Untrained shear strength is the main parameter in most problems concerned with short-term stability or total stress analysis states (TSA). Mechanism of soil deposit formation leads to inherent variability in soil strength and stiffness parameters.Inherent variability as the primary source of uncertainty in geotechnical problems consists of deterministic and stochastic components. In this paper, a generic deterministic trend is proposed by utilizing a good amount of well-documented in-situ test data. The new concept of transformation depth was introduced as the depth where it changes from a decreasing trend to an increasing one. Random field theory and local average subdivision (LAS) technique was employed in order to produce realization of untrained shear strength. Untrained shear strength was assumed to inherit a deterministic trend in vertical direction while preserving its stochastic behavior in horizontal direction.

Series of undrained monotonic triaxial tests and cone penetration tests were conducted on loose silty sand samples to study correlation between undrained shear strength of silty sands (Sus) and piezocone test results. CPT tests were conducted at 27 silty sand samples in calibration chamber. The results indicate that, in low percent of silt (0-30%), as the silt content increases, the undrained shear strength (Sus) and cone tip resistance (qc) decreases. It is shown that, fines content affects undrained shear strength (Sus) and cone tip resistance (qc) similarly. On the basis of obtained results, equations were proposed to determine the normalized cone tip resistance (qc1n) and undrained shear strength (Sus) of silty sand in term of fines content. Finally based on those equations, a correlation between normalized cone tip resistance and undrained shear strength of silty sand is presented. It is shown that the normalized undrained shear strength and normalized cone tip resistance of loose silty sands (F.C.<30%) decreases with increase of silt contents.

Expansive soils can be problematic in that they impose significant economic damages on the construction projects worldwide due to their high volume change in wet-dry conditions. Annually, many structures have been constructed on expansive soils such that nearly 60 percent of them undergo minor damage such as different kinds of fissure while 10 percent face severe unrehabilitatable damages. In this research, the cement and zeolite have been used as the base and supplementary cementitious stabilizers, respectively, and the undrained behavior of the treated expansive clay has been investigated. Hence, 6, 8, 10, and 12 percent of cement and 10, 30, 50, 70, and 90 percent of zeolite replacement were employed to cast the specimens. In the following, using the unconfined compression strength (UCS) and unconsolidated undrained triaxial (UU) tests, it can be stated that the best geotechnical performance such as maximum UCS, deviator stress in UU tests, secant modulus of elasticity (E50), cohesion, and internal fraction were obtained at 12% cement addition and 30% zeolite replacement after 28 days of curing. In both tests, increase in the cement content led to the increment in the failure strength of the samples. Based on the analysis of the results, it can be stated that the best geotechnical characteristics such as UCS, maximum deviational stress in triaxial test, secant modulus of elasticity (E50), and cohesion and internal friction angle were derived from the specimen stabilized with 12 percent of cement and 30 percent zeolite replacement cured in 28 days. With the above said, it can be noted that the optimum amount of zeolite replacement was 30%. Cement increment led to the enhancement of mechanical performance. Increase in zeolite replacement reduced the brittleness of the samples. In addition, increase in the curing time improved the mechanical behavior of the stabilized samples. The microscopic view justified the improvement of the stabilized samples.

The construction of geotechnical structures in sandy soils requires load bearing evaluation in undrained conditions. Undrained shear strength depends on many factors, including principal stress rotation (anisotropic behavior). However, the effect of this inclination angle (α°) is often ignored due to the difficulty in reflecting this phenomenon in laboratory research, the hollow cylinder torsional shear apparatus provides the possibility of examining the anisotropy of soils. On the other hand, most of the sand sediments contain different amounts of silt particles, which have a significant effect on the behavior of the sand, and investigating the anisotropic behavior of these mixed soils (especially in low content) has not been fully studied. This research includes 18 undrained tests using a hollow cylindrical apparatus on Firoozkuh sand with low silt content. The samples have 0, 5 and 10% silt content. Inclination angle (α°) is considered as a key parameter that shows the characteristics of anisotropy, and the values of 15, 30 and 60° are applied in the experiments. Based on the obtained results, increasing the inclination angle leads to more contractive behavior in sand. By adding a small percentage of layer, the overall structure of the sand skeleton remains constant and the samples can still be evaluated based on the general behavior of the host sand. In the samples containing 5%, reduction of contractive behavior and increase of resistance (18.5%, 12% and 7.7% for angles of 15, 30 and 60°, respectively) are observed, but with an increase of 10%, the strength is decreased (less than the host sand) and the contractive behavior is increased. In anisotropic behavior, with the increase of the inclination angle, the effect of fine grains in increasing the strength and reducing the contractive behavior of the samples as an important parameter in mixed soils is decreased.

In order to evaluate the shear strength parameters of compacted soils precisely it is necessary to determine these parameters in the laboratory by the compaction tests using remolded samples. The laboratory compaction test conditions should be comparable to the field compaction conditions. It is a common practice to conduct the compaction test in the laboratory using the dynamic compaction method (Proctor method) in which compaction is being performed by a hammer whereas sheep foot and smooth steel rollers are utilized in the field. In this study, evaluation of the effect of various compaction methods on shear strength parameters c and j and unconfined compression strength qu of soils has been done. The fine-grained soils selected in this study have been CL-ML, CL and CH classified according to Unified Soil Classification System. Static and dynamic compaction tests have been conducted on many remolded soil sample. The unconfined and triaxial compression tests have been done on these samples. The results of the unconfined and triaxial tests obtained from the samples compacted by the static method have shown greater strength compared to those obtained from the dynamic method.However, statistical studies indicate that the method of compaction has no significant effect on the shear strength of soils.

Statement of Problem: Evaluation of new adhesives efficacy in bonding orthodontic brackets to enamel has led to different results. The new measuring method, micro-shear bond strength, is preferred as an accurate method due to its ability to reduce confounding factors.Purpose: The purpose of this study was to evaluate and compare the micro-shear bond strength of three different adhesive systems for enamel surface preparation before bracket bonding.Materials and Method: In this experimental study, 90 extracted premolars were randomly divided into three groups of 30. Transbond XT was bonded to enamel after enamel surface preparation with acid etch in the first (control) group, Transbond plus self-etch primer in second group, and Adper prompt L-pop self-etch adhesive in third group. Then each group was randomly divided into two subgroups of 15. Micro-shear bond test was performed after 24 hours (T1) and 3-months (T2). Bond failure mode was also evaluated according to Adhesive Remnant Index (ARI). Two way ANOVA and Tukey tests were used for bond strength evaluation in groups, and mode of bond failure was analyzed with Kruskall Wallis and Mann Whitney tests.Results: The highest bond strength was found in acid etch group (29.17 MPa). Difference of bond strength at two intervals was statistically significant in all groups ( p <0.001). Bond strength difference between T1 and T2 was also significant in three groups ( p <0.001). However changes over time in three groups did not reveal any significant differences ( p = 0.091). Bond failure analysis demonstrated significant differences in ARI between groups.Conclusion: Bond strength of acid etch group was the highest and self etch primer showed higher bond strength than self etch adhesive group. Less adhesive remnant was found in self etch group.

The effects of cementation and the physical properties of grains on the shear behavior of grouted sands are investigated in this paper. The consolidated-undrained triaxial shear behavior of three grouted carbonate sands with different physical properties, including particle size distribution, particle shape and void ratio, was studied. Two sands were obtained from the north shores of the Persian Gulf, south of Iran, called Hormoz and Kish islands sands, and one sand was obtained from the south beaches of England and called Rock beach sand. The selected sands were grouted using a chemical grout of sodium silicate and tested after one month of curing. Test results showed that the effect of bonding on the shear behavior and strength depends on the bond strength and confining pressure. In addition, the shear behavior, yield strength and shear strength of grouted sands under constant conditions, including the initial relative density, bonds strength, confining pressure and loading, were affected by the physical properties of the sands. Furthermore, the parameters of the Mohr-Coulomb shear strength failure envelope, including the cohesion and internal friction angle of grouted sands under constant conditions, were affected by the physical properties and structure of the soils.

Most natural sandy deposits contain low amounts of fine content (clay and silt) that have complicated effects on the undrained behaviour of sands. In this research, the effect of low fine content (clay kaolin and Firuzkoh silt) on the undrained behaviour of sands with five percentages of fine grains (0, 3, 5, 7 and 10%) was investigated. For this purpose, 18 undrained compressive tests were carried out using strain control Torsional Shear Hollow Cylindrical Apparatus (HCA) on Firozkouh sand. The specimens were prepared in the laboratory by the Dry Funnel Deposition Method and consolidated under P'c= 100 and 200 kPa. By adding silt particles of up to 5%, the peak strength of the specimen increased (about 18.5%) and then by adding 5% of silt the peak strength decreased (about 13%) leading to an increase in the brittleness index and sensitivity to static liquefaction. With the addition of kaolin clay, a downward dominant trend in strength was observed (about 22% decrease in 10% clay) and the contractive behaviour increased. This result can be attributed to the nature of clay as the accumulation of clay particles on the contact surface of sand grains leads to the creation of an open microstructure with loose connections.

Background & Aim: More than 30 years has passed since introduction of glass-ionomer cement as a dental restorative material, luting cement and liner. Although they are sensitive to moisture and desiccation during the initial setting stages, relative poor physical properties because of chemical bonding to tooth substrate, and long-term esthetic quality, they are recommended for restoring anterior and posterior primary teeth, cervical lesions and root caries of permanent teeth. In this study, shear bond strength of Fuji II was compared with of ariadent glass-ionomer cements. Materials & Methods: Thirty intact extracted primary molars were prepared for this study. Selected teeth were divided in two groups of 5. Sample were free of caries, fracture, crack, discoloration or any structural abnormality. The dentin of buccal surface of teeth were exposed by microtome apparatus. The surface was conditioned by polyacrylic acid (10%) for 20 seconds. Glass ionomer cements (Fuji II, and Ariadent) were prepared in a plastic cylinders (15 of each) and attached to the dentin of teeth horizontally. Shear bond stength of materials was measured by instron (Model 1159).Results: Mean shear bond strength of Ariadent cement was 4.2±1.9 Mpa while 7.4±1.5 Mpa was of Fuji II cement (P=0.000).Failure mode was similar between two cements (P=ns). The most prevalent type of failure mode was cohesive failure leaving a firmly attached thin and homogenous layer of cement to dentin, in both groups.Conclusion: It appears that shear bond strenght of Ariadent cement to primary tooth is much lower than of Fuji II.

Sistan River is one of the main rivers in Sistan plain which has the various hydraulic structure built upon it. Parts of the river and its structures have been influenced by the entrance of sediments into the river’ s bed which are due to several reasons such as drought, extreme wind, and transportation of fine sediments. The research regions included the water entrance to Chahnime, Kohak dam, Zahak Dam, Sistan Dam, and Nohrab Bridge. In the first stage, the direction of the river in respect to dominant wind and the condition of shores facing wind are studied, and the natural and artificial obstacles, such as vegetation, natural heights, and buildings, which were in the path of the wind, were determined. In the second stage, soil texture, dry unit weight and soil coherence of shores facing wind were measured. Based on the research, the Sistan River direction was parallel, oblique, and perpendicular in respect to the dominant wind direction. The soil texture was mainly silty clay with gravel, loam, and loamy sand. However, the soil texture changed at the riversides to loam and silty loam. The liquid limit of the studied soils was lower than 25 with little soil coherence. The undrained shear strength of surface soils within the path of the river and its shores were determined less than 30 kPa. Also, the range of dry unit weight of soil in the studied area is between 1. 2gr/cmᶾ to 1. 3gr/cmᶾ and its vegetation indicated vegetation was lower than 20% near the engineering structures. The results of this study indicate that the, Kohak dam, the Sistan dam, and Nohrab bridge, have the most impact on erosion and transport of wind sediments.