Rotational Multiple Yield Surface Framework Research Articles

PREDICTION OF SOIL SETTLEMENT ON SOFT CLAY SOIL USING NORMALIZED ROTATIONAL MULTIPLE YIELD SURFACE FRAMEWORK (NRMYSF)

Soft clays are highly compressible, high-water content, low shear strength, and have poor permeability, which result in significant settlement under long-term loads. Therefore, one of the most challenging geotechnical engineering problems is to predict the settlement from soft clay soil. Normalized Rotational Multiple Yield Surface Framework (NRMYSF) is developed from the soil stress-strain behaviour and shear strength characteristic. It is able to estimate the stress-strain curve for shear strength in triaxial tests. The consolidated drained (CD) triaxial tests and conventional 1-dimensional consolidation of oedometer has been conducted on soft clay soil. The settlement soil prediction was compared between the NRMYSF and conventional 1-dimensional consolidation under Terzaghi’s principle. The NRMYSF prediction model was smaller than the conventional oedometer by 0.1459m to 0.1431m for Sample A, and by 0.1890m to 0.1398m for Sample B. Therefore, this method has the potential to predict the settlement of soft clay soils.

Prediction of Stress-Strain Response Using Rotational Multiple Yield Surface Framework in Malaysian Residual Soil

Soil settlement is normally quantified using conventional soil volume change models which are solely based on the effective stress and the role of shear strength is ignored due to the difficulties to incorporate in the framework. The Rotational Multiple Yield Surface Framework (RMYSF) is a soil volume change model developed from the standpoint of the interaction between the effective stress and shear strength. RMYSF incorporates the development of mobilised shear strength within the body of the soil whenever the soil is subjected to anisotropic compression. Currently the framework has been applied to predict the soil anisotropic stress-strain behaviour at any effective stress. This paper present the enhancement of this volume change framework using normalisation of axial strain with the understanding that the failure axial strain is not unique, but increases as the effective stress increases. This technique has essentially produced a better accuracy in the prediction of the stress-strain response for Malaysian residual soils. A series of drained tri-axial tests under various effective stresses has been conducted using specimens of 50mm diameter and 100mm height and from the stress-strain curves the inherent mobilised shear strength envelopes at various axial strains have been determined. These mobilised shear strength envelopes were then applied for the prediction of the soil stress-strain response. An excellent agreement between the predicted and the actual stress-strain curves has been achieved.

Collapse behavior of unsaturated remolded granitic residual soil

In the tropical area, most shallow foundations and embankments are involved in dealing with unsaturated soils. Any collapse or settlement in unsaturated soils is determined by two independent stress variables: the applied stress and suction. The massive collapse related to suction changes may lead to unrecoverable damages to compacted earth fills both economic and human loss while this collapse has not been seen in the design. The aim of this study was to investigate the influence of stress states and matric suction on collapse behavior of an unsaturated Malaysian granitic residual soil grade V. A suction-controlled double wall triaxial test was carried out to obtain the axial strain of the compacted specimen during loading and wetting collapse. In addition, there has been an attempt to predict the collapse behavior of the soil by using Rotational Multiple Yield Surface Framework (RMYSF). During loading in imposed suction, the axial strain increased as deviator stress increased. When the soil was inundated and the imposed suction was decreased step by step down to zero, the axial strain was very small at suction close to residual suction. It gradually increased as suction decreased. A massive settlement around 1.92% of the initial height was observed while the soil was nearly saturated. The findings also proved that the RMYSF model is able to predict the collapse behavior of the tested soil sufficiently.

Strain Softening Prediction Using Normalized Method

This study assessed the applicability of normalized method in predicting the stress-strain curve at the strain softening phase. The methodology is based on standard test and easily replicable which is conventional triaxial test. The soil sample from Kuala Terengganu, Malaysia was taken for the test. The drained triaxial test was conducted on four samples with various effective stresses (50, 100, 200 and 300kPa). The results showed that the soil is classified as silty clay with high plasticity. Based from the results, the stress-strain curves indicate strain softening clearly. The normalized method is applied in this study. It is based from Rotational Multiple Yield Surface Framework (RMYSF). However, RMYSF is applied to predict the stress-strain curves for unsaturated soil and limited to strain hardening only. Extension work is conducted to the existing method by predicting the strain softening phase for saturated soil. It can be concluded that normalized method is successfully predicted the strain softening phase of the soil. The main advantage of this method is that it can be applied to predict the soil strength parameter for various effective stresses without having to conduct many tests. Therefore, this method will help to cut the time and cost of testing effectively.

Soil anisotropic stress-strain prediction using Normalised Rotational Multiple Yield Surface Framework (NRMYSF) for compacted tropical residual sandy soils

Rotational Multiple Yield Surface Framework (RMYSF) is an anisotropic soil volume change model developed to integrate shear strength in characterising the soil volume change behaviour from the standpoint of the stress-strain response. The anisotropic soil volume change behaviour is described from the interaction between applied stress represented by the Mohr-Coulomb circle and shear strength in terms of curved-surface mobilized shear strength envelope. This research work is to enhance the current method of RMYSF using normalisation of axial strain to predict stress-strain behaviour. A series of triaxial tests has been conducted on Malaysian sedimentary sandy residual soil grade VI. The stress-strain curves and volume change behaviours were analysed using this enhanced method. Subsequently, the enhance method is apply to predict the soil stress strain respond and make comparison with the actual laboratory stress-strain curve. Essentially the normalised method of RMYSF has improved the accuracy of the prediction as presented in the paper.

Prediction of Soil Anisotropic Stress-Strain Behaviour Incorporating Shear Strength Using Improvise Normalised Stress-Strain Method

Currently the soil anisotropic stress-strain behaviour can be predicted accurately at any effective stress using the Rotational Multiple Yield Surface Framework. This framework incorporates the developed of mobilised shear strength within the body of the soil mass whenever the soil is subjected to anisotropic compression. However the accuracy of the framework can be improvised since the failure axial strain is not unique but increases as the effective stress increases. This improved method s call normalised strain method. This method is applied to predict the stress-strain behaviour of granitic residual soil grade V from Kuala Kubu Baharu. The improve accuracy of this method will be presented in comparison with the conventional method.

Normalized Rotational Multiple Yield Surface Framework (NRMYSF) stress-strain curve prediction method based on small strain triaxial test data on undisturbed Auckland residual clay soils

Small strain triaxial test measurement is considered to be significantly accurate compared to the external strain measurement using conventional method due to systematic errors normally associated with the test. Three submersible miniature linear variable differential transducer (LVDT) mounted on yokes which clamped directly onto the soil sample at equally 120° from the others. The device setup using 0.4 N resolution load cell and 16 bit AD converter was capable of consistently resolving displacement of less than 1µm and measuring axial strains ranging from less than 0.001% to 2.5%. Further analysis of small strain local measurement data was performed using new Normalized Multiple Yield Surface Framework (NRMYSF) method and compared with existing Rotational Multiple Yield Surface Framework (RMYSF) prediction method. The prediction of shear strength based on combined intrinsic curvilinear shear strength envelope using small strain triaxial test data confirmed the significant improvement and reliability of the measurement and analysis methods. Moreover, the NRMYSF method shows an excellent data prediction and significant improvement toward more reliable prediction of soil strength that can reduce the cost and time of experimental laboratory test.

Stress-Strain response of Malaysian granitic residual soil grade V, according to Rotational Multiple Yield Surface Framework

In soil mechanics characterizing the soil volume change behavior is based on the effective stress concept. Conventional soil settlement models which have been developed by this principle, are empirical in nature and being verified against experimental or field observations. However, they are not still able to explain and formulate some unusual soil volume change behaviors such as wetting collapse by this concept. The consequence of shear strength in the interaction of effective stress should be integrated into volume change frameworks in such cases in order to puzzle out these weird behaviors. The principle has been incorporated in an anisotropic soil settlement model know as Rotational Multiple Yield Surface Framework (RMYSF). The framework has been developed from the standpoint of the soil stress-strain response within anisotropic stress condition. The anisotropic soil volume change behavior is described from the interaction between applied stress (presented by the Mohr-Coulomb circle) and shear strength (in terms of curved-surface mobilized shear strength envelope). The applicability of the model has been examined for limestone gravel from the United Kingdom and granitic residual soil grade VI from Kuala Kuba Baru, Malaysia before, however still needs to be tested for another kind of soils. In this paper, a series of triaxial tests were conducted on Malaysian granitic residual soil grade V, in saturated and unsaturated condition. The stress-strain curves and volume change behavior of the soil were obtained from laboratory test results. Besides that, the stress-strain response of the soil has been predicted using RMYSF framework. The predicted stress-strain curves were compared with the test result and the accuracy of the framework was examined. The obtained and predicted curves had a fairly good match.