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The unique behaviour of carbonate materials under shear loading has stimulated in investigating of their geological and engineering properties.Carbonate soils composed of calcium or other carbonates and most abundant in tropical marine environments are of interest from geotechnical view, especially for offshore engineers engaged with Fossil-based fuel exploitation. This was initiated in the early 1960's, when the first offshore borings in the Persian Gulf identified layers of calcarenite and thick layers of sand containing visible shell fragments.For the purpose of exploiting gas and oil resources in hot and temperate climates (e.g. Persian Gulf) off-shore structures have been placed on carbonate soils. The carbonate sediments are high crushable compared with low crushable sediments such as quartzic soils.To examine the crushability of these problematic sediments a series of monotonic compression, extension and post-cyclic triaxial tests under different densities and confining pressures was carried out to study the crushing behaviour of "Rock" carbonate sand obtained from Cornwall, England.It was shown that crushing coefficient decreases with increasing in maximum principal effective stress ratio for both loose and dense states. It seems that for skeletal carbonate sand maximum and minimum dry densities will be changed during shearing loading. In other words, even though the sample has experienced an increase in density, it may also have experienced a reduction in relative density.

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This paper presents the results of a series of monotonic and post-cyclic triaxial tests carried out on a clay specimen and three types of clay-sand mixed specimens. The focus of the paper is on the post-cyclic mechanical behavior of the mixed specimens, as compared to their monotonic behavior. Analyses of the tests results show that cyclic loading degrade undrained shear strength and deformation modulus of the specimens during the post-cyclic monotonic loading. The degradation depends on the sand content, the cyclic strain level and to some degrees to the consolidation pressure.

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The present paper is devoted to a new critical state based plasticity model able to predict drained and undrained behaviour of

granular material. It incorporates a bounding surface plasticity model describing in multilaminate framework to capitalize on

advantages of this mathematical framework. Most of the models developed using stress/strain invariants are not capable of

identifying the parameters depending on directional effects such as principal stress rotation and fabric this is mainly because

stress/strain invariants are scalar quantities. The principal features of this model can be postulated as considering both inherent

and induced anisotropy, principal stress rotation. Since the local instability of saturated sand within post-liquefaction is highly

dependent on the residual inherent/induced anisotropy, bedding plane effects and also the stress/strain path the new mode is

competent to be employed in this regard. The constitutive equations of the model are derived within the context of non-linear

elastic behaviour for the whole medium and plastic sliding of interfaces of predefined planes. As follows, the constitutive

equations are described in detail and then the experimental results and sensitive analysis of key material constants are shown

which all imply the power of the model in predicting of soil behaviour under any condition in soil structures.

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In a rare engineering experience throughout the world, we successfully stabilized relatively coarse materials of drain using

cement grouting. The grouting work was performed at the Karkheh earth dam, southwest Iran, and was part of the efforts to

extend the dam’s cut-off wall. Since the dam was completed, the execution of the new cut-off wall from the dam crest was

inevitable. Hence, one of the main difficulties associated with the development of the new cut-off wall was trenching and execution

of plastic-concrete wall through the relatively coarse materials of drain in the dam body. Due to high permeability of drain, the

work was associated with the possible risk of excessive slurry loss which could result in the collapse of the trench. In order to

achieve an appropriate grouting plan and to determine the mix ratio for the grouting material, a full-scale test platform consisting

of actual drain materials was constructed and underwent various tests. Results of the testing program revealed that a grouting

plan with at least 2 grouting rows and a Water/Cement mix ratio of 1/ (1.5-2) can successfully stabilize the drain materials. After

finalizing the technical characteristics of the grouting work, the method was applied on the drain materials of the Karkheh dam

body. The results were satisfactory and the drain materials were stabilized successfully so that the cut-off wall was executed

without any technical problem.

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The ground improvement using Plastic Board Drain (PBD) in soft soil was undertaken by sand mat formation, PBD installation, preloading surcharge, and removal of surcharge. During this procedure, the sand mat formation induced an initial settlement. However, it was very difficult to estimate that settlement due to PBD installation, which frequently destroyed the instruments installed in the ground. Consequently, the initial settlement was not properly included in total settlement. In this study, the initial settlement was estimated using ground level measurement and cone penetration test. Both predicted almost the same amount of initial settlement. The initial settlement is linearly increased with the depth of the sand mat. The degree of consolidation and the time of surcharge removal were estimated using the settlement included the initial settlement. Correct estimation of initial settlement is very important because it is a critical factor, which affects total settlement and the time of surcharge removal. If the initial settlement is not considered, the preloading surcharge may be overloaded or the time of surcharge removal may be predicted incorrectly. Consequently, the prediction of settlement, which requires to management of construction procedure of the project, may be wrong

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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.

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Upstream blankets, drains and cutoff walls are considered as effective measures to reduce seepage, uplift pressure and exit gradient under the foundation of hydraulic structures. To investigate the effectiveness of these measures, individually or in accordance with others, a large number of experiments were carried out on a laboratory model. To extend the investigation for unlimited arrangements, the physical conditions of all experiments were simulated with a mathematical model. Having compared the data obtained from experiments with those provided from the mathematical model, a good correlation was found between the two sets of data indicating that the mathematical model could be used as a useful tool for calculating the effects of various measures on designing hydraulic structures. Based on this correlation a large number of different inclined angles of cutoff walls, lengths of upstream blankets, and various positions of drains within the mathematical model were simulated. It was found that regardless of their length, the blankets reduce seepage, uplift pressure and exit gradient. However, vertical cutoff walls are the most effective. Moreover, it was found that the best positions of a cutoff wall to reduce seepage flow and uplift force are at the downstream and upstream end, respectively. Also, having simulated the effects of drains, it was found that the maximum reduction in uplift force takes place when the drain is positioned at a distance of 1/3 times the dam width at the downstream of the upstream end. Finally, it was indicated that the maximum reduction in exit gradient occurs when a drain is placed at a distance of 2/3 times of the dam width from upstream end or at the downstream end.

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This paper investigates the time dependent behaviour of Sunshine embankment on soft clay deposit with and without prefabricated vertical drains. An elasto visco-plastic model was used to investigate the influence of anisotropy and creep effect on the settlement behaviour of the embankment. The constitutive model, namely ACM accounts for combined effects of plastic anisotropy and creep. For comparison, the problem is also analysed with isotropic Modified Cam Clay model which does not consider creep effect. To analyse the PVD-improved subsoil, axisymmetric vertical drains were converted into equivalent plane strain conditions using two different mapping approaches. The results of the numerical analyses are compared with the field measurements. The numerical simulations suggest that the anisotropic creep model is able to give a better representation of soft clay response under an embankment loading. The isotropic model which neglects effects of anisotropy and creep may lead to inaccurate predictions of soft clay response. Additionally, the numerical results show that the mapping method used for PVD improved soft clays can accurately predict the consolidation behaviour of the embankment and provide a useful tool for engineering practice.

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The behavior of Chamkhaleh sand and three other recognized sands namely, Babolsar, Firouzkuh and Standard (Ottawa) sands are compared using triaxial apparatus under undrained monotonic loading conditions. Chamkhaleh and Babolsar sands are supplied naturally from southern Caspian Sea shorelines, whereas artificial Firouzkuh and Standard sands were supplied commercially. Samples were prepared using wet tamping with regard to the reduced compaction effect at relative density of 15% under isotropic consolidation pressures of 100, 300 and 500 kPa. The results of triaxial tests have indicated that Chamkhaleh sand has much more dilation tendency than the other sands. In order to evaluate the reasons behind this behavior, the spherecity and roundness of all the four sand particles were measured using an image processing method. It was revealed that the spherecity of the four sands is not much different, but Chamkhaleh sand is more angular than the other sands. For comparison of the dilative response of the sands in undrained triaxial tests, a “dilation tendency index” is introduced. This index may be used as a criterion for measuring the dilation of sands in undrained tests. Results have shown that the internal friction angle under the steady state condition is more dependent on the shape of particles than the maximum strength condition. For spherecities greater than 0.5, the dependency rate of sand behavior on the roundness is decreased.