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Showing 11 results for Shear Strength

S.a. Naeini, R. Ziaie-Moayed,
Volume 5, Issue 2 (6-2007)

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.
M.a. Khan, A. Usmani, S.s. Shah, H. Abbas,
Volume 6, Issue 2 (6-2008)

In the present investigation, the cyclic load deformation behaviour of soil-fly ash layered system is

studied using different intensities of failure load (I = 25%, 50% and 75%) with varying number of cycles (N =

10, 50 and 100). An attempt has been made to establish the use of fly ash as a fill material for embankments of

Highways and Railways and to examine the effect of cyclic loading on the layered samples of soil and fly ash.

The number of cycles, confining pressures and the intensity of loads at which loading unloading has been

performed were varied. The resilient modulus, permanent strain and cyclic strength factor are evaluated from

the test results and compared to show their variation with varying stress levels. The nature of stress-strain

relationship is initially linear for low stress levels and then turns non-linear for high stress levels. The test

results reveal two types of failure mechanisms that demonstrate the dependency of consolidated undrained

shear strength tests of soil-fly ash matrix on the interface characteristics of the layered soils under cyclic

loading conditions. Data trends indicate greater stability of layered samples of soil-fly ash matrix in terms of

failure load (i) at higher number of loading-unloading cycles, performed at lower intensity of deviatoric stress,

and (ii) at lower number of cycles but at higher intensity of deviatoric stress.

A. Arabzadeh, A.r. Rahaie, A. Aghayari,
Volume 7, Issue 3 (9-2009)

In this paper a new method based on Strut-and-Tie Model (STM) is proposed to determine the shear capacity of simply supported RC deep beams and an efficiency factor for concrete with considering the effect of web reinforcements. It is assumed that, the total carried shear force by RC deep beam provided by two independent resistance, namely diagonal concrete strut due to strut-and-tie mechanism and the equivalent resisting force resulted by web reinforcements, web reinforcing reduces the concrete compression softening effect with preventing from the diagonal cracks opening or concrete splitting. The unknown function and parameters are determined from 324 experimental results obtained by other researchers. To validate the proposed method, the obtained results are compared with some of the existing methods and codes such as ACI 318-05 and CSA. The results indicate that the proposed method is capable to predict the shear strength of variety of deep beams with acceptable accuracy.
Khelifa Harichane, Mohamed Ghrici, Said Kenai,
Volume 9, Issue 2 (6-2011)

When geotechnical engineers are faced with cohesive clayey soils, the engineering properties of those soils may need to be

improved to make them suitable for construction. The aim of this paper is to study the effect of using lime, natural pozzolana or

a combination of both on the geotechnical characteristics of two cohesive soils. Lime or natural pozzolana were added to these

soils at ranges of 0-8% and 0-20%, respectively. In addition, combinations of lime-natural pozzolana were added at the same

ranges. Test specimens were subjected to compaction tests and shear tests. Specimens were cured for 1, 7, 28 and 90 days after

which they were tested for shear strength tests. Based on the experimental results, it was concluded that the combination limenatural

pozzolana showed an appreciable improvement of the cohesion and internal friction angle with curing period and

particularly at later ages for both soils.

Abolfazl Arabzadeh, Reza Aghayari, Ali Reza Rahai,
Volume 9, Issue 3 (9-2011)

An experimental-analytical investigation was conducted to study the behavior of high-strength RC deep beams a total of sixteen

reinforced concrete deep beams with compressive strength in range of 59 MPaOf'c O65 MPa were tested under two-point top

loading. The shear span-to-effective depth ratio a/d was 1.10 all the specimens were simply supported and reinforced by

vertical, horizontal and orthogonal steel bars in various arrangements. The test specimens were composed of five series based

on their arrangement of shear reinforcing. The general behavior of tested beams was investigated. Observations were made on

mid-span and loading point deflections, cracks form, failure modes and shear strengths. The test results indicated that both

vertical and horizontal web reinforcement are efficient in shear capacity of deep beams, also the orthogonal shear reinforcement

was the most efficient when placed perpendicular to major axis of diagonal crack. Concentrating of shear reinforcement within

middle region of shear span can improve the ultimate shear strength of deep beam. The test results were then compared with the

predicted ultimate strengths using the ACI 318-08 provisions ACI code tended to either unsafe or scattered results. The

performed investigations deduced that the ACI code provisions need to be revised.

M. Gharouni Nik, M. Fathali,
Volume 11, Issue 1 (5-2013)

Geometrical profile (roughness) of joint surfaces influences the behaviour of rock joints under shear loading. With regard to the

dilation, there are two models of direct shear test that may simulate the original loading condition existing in the location from

where the specimens have been sampled. The first model in which the normal load is constant (CNL) and the discontinuity is free

to dilate in shearing, represents typical situations such as movement of a block on a surface slope as a result of its own weight.

The second model in which the dilatancy is prohibited (VNL), simulates the condition of a block confined in a rock mass in an

underground opening. A shear test conducted under restricted normal displacement (dilation) will generally yield considerably

higher shear strength than one conducted under constant normal stress. In this research, both types of tests were conducted on

smooth and rough surfaces of specimens made from rock like material. The results of the VNL and the CNL direct shear tests on

regular teeth-shaped profile discontinuities indicates that at all levels of normal load, the linear Mohr-Coulomb criterion was not

valid for rough surfaces that subscribed to the power law equations. Increasing normal load emphasized the difference between

the results obtained from two methods, although for lower normal loads the results were nearly similar.

Nader Shariatmadari, Amir Hossein Sadeghpour, Farshid Razaghian,
Volume 12, Issue 3 (7-2014)

This research shows the results of studies carried out to define and analyze the effect of aging on MSW behavior of Kahrizak Landfill, the biggest landfill in Iran. Studied samples consisted of fresh samples and also aged ones with 5.5, 14 and 21 years of age which were obtained by mechanical excavators in aged burial locations. Analyzing variation in MSW components illustrates that paste fraction of MSW decreases due to aging process while fibers show a rising trend. Also the moisture content and the organic content of MSW reduce below half of the initial values while the degree of decomposition (DOD) increase up to almost 60% after 14 years. These variations over the time are significantly related to the burying methods and environmental condition of burying location. Shear strength behavior of MSW material was analyzed by some CU tests using large scale triaxial apparatus (D=150mm, H=300mm) on remolded MSW specimens. General observations depict that with an increase in strain level, loading rises without any peak point on stress-strain curves. Fresh samples represent the lowest shear strength followed by 21, 14 and 5.5 year-old samples respectively. There is a direct relationship between fiber content and shear strength. Internal friction angle of aged samples decreases in comparison with fresh ones while cohesion has an inverse trend and rises over the time. According to the effect of burying condition on MSW characteristics, it seems that DOD factor is a more appropriate factor than age in order to analyze long-term behavior of MSW.
Dr M. Khodaparast, Dr A.m. Rajabi, Mr. M. Mohammadi,
Volume 13, Issue 2 (6-2015)

The Dynamic Probe is an effective tool used in site investigation. It is more economic than the use of direct drilling, particularly in explorations with moderate depth. This paper presents an experimental study to investigate the capability of using dynamic probing to evaluate the shear strength and compaction percent of fine soil. A series of dynamic probe tests were carried out at 6 different sites in the Khozestan, Hormozgan and Qom provinces in the central and southern regions of Iran. The repeatability of the results is considered and new empirical equations relating the dynamic point resistance to undrained shear strength and compaction percent are proposed. For undrained shear strength evaluation of fine soils, i.e. clay and silty clay soils, a reliable site-specific correlation between qd and Cu can be developed when considering the correlation between log qd and log Cu. Also compaction present can be evaluated by qd. These equations can be developed to provide site-specific relationships based upon geotechnical data at each new location. Using this approach an estimation of the undrained shear strength Cu and compaction percent CP can be determined from dynamic probe tests with acceptable accuracy. The present paper also encourages the wider application of dynamic probing for site investigation in fine soils.
Omar Al Hattamleh,
Volume 14, Issue 2 (3-2016)

ABSTRACT The influence of the sand placement method above geotextile layer on interface shear strength behavior was investigated. Seven different types of woven and non woven geotextile were used with only poorly graded sand. The investigation involved placement of sand layer through inclined horizontal plane with different angles. This step constitutes a fundamental step for assessing soil to be deposited in different plane and therefore with different internal soil fabric. The interface shear strength was evaluated by using direct shear test. Although the investigated soil is uniform poorly graded sand, the influence of the deposit plane was significant especially for nonwoven geotextile. Differences in soil interface shear strength associated with the tested geotextiles samples shows that samples with higher mass per unit area and same opening sizes had the higher interface friction angle regardless the bedding plane. Influence of bedding plane on interface modulus of elasticity which used in most of interface modeling was investigated using Janbu’s formula. It is noted that the use of secant interface modulus of elasticity at 1% strain and at 50% of peak stresses gave a consistent prediction of n and Ku constant appear in Janbu’s formula for all types of geotextile. The above results were reflected in the prediction for interface molded such as Chen and Juran as shown. Therefore, the existing interface modeled is needed to be modified to account for the method that the sand is being placed above the geotextile layer.

Guray Arslan, Muzaffer Borekci, Muzaffer Balci, Melih Hacisalihoglu,
Volume 14, Issue 3 (4-2016)

The contribution of concrete to inelastic deformation capacity and shear strength of reinforced concrete (RC) columns failing in shear has been investigated extensively by various researchers. Although RC members are designed to have shear strengths much greater than their flexural strengths to ensure flexural failure according to the current codes, shear degradation of RC columns failing in flexure has not been studied widely. The aim of this study is to investigate the shear degradation of RC columns using finite element analyses (FEA). The results of FEA are compared with the results of experimental studies selected from literature, and it is observed that the lateral load-deflection curves of analysed columns are compatible with the experimental results. Twenty-six RC columns were analysed under monotonically increasing loads to determine the concrete contribution to shear strength. The results of analyses indicate that increasing the ratio of shear to flexural strength reduces the concrete contribution to shear strength of the columns.

Hossein Soltani-Jigheh,
Volume 14, Issue 7 (10-2016)

The main objective of present study is to possible use of plastic waste materials for reinforcing clayey soils. An experimental study was planned to investigate compressibility and undrained shear behavior of clayey soil mixed with plastic waste. The mixtures were prepared with various amount of plastic waste (i.e. 0%, 0. 5%, 1.0%, 1.5% and 3.0% in dry weight) and interactive effect of plastic waste, plastic flexibility, confining pressure and initial density on the behavior of clayey soil was studied by performing compaction, consolidated undrained triaxial and oedometer consolidation test. The results show that plastic wastes do not affect compaction characteristics of clayey soil considerably and adding them to the clay more than a specific value (i.e. 1.0% in this research) causes to change undrained behavior of samples from contractive to dilative. In addition, beyond this specific value, it improves shear strength and reduces compressibility of clay. The rate of increase in shear strength and decrease in compressibility depends on the confining pressure, flexibility of plastic and initial density of samples. It is more noticeable when plastic waste in mixtures is relatively rigid and density and confining pressure are high. Moreover, plastic waste has a negative effect on the free swelling, swelling pressure and swelling index of samples, so that these parameters for plastic waste mixed clay are higher than the associated values of plain clay.

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