Characterization of soft soil using multi-channel analysis of surface waves (MASW) and electrical resistivity method (ERM)

This thesis demonstrates the research on the soft soil characteristics using geophysical methods. The need on non-intrusive, time efficient, economic and larger volume of investigation had increased the demand of using geophysical methods for geotechnical investigation. The research concentrates on the determination of soft soil shear-wave velocity (Vs) profile using the multi-channel analysis of surface waves (MASW) and the soil stratigraphy using Electrical Resistivity Method (ERM). The soft soil Vs and stratigraphy were determined and correlated with the peat sampler and borehole data to obtain more accurate data. The research was conducted at Parit Nipah and RECESS UTHM. The Vs obtained for peat and soft clay at Parit Nipah was in the range of 29.7 to 34.9 m/s and 36.8 to 76.9 m/s respectively. While, the soft clay Vs obtained at RECESS was in the range of 64.4 to 124.0 m/s. The lower Vs obtained on peat compared to soft clay was due to the heterogeneity of peat. The soil strata obtained by ERM had good agreement with the peat sampler and borehole data. The resistivity value of peat and soft clay obtained at Parit Nipah was in the range of 47.2 to 127.7 ohm.m and 9.4 to 25.8 ohm.m correspondingly. While, at RECESS soft clay, the resistivity value was in the range of 1.0 to 4.6 ohm.m. The lower resistivity value of soft clay was governed by the amount of clay fraction which was related to cation exchange capacity (CEC). As higher CEC results in higher conductivity. The relationship obtained between the 1-D Vs and 1-D resistivity value shows that consistent value of peat Vs was followed by the slight decrease in peat resistivity value. While, drastic increase in soft clay Vs results in a significant decrease in soft clay resistivity value. This concluded that stiffness does not produce significant effect on the soil resistivity. Overall, MASW and ERM produced high quality data for subsurface investigation in larger volume with timely efficient manner and more economic

Study on the Rheological Properties and Constitutive Model of Shenzhen Mucky Soft Soil

In order to obtain the basic parameters of numerical analysis about the time-space effect of the deformation occurring in Shenzhen deep soft-soil foundation pit, a series of triaxial consolidated-undrained shear rheology tests on the peripheral mucky soft soil of a deep foundation pit support were performed under different confining pressures. The relations between the axial strain of the soil and time, as well as between the pore-water pressure of the soil and time, were achieved, meanwhile on the basis of analyzing the rheological properties of the soil, the relevant rheological models were built. Analysis results were proved that the rheology of Shenzhen mucky soft soil was generally viscous, elastic, and plastic, and had a low yield stress between 90 and 150 kPa. The increase in pore-water pressure made the rheological time effect of the mucky soft soil more remarkable. Thus, the drainage performance in practical engineering should be improved to its maximum possibility extent to decrease the soft-soil rheological deformation. Lastly, a six-component extended Burgers model was employed to fit the test results and the parameters of the model were determined. Findings showed that the extended Burgers model could satisfactorily simulate the various rheological stages of the mucky soft soil. The constitutive model and the determination of its parameters can be served as a foundation for the time-space effect analysis on the deformation of deep soft-soil foundation pits

Numerical Investigation of Dynamic Pipe-Soil Interaction on Electrokinetic-Treated Soft Clay Soil

© 2019 American Society of Civil Engineers. Researchers have underscored the importance for a pipeline to safeguard against adverse effects resulting from its displacement in the vertical, axial, and lateral directions because of the low shear strength of the soil. The seabed may sometimes consist of soft or very soft clay soil with high water content and low shear strength. Dissipation of the water content from the soil void increases its effective stress, with a resultant increase in the soil shear strength. The electrokinetic (EK) concept has been applied to increase soil bearing capacity with barely any study conducted on its possible application on pipe-soil interaction. The need to explore more options merits further research. The EK process for the pipe-soil interaction consists of two main stages: the electroosmotic consolidation process and dynamic analyses of the pipe-soil interaction. The present study numerically investigated the impact of EK-treated soil on pipe-soil interaction over the non-EK process. The results of dynamic pipe-soil interaction on EK-treated soil when compared with non-EK-treated soil indicate a significant increase in the force required to displace a pipeline

Mechanical properties of soft clay stabilized with cement-rice husks (RH)

Chemical stabilization has been extensively used for the improvement of soft clay soils, in enhancing the shear strength and limiting the deformation behaviours. Cement is widely used as a stabilizing material for soils, but the increasing price is causing economic concerns among practitioners and clients alike. The quest for alternative cheaper stabilizing agents is therefore more urgent than before. Rice husk is a major agricultural waste in Malaysia and the common disposal method of open burning has notoriously contributed to environmental pollution. The possibility of admixing rice husks with cement for stabilizing soft soils could be a solution to both problems. This study was aimed at assessing the usefulness of cement-rice husks as an effective soil stabilizer for improving the mechanical properties of clay soils. Laboratory experiments were carried out on a stabilized soft clay to study the inter-relationships between shear wave velocity, one-dimensional compressibility and unconfined compressive strength. Bulk clay samples were collected from the Research Centre for Soft Soils (RECESS) of UTHM. The stabilized specimens were prepared with the clay admixed with 5 % and 10 % cement and various quantities of rice husks, then compacted into cylindrical specimens measuring 38 mm in diameter and 76 mm high. The specimens were then left to cure for different periods up to a month. The stabilized specimens were observed to undergo increase in stiffness and strength, as well as significant reduction in compressibility, highlighting the great potential of cement-rice husk as an alternative soft soil stabilizer. Keywords: Clay soil stabilization, cement, rice husk, shear wave velocity, onedimensional compressibility, unconfined compressive strengt

Finite element analysis of footwear and ground interaction

Military boots are designed to prevent the soft tissue and skeletal structure of the feet from damage under heavy usage. Good slip-resistant tread patterns of the outer-sole are vital to minimise the risk or severity of slipping under demanding conditions, most likely to result in accidents. However, boot design should also offer the customer flexibility, comfort, and shock absorption, be lightweight and be able to operate regardless of the ground surface texture and various weather conditions. The issue of footwear and ground interaction investigated in this study can be classified as a traditional stability problem. Solutions to these problems are often obtained using the theory of perfect plasticity. Therefore, elastic–perfectly plastic theory was adopted in this study and the Drucker-Prager (DP) material model was chosen to model the soil properties. Literature survey showed that little studies exist on the subject of interaction between foot and soft ground, in particular, using numerical modelling methods. However, there are numerous research works on some relevant domains, such as soil–tillage tool interaction, soil–wheel interaction and soil–structure interaction, etc. A three-dimensional finite-element (FE) analysis of a subsoiler cutting with pressurised air injection was performed by employing a DP harden material model without consideration of friction force by Araya and Gao [1]. Saliba [2] undertook elastic–viscoplastic FE modelling for tire/soil interaction and Mouazen and Nemenyi [3, 4] adopted a DP model for analysing soil–tillage tool interaction

Anisotropic creep model for soft soils

In this paper a new anisotropic model for time-dependent behaviour of soft soils is presented. The formulation is based on a previously developed isotropic creep model, assuming rotated Modified Cam Clay ellipses as contours of volumetric creep strain rates. A rotational hardening law is adopted to account for changes in anisotropy due to viscous strains. Although this will introduce some new soil parameters, they do not need calibration as they can be expressed as functions of basic soil parameters through simple analytical expressions. To start with, the one-dimensional response of the model is discussed, making it possible to explore how the model is capable of capturing key features of viscous soft soil behaviour. Subsequently, the three-dimensional generalisation of the model is presented, followed by comparison with experimental data, showing good agreement in both triaxial undrained compression and extension. In the authors' opinion, the simple formulation of the model makes it attractive for use in engineering practice

The hybrid of floating stone column by numerical and physical evaluation

Rapid population growth amplifying demand for accommodation and infrastructure has resulted in soft ground being increasingly used in construction. Problems related to soft ground can be remedied by adopting a ground improvement technique. The stone column is one of the most effective and feasible techniques for soft clay soil improvement. Stone columns increase bearing capacity and reduce the settlement of soil. However, soft ground of more than 40 meters depth makes stone column treatment costlier. The design of floating stone columns within soft ground is sometimes needs to adopt. However, this method is not popular compared to the end bearing stone columns due to low mobilised shear resistance and resulted in higher occurrence of punching failure. This research is aimed for addressing the shortcoming floating stone columns with proposing the hybrid dimension floating stone columns. The hybrid stone column size able to increase the mobilised shear resistance, decrease punching failure, and reduce the volume of aggregates. In the present work, finite element analysis was performed using the program PLAXIS 2D. An elastic-perfectly plastic constitutive soil model relation based on the Mohr-Coulomb criterion was utilized to predict the behaviour of soft clay strengthen by stone column. Response Surface Methodology (RSM) was used to optimize the hybrid stone column size with the Design-Expert 6.0.4 software. The laboratory physical model tests were performed based on the sizes of optimum hybrid stone column size proposed by RSM. The results revealed that the optimal parameter of the uniform diameter of 44 mm with a length of 100 mm increases its load bearing capacity of 3260.7 N and the lowest settlement was recorded at a diameter of 24.2 mm with a length of 400 mm to achieve 25.8 mm of settlement. Moreover, the hybrid column size i.e. the first stone column diameter of 43 mm and second diameter of 21.2 mm with the same lengths of 200 mm each diameter able to achieve load-bearing capacity of 3350.9 N and settlement of 24.5 mm. Thus, by comparing with the uniform diameter stone column of 44 mm and length of 400 mm, the hybrid column able to increase the load bearing capacity by 3% and decrease the settlement by 5%. In addition, a good agreement was obtained between the numerical and physical models with variation 25%. In addition, the hybrid stone column size is able to reduce the volume of aggregates up to 40%

Pemanfaatan Limbah Sabut Kelapa Sawit Intuk Meningkatkan Kekuatan Tanah

Soil has a very significant role in construction works, both as the main composition and supporting material. If the construction is build on a soft soil like soft clay, then it will give problem to the construction building. To increase the strength of soil, soil stabilization is done by adding palm pulp fibers into the soil. In this study, the percentages of palm pulp fibers mixed are 1,5%, 2,5%, 3,5%, and 4,5% out of soft clay dry weight. To know the strength of soil, direct shear test and unconfined compressive strength (UCS) test. The mixing of palm pulp fibers affects the value of Soil Shear Strength (s) and Unconfined Compressive Strength (qu). On the level of 4,5%, the Soil Shear Strength (s) and Unconfined Compressive Strength (qu) have the biggest value. The Soil Shear Strength (s) of 129,748 kN/m2 showed a rise of 537,083% in unmixed soil, while the Unconfined Compressive Strength of 34,254 kN/m2 showed a rise of 79,048% in undisturbed soil