillus polymyxa as Wild or Mutant by UV and Diagnosed with PCR on the Available Phosphate Fertilizer in Calcareous Soils and Growth Yield of Corn (Zea mays L.)

An agricultural experiment was conducted to study the effect of corn seeds inoculation with mutant, wild or mixed of them together of locally isolate of Bacillus polymyxa on the availability of phosphorus, growth and yield of corn (Zea mays L.) when it was planted in silty clay and loamy sand soils with the addition of four levels of triplsuperphosphate fertilizer (0, 50, 75 and 100 kg p/ha). B. polymyxa isolate was exposed to UV rays for 60 minutes to obtain mutagenic bacteria. Results showed that inoculation with wild isolate with 75 or 100 kg p/ha gave the best value for plant height, shoot dry weight, phosphorus concentration in the vegetative part and available phosphorus in the soil after planting. Inoculation with mutagenic isolate bacteria gave the value of 69.37 cm, 6 g/pot, 43.49 mg/pot and 27.52 mg/kg soil for plant height, shoot dry weight, phosphorus absorbed in vegetative part and available phosphorus, respectively when it planted in loamy sand or silty clay soil. On the other hand, the percentage of increase of the effect of phosphate fertilization levels was 47.82%, 39.70%, 75.53% and 73.46% in loamy sand soil and 46.74%, 56.96%, 85.33% and 53.12% in silty clay soil, respectively.

Effect of the Boron Concentration in Irrigation Water on the Elemental Composition of Edible Parts of Tomato, Green Bean, Potato, and Cabbage Grown on Soils With Different Textures.

The most important environmental source of boron (B) contamination is irrigation water. The data on the effect of B on the elemental composition in the edible parts of vegetables are scarce. A greenhouse pot experiment investigated the effect of irrigation water containing 0.1 and 0.5 mg/L B on the biomass, elemental (e.g., B, Mg, K, Fe, Cu, and Zn) composition, and photosynthetic parameters of tomato (Solanum lycopersicum), green bean (Phaseolus vulgaris), potato (Solanum tuberosum), and cabbage (Brassica oleracea) plants grown on 10 kg of sand, silty sand, or silty soil. The biomass of the edible part was unaffected by B treatment. The soil type determined the effect of B irrigation on the elemental composition of vegetables. The B content increased by 19% in tomatoes grown on silty soil. The 0.1 mg/L B treatment facilitated tomato fruit ripening on all soils, and the 0.5 mg/L B treatment doubled its chlorophyll content index (CCI) on silty soil. The 0.5 mg/L B treatment negatively affected the nutritional value of green beans on all soils, decreasing the Fe and K contents by an average of 83 and 34%, respectively. The elemental composition of potato was unaffected by the treatments, but the CCI of potato leaves increased in the 0.5 mg/L B treatment by 26%. The B content was increased by 39% in cabbages grown on light-textured soils. In conclusion, B concentration of up to 0.5 mg/L in irrigation water had no significant beneficial or adverse effect on the investigated vegetables, but 0.1 mg/L B treatment could shorten tomato fruit maturation time on B-poor soils. The B levels in vegetables remained suitable for human consumption.

Improvement of Gravelly Silty Sand Reinforced with Biaxial Bamboo Geogrid

In this paper, performance of gravelly silty sand soil reinforced with geogrid are present and analyzed to improve the carrying capacity. For this, the geogrid was elaborated with a renewable material like bamboo with the same dimensions of polymer geogrids biaxial. This type of soil can be used for the construction of the sub-base and base of a pavement. California Bearing Ratio (CBR) tests was carried out to obtain the bearing capacity of the silty sand soil with and without bamboo geogrid. In addition, laboratory tests were carried out to obtain the mechanical properties of the bamboo. When comparing CBR results, an improvement in the bearing capacity was evidenced with the use of bamboo geogrid with a 20% increase in the carrying capacity. Finally, maximum tensile and bending strength of bamboo were 2000 kgf/cm2 and approximately 0.018 kgf/cm, respectively.

Stabilization Characteristics of Different Loose Sandy Soils using Microbial-Induced Calcite Precipitation

Loose sands (siliceous, silty, and calcareous classes) are extensively found near arid areas in Egypt. Furthermore, many geotechnical structures, like water channels and roads, may be constructed on weak or loose sand soils. The geotechnical behavior of loose sands is usually connected with different interdependent problems, such as high permeability, low shear strength, low bearing capacity, high seepage, and low stability. This work characterized the effect of stabilization of the siliceous, silty, and calcareous sandy soils via biocementation process using Sporosarcina pasteurii bacteria as a potential eco, commercial, and engineering solution. This was carried out using bacteria, fixation, and cementation solutions (BFC) at different times number additions. The results indicated that the addition times of solution have a remarkable effect on the physical and mechanical properties of sandy soils. The results also proved that the precipitation of calcite by the bacterial activity led to cohesion of soil grains, and this increased the resistance of soils to deterioration. In addition, the high content of the precipitated calcium carbonate enhanced the shear strength and the unconfined compressive strength and decreased the soil permeability. S. pasteurii bacteria can be used successfully and commercially in the biocementation process for siliceous sand, silty sand, and calcareous sandy soils in Egypt using the recommended conditions and mixes.

Experimental study on unconfined compressive and cyclic triaxial test behavior of agar biopolymer–treated silty sand

The need for space for infrastructure development has plummeted studies in ground improvement to an eminent research topic. But in the present day where the need for sustainability is of utmost importance, efficient and environment-friendly improvement methods have been coming up among which the use of biopolymers as a soil additive have gained popularity. In the current research, various strength aspects of agar biopolymer–treated silty sand soil have been explored. The unconfined compressive strength property of treated silty sand at varying agar dosages (0.5%, 1%, and 2%) at different curing periods (3 days, 7 days, and 28 days) was analyzed using laboratory investigations. Furthermore, the effect of frequency of loading on dynamic properties and pore pressure response of the agar-treated silty sand was also investigated by performing a set of strain-controlled cyclic triaxial test at different frequencies (0.2 Hz, 1 Hz, 1.5 Hz, and 2 Hz). The tests were performed at constant axial strain amplitude of 1% and at confining pressure of 100 kPa. The results demonstrated that with the increase in agar content and curing time, the unconfined compressive strength of soil also increased. Besides, a decrease in pore pressure build-up, decrease in secant shear modulus, and an increase in damping was observed on increasing the frequency of cyclic loading.

Effect of Liquid Polyvinyl Acetate and Micronized Calcium Carbonate on Strength Parameters of Silty Sand Soil

Effect of Liquid Polyvinyl Acetate and Micronized Calcium Carbonate on Strength Parameters of Silty Sand Soil

Mitigation of Dust Emissions of Silty Sand Induced by Wind Erosion Using Natural Soybean Biomaterial

Fugitive dust induced by wind erosion has been a serious environmental problem in many countries. In this research, a plant-derived urease enzyme named soybean, as a cheap and easily available enzyme-induced carbonate precipitation (EICP), is employed to stabilize loose soil-inducing fugitive dust. The tested silty sand soil was retrieved from one of the dust centers of Khuzestan-Iran with a low plasticity index. The treated experiments were prepared by two different methods of mixing and pouring the extract solution with and on the soil with both maximum and minimum densities. After a certain period of time, at which the calcium carbonate precipitation process was completed, unconfined compressive strength tests were conducted to monitor increase in the soil shear strength, treated with EICP. Then, water erosion test was conducted to evaluate resistance of the treated soil against water penetration and soil erosion due to water runoff. Later, trays containing bare and treated soils, obtained from different EICP applications, were sited in a wind tunnel to test their erosion performances. The results indicated that soybean enzyme which is much easier to prepare than the jack bean enzyme, previously suggested by other researchers, can control dust emissions induced by wind erosion.

Geotechnical characterization of plastic waste materials in pavement subgrade applications

Scarcity of traditional construction materials has motivated researchers to explore alternatives, and besides crushed glass, reclaimed asphalt pavement, and scrap tires, to name a few, plastic waste (unwanted or unusable plastic objects) has also gained attention in recent years. Plastic waste is traditionally re-used or recycled, but it often ends up as trash on curbsides, in landfills, or in our seas and oceans. The substantial amount of plastic waste produced annually worldwide, and its environmental repercussions are the rationale for exploring alternatives in order to recycle plastic waste into construction materials. This exploration can also benefit many industries and would help minimising adverse environmental impacts associated with dumping tones of plastic waste in landfills. Using plastic waste material with soil for soil reinforcement purposes has revealed some improvements in terms of strengths of materials, but nevertheless, this potentiality has not been fully assessed for different types and forms of plastic waste with natural subgrade soil in the road industry. In this paper, ground, flaky, and pelleted shapes of four sorted types of plastic waste from a recycling market were combined with silty or clayey gravel and sand soil of the A-2-7 AASHTO type. These plastic types are: low density polyethylene (LDPE), high density polyethylene (HDPE), polyethylene terephthalate (PETE), and polypropylene (PP) resins. Their various geotechnical properties have been assessed thoroughly. The investigation process entails assessing compaction, Californian Bearing Ratio (CBR), strength, resilient modulus, and permeability properties for both natural sub-grade soil and modified sub-grade soil with the aforementioned types of plastic waste. The results obtained show that the addition of plastic wastes decrease the maximum dry densities of the subgrade soils because of the lower relative density of the plastic material compared to the soil particles. It is also found that the addition of plastic wastes can increase or decrease the CBR and MR values of the subgrade. The nature of change (increase or decrease) and its magnitude are a function of the plastic content, shape and type. Permeability values of many subgrade soil samples increased with the addition of plastic waste, whereas the hydraulic conductivity of some soils modified with plastic remained unchanged. Subgrade soils with plastic had higher friction angle and lower compressive strength than plastic-free soils. The results of this research suggest that partial replacement of subgrade soil material with plastic waste may prove useful in road subgrade applications.

Evaluation of Dynamic Probing Testing Effect in Hand Excavated Pit on Test Results Using Numerical Modeling

In Iran, using the hand excavated pits (wells) have been more common compared to other countries. As a matter of fact, recent years, utilizing the dynamic probing test (DPT) in these types of pits has been significantly developed in Iran. This is while the standard state of doing this test is from the ground level. In this work, the dynamic probing test is carried out in two similar wells with diameter of 1 m and the depth of 10 m in two areas in city of Qom in Iran; one has silty sand soil and the other is clay. Then, both tests are simulated using numerical modeling in Abaqus software and the results are compared and calibrated with the values obtained at the mentioned sites. The results show a good agreement between the simulation data and tests done in the sites. After calibrating the simulated values with the values obtained from the site, we perform another simulation, this time, for the standard state (It means that the test is done from the ground level or with the assumption without well), as deep as 10 m and for both areas and with the mentioned soils specifications. The results show 35 and 22 percent difference in the dynamic resistance of cone’s tip between the testing in standard state and hand excavated pit, for silty sand and clay soils, respectively. Finally, using the simulation, we present the relations between the depth of the test point and dynamic resistance of cone’s tip for both states and both types of the soils studied in this paper.

Experimental and Numerical Analysis for Earth-Fill Dam Seepage

Earth-fill dams are the most common types of dam and the most economical choice. However, they are more vulnerable to internal erosion and piping due to seepage problems that are the main causes of dam failure. In this study, the seepage through earth-fill dams was investigated using physical, mathematical, and numerical models. Results from the three methods revealed that both mathematical calculations using L. Casagrande solutions and the SEEP/W numerical model have a plotted seepage line compatible with the observed seepage line in the physical model. However, when the seepage flow intersected the downstream slope and when piping took place, the use of SEEP/W to calculate the flow rate became useless as it was unable to calculate the volume of water flow in pipes. This was revealed by the big difference in results between physical and numerical models in the first physical model, while the results were compatible in the second physical model when the seepage line stayed within the body of the dam and low compacted soil was adopted. Seepage analysis for seven different configurations of an earth-fill dam was conducted using the SEEP/W model at normal and maximum water levels to find the most appropriate configuration among them. The seven dam configurations consisted of four homogenous dams and three zoned dams. Seepage analysis revealed that if sufficient quantity of silty sand soil is available around the proposed dam location, a homogenous earth-fill dam with a medium drain length of 0.5 m thickness is the best design configuration. Otherwise, a zoned earth-fill dam with a central core and 1:0.5 Horizontal to Vertical ratio (H:V) is preferred.

Small shaking table testing and numerical analysis of free-field site response and soil-structure oscillation under seismic loading

In this study, the accuracy level of geometric scaling factor (herein, λ = 45) selected for the shaking table test model represents the actual site conditions as discussed by comparing the results of both experimental data and numerical analysis obtained from the soil-structure oscillation and free-field response under seismic loads. The difficulty to be overcome in this experimental campaign was to investigate the limited soil size considered for this complex geodynamic problem due to the small capacity of the shaking table having payload of 2.5 kN and the geometry of testing platform of 1 m × 1 m, respectively. The superstructure used in the analysis of the soil-structure interaction is specified as six story building structure with height of 30 m resting on a silty sand soil with a shear wave velocity of 536 m/s. Within the frame of this work, the underlying soil is handled as a homogeneous single layer on the top of rigid bedrock. The diameter of the ground specimen and the bedrock depth were considered to be 26.23 m and 10 m, respectively. Special cylindrical flexible testing equipment was designed to hold the excavated soil volume in the container without deforming the experimental setup. In order to examine the seismic responses at the control points of the scaled test models under the nonlinear supporting effects, 2-D finite element analyses of the soil-structure system have been executed by using the PLAXIS simulation program. It is obviously seen that the soil layer parameters have significantly increased the free-field site response compared with the bedrock response under different seismic excitations. Based on the comparison of calculated results with experimental recordings, it is suitable to mention that small capacity shaking table experiments with appropriate scaled test models provides an alternative means of laboratory investigations even for such complex soil-structure coupling problems.

Low-level soluble chloride extraction in soil

Three methods of extraction of low-level soluble chloride contents from vadose-zone soil were evaluated in this study. Three methods were employed on a silty sand soil using a 2:1 fluid:soil ratio: 1) Method A utilized three successive rinses with deionized water; 2) Method B applied three successive rinses of 0.0001 M and 0.001 M Na2SO4 solution; and 3) Method C passed deionized water through the soil with a pressurized filtration system three times. Method A had lower standard deviation and yielded more consistent soluble chloride contents per rinse than method C; Method B was ruled out because of concerns that the Na2SO4 reagent contained trace amounts of chloride. Method A was applied with a 1:1 fluid:soil ratio in duplicate to 50 samples from a 34-m thick vadose-zone borehole, yielding a mean difference in duplicates of 13.9% and percent total extracted soluble chloride of 62.4 ± 9.9%, 25.2 ± 7.4%, and 12.4 ± 6.6% in each of the three successive rinses.•Three successive rinses of soil with deionized water achieved consistent extraction results.•Multiple rinses are necessary to extract soluble chloride if chloride contents are low.•This method is amenable to analysis of soil in vadose-zone borehole samples.

Analysis of the suction evolution during direct shear test in a silty sand soil

Shear strength of soils is one of the essential parameters for analysing and solving divers geotechnical problems (e.g. the bearing capacity of shallow footings pile foundations, slope stability and earth embankments). In this study, a series of conventional large-scale (300 X 300 mm) direct shear tests were carried out on saturated and constant water content silty sand specimens at ei = 0.6 and 1.0 tested under applied vertical stresses of 100, 200, or 400 kPa to investigate the influence of matric suction on the shear strength characteristics of the tested material. A loading steel cap was modified to allow the direct measurements of the matric suction using two commercial available Equitensiometer suction probes (EQ3). The experimental program indicated that, for both studied void ratios, the obtained shear strength of specimens under constant water content is found to be distinctly greater than those obtained from saturated samples. The results showed that the samples compacted at ei = 1.0 exhibited collapse behaviour during saturation stage, whereas same samples did not show any volume change during stabilisation stage when tested under constant water content condition. The study results also showed that the matric suction reduction during consolidation stage depends on initial void ratio of the tested samples as well as the level of applied vertical stress. Moreover, the matric suction evolution during shearing process of both studied void ratios specimens decreased with increasing the level of applied vertical stress.