Laboratory Studies of Small Strain Stiffness and Modulus Degradation of Warsaw Mineral Cohesive Soils

The shear modulus and normalized shear modulus degradation curve are the fundamental parameters describing soil behavior. Thus, this article is focused on the stiffness characteristic of 15 different Warsaw cohesive soli represented by the parameters mentioned above. In this research, standard resonant column tests were performed in a wide shear strain range, from a small one, where soil behaves like an elastic medium, to a medium one, where soil has an unrecoverable deformation. Collected data allows the authors to create empirical models describing stiffness characteristics with high reliability. The maximum shear modulus calculated by the proposed equation for Warsaw cohesive soil had a relative error of about 6.8%. The formula for normalized shear modulus estimated G/GMAX with 2.2% relative error. Combined empirical models for GMAX, and G/GMAX allow the evaluation of Warsaw cohesive soil’s shear modulus value in a wide shear deformation range, with a very low value of the relative error of 6.7%.

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Small strain stiffness in overconsolidated Pliocene clays

Annals of Warsaw University of Life Sciences – SGGW Land Reclamation ◽

10.2478/sggw-2013-0014 ◽

2013 ◽

Vol 45 (2) ◽

pp. 169-181 ◽

Cited By ~ 2

Author(s):

Katarzyna Markowska-Lech ◽

Mariusz Lech ◽

Marek Bajda ◽

Alojzy Szymański

Keyword(s):

Shear Modulus ◽

Shear Wave ◽

Wave Velocity ◽

Shear Wave Velocity ◽

Cohesive Soil ◽

Small Strain ◽

Soil Parameters ◽

Small Strain Stiffness ◽

Triaxial Apparatus ◽

Triaxial Cell

Abstract Small strain stiffness in overconsolidated Pliocene clays. A huge development of technical infrastructure, including the construction of many high-rise buildings, roads, railroads and extension of subway lines, took place over the recent years in Poland. Therefore, numerous planned investment projects require geotechnical data documenting the variation of soil parameters found in the subsoil. The shear wave velocity is one of the most important input parameters to represent the stiffness of the soil deposits. This paper focuses on the methods and devices using measurements of the shear wave velocity to estimate the initial shear modulus in cohesive soil. It is preferable to measure VS by in situ wave propagation tests, however it is often economically not feasible in all regions of Poland. Hence, a reliable correlation between shear wave velocity and parameters measured in triaxial cell or static penetration parameters would be a considerable advantage. This study shows results obtained from the bender elements tests and field techniques - seismic cone penetration test and seismic flat dilatometer, performed on overconsolidated cohesive soils in Warsaw. On the basis of the test results possible correlations between shear wave velocity (initial shear modulus), mean effective stress and void ratio are considered and four original empirical relationships are proposed. Moreover, the proposed formulas by two different techniques using triaxial apparatus and also RCPT cone were examined. The proposed formulas show a reasonable agreement with direct shear wave velocity profiles for clays and might be incorporated into routine laboratory and field practice

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Simple shear testing of sensitive, very soft offshore clay for wide strain range

Canadian Geotechnical Journal ◽

10.1139/t09-059 ◽

2009 ◽

Vol 46 (11) ◽

pp. 1277-1288 ◽

Cited By ~ 12

Author(s):

G. Lanzo ◽

A. Pagliaroli ◽

P. Tommasi ◽

F. L. Chiocci

Keyword(s):

Shear Modulus ◽

Simple Shear ◽

Damping Ratio ◽

Soft Clay ◽

Strain Range ◽

Small Strain ◽

Cyclic Shear ◽

Wide Range ◽

Equivalent Shear Modulus ◽

Two Stages

Stiffness and damping properties of sensitive, very soft clay sediments of the Italian Adriatic continental shelf are determined by means of two series of cyclic simple shear tests (one with 12 stages and one with two stages). The apparatus used in this research is capable of investigating the stress–strain behaviour of the soil in a wide range of shear strains from about 0.0004% to 1%. Test results were expressed in terms of small-strain shear modulus (G0), normalized equivalent shear modulus (Geq/G0), and damping ratio (D) versus cyclic shear-strain amplitude (γc). These parameters were analyzed in the framework of existing literature by comparison with empirical correlations developed for onshore materials of different plasticity and, limited to G0, also for soft soils. The dependence of G0, Geq/G0–γc, and D–γc on factors such as void ratio, stress history, and loading cycles is analyzed and discussed.

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Study on the Small-Strain Behaviors of Unsaturated Soils

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.353-356.1097 ◽

2013 ◽

Vol 353-356 ◽

pp. 1097-1100

Author(s):

Jin Xing Wang ◽

Wei Min Liang ◽

Yong Qiang Yu

Keyword(s):

Unsaturated Soils ◽

Strain Range ◽

Cohesive Soil ◽

Small Strain ◽

Degree Of Saturation ◽

Factors Affecting ◽

Triaxial Apparatus ◽

Ground Deformations ◽

Non Linear ◽

Precise Prediction

Non-linear stress-strain characteristics and strain dependency of stiffness of saturated soils at small strain level have been reported by many researchers. However, the non-linear stiffness of unsaturated soils is not fully studied. The aim of this study is to clarify main factors affecting the non-linear stiffness of unsaturated soil at small strain range for a precise prediction of various ground deformations. Experiments were conducted with both sand and cohesive soil, by using a triaxial apparatus developed for small strain measurement. As the important factors for mechanical behaviour of unsaturated soils under small strain range, the effects of suction and mean net stress, which introduce the decrease of void ratio and degree of saturation, were discussed in the study.

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Threshold Shear Strain for Dynamic Ramberg-Osgood Model in Soils Based on Thermomechanics

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1065-1069.255 ◽

2014 ◽

Vol 1065-1069 ◽

pp. 255-259

Author(s):

Xiao Xia Guo ◽

Xiang Sun

Keyword(s):

Friction Coefficient ◽

Shear Modulus ◽

Shear Strain ◽

Dynamic Characteristics ◽

Fundamental Property ◽

Small Strain ◽

Dissipation Function ◽

Dynamic Shear Modulus ◽

Soil Behavior ◽

Skeleton Curve

The threshold shear strain is a fundamental property of the soil behavior subjected to cyclic loading. Starting from the unloading and reloading hysteretic curves of dynamic Ramberg-Osgood model, construct small-strain dynamic dissipation function and explain small-strain dynamic characteristics by use of the skeleton curve back stress assumption. The plotting results of yield curves in true stress space indicate that there exist two threshold shear strains which are defined as the first threshold shear strain and the second threshold shear strain respectively which represent boundaries between fundamentally different dynamic characteristics of cyclic soil behavior. The yields of soil are controlled by the constant friction coefficient, the variable friction coefficient and dilatancy-related microstructural changes respectively. Both the first threshold shear strain and the second threshold shear strain do depend significantly on the maximum dynamic shear modulus coefficient and exponent. Comparison between the two threshold shear strain values and shear modulus reduction curves obtained on exactly the same soils confirms that the soil behavior is considerably at nonlinear at , the secant shear modulus,Gs, of the four soils studied is between 0.6 and 0.8 of its maximum value.

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Optimizing modified triaxial testing for small strain zone using local displacement transducers and bender element for cement-treated soft soil

E3S Web of Conferences ◽

10.1051/e3sconf/202133103003 ◽

2021 ◽

Vol 331 ◽

pp. 03003

Author(s):

Muhammad Akmal Putera ◽

Noriyuki Yasufuku ◽

Adel Alowaisy ◽

Ahmad Rifai

Keyword(s):

Shear Modulus ◽

Soft Soil ◽

Strain Range ◽

Small Strain ◽

Secant Modulus ◽

Bender Element ◽

Treated Soil ◽

Local Displacement ◽

Settlement Behavior ◽

Bender Element Test

The settlement behavior is a common problem on the railway structure that can be optimized by applying cement-treated soil as ground restoration. However, the application of a high cement mixing content needs a proper estimation that can be achieved by adjusting the element testing. The strain measurement devices can estimate the deformation characteristics, such as secant modulus, Poisson ratio, and shear modulus that can describe the settlement behavior and stiffness of cement-treated soil. This research is focused on a static analysis of triaxial consolidated undrained (CU¯) testing that is improved by the axial and radial local displacement transducer (LDT) and bender element to increase the accuracy of measurement results. Furthermore, the secant modulus and shear modulus is more accurate when the combination of radial and axial LDT is used due to a small strain range. Lastly, the shear modulus measurement is improved by using a filler in the cement-treated soil for the bender element test. To conclude, this system of testing for the static condition can be utilized for the dynamic condition, because the measurement shows a reliable result for a small strain range which is the parameter of the dynamics condition.

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ANALYSIS OF THE ERROR IN DETERMINING THE EQUIVALENT SIZE OF A DEFECT BY THE STANDARDLESS METHOD DURING ULTRASONIC TESTING

Kontrol Diagnostika ◽

10.14489/td.2021.04.pp.050-057 ◽

2021 ◽

pp. 50-57

Author(s):

A. N. Kireev ◽

M. A. Kireeva

Keyword(s):

Relative Error ◽

High Reliability ◽

Ultrasonic Method ◽

Experimental Studies ◽

Standard Samples ◽

Defect Identification ◽

Identification Method ◽

Maximum Value ◽

Software Product ◽

The Relationship

The article provides a review and analysis of the defect identification method for determining the size of discontinuities when diagnosing various machine parts and units by the manual ultrasonic method. This method makes it possible to determine the equivalent size of discontinuities of various types without using standard samples of an enterprise: point planar and volumetric; extended planar and volumetric. The method is based on the use of the relationship between the amplitude and time characteristics of the echo signal from the discontinuity and the backside signal in the object being diagnosed and the equivalent size of the discontinuity. The article presents the mathematical apparatus for the implementation of this method. Also presented is a software product that allows you to automate calculations when using this defect identification method. The article contains experimental studies of the method for determining the equivalent dimensions of discontinuities of various types, which have shown its high reliability. The maximum value of the relative error in determining the equivalent size of a point planar discontinuity was 2.867 %. The maximum value of the relative error in determining the equivalent size of a point volumetric discontinuity was 1.986 %. The maximum value of the relative error in determining the transverse equivalent size of an extended planar discontinuity was 0.667 %. The maximum value of the relative error in determining the transverse equivalent size of an extended volumetric discontinuity was 1.95 %.

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