Category Archives: Unsaturated soil mechanics

Climate change effect on stiffness behavior of Lateritic Soil Treated with Ordinary Portland Cement

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Malaysia has used residual tropical soil (laterite soil) as a fill material for construction development. Besides that, about 25% of the total road network in Malaysia is unpaved roads whereby most of the unpaved roads use laterite soil as subgrade due to good engineering properties. However, the huge quantity of fine-grained particles in some lateritic soil exhibits poor engineering qualities and is considered problematic soil by engineers. Annually, several sections of the country have endured flooding and scorching weather. The occurrence caused extensive damage, particularly to the road structure. For example, during the dry season, the suction created has had a substantial impact on the permeability and shear strength of unsaturated soils. While flooding is a concern during this time period, designers should pay more attention to the understanding of the saturated situation. Shear strength, volume change, and compressibility parameters are used in geotechnical design. However, soil stiffness has been less considered, leading to a decrease in the lifespan of geotechnical infrastructure due to fatigue. This study is carried out in order to evaluate the influence of suction on soil stiffness at various strain levels during the wetting and drying cycles. The soil stabilisation method utilising Ordinary Portland Cement (OPC) is used to increase the strength of subgrade materials in order to meet the specifications for low-volume road materials. Based on the previous project (FRGS/1/2019/TK01/UTM/02/13) and using a modified oedometer with bender elements, a series of laboratory experiments will be performed using 6 per cent cement content dosages under unsaturated conditions. This study is expected to establish a relationship between the wetting and drying cycles that influence soil stiffness. This method of determining the soil stiffness of lateritic soil treated with OPC under cyclic soaking and drying is recommended as a subgrade material guideline for roads with low traffic volume.


Interested to join this work Please contact Muhammad Azril Hezmi- azril@utm.my

Fig. 1 Distribution of Residual Soil in Malaysia
Fig, 2 Cross section of Pavement and Railway tracks construction
Fig. 3 Stiffness measurement in construction
Fig. 4 Occurrence of unsaturated soil
Fig. 5 Initial Shear stiffness with suction

Role of SWCC in Practice

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Blight Lecture, – ISMCGE 2017 
Delwyn G. Fredlund, Senior Geotechnical Engineering Specialist, Golder Associates

Introduction

In Seoul 2017, Prof Fredlund one of top Unsaturated Researcher had delivered a talk in Soil Water Retention Curve in practice. The talk was delivered in Blight Lecture  in ISSMGE conference. Basically, Soil Water retention curve is the relationship between the water content, θ, and the soil water potential, ψ. This curve is characteristic for different types of soil, and is also called the soil moisture characteristic.

It is used to predict the soil water storage, water supply to the plants (field capacity) and soil aggregate stability. Due to the hysteretic effect of water filling and draining the pores, different wetting and drying curves may be distinguished.

The general features of a water retention curve can be seen in the figure, in which the volume water content, θ, is plotted against the matric potential, {\displaystyle \Psi _{m}}\Psi_m. At potentials close to zero, a soil is close to saturation, and water is held in the soil primarily by capillary forces. As θ decreases, binding of the water becomes stronger, and at small potentials (more negative, approaching wilting point) water is strongly bound in the smallest of pores, at contact points between grains and as films bound by adsorptive forces around particles.

Sandy soils will involve mainly capillary binding, and will therefore release most of the water at higher potentials, while clayey soils, with adhesive and osmotic binding, will release water at lower (more negative) potentials. At any given potential, peaty soils will usually display much higher moisture contents than clayey soils, which would be expected to hold more water than sandy soils. The water holding capacity of any soil is due to the porosity and the nature of the bonding in the soil.

 

 Please watch and read the full information below especially for Geotechnical Engineering Post Graduate Students.

Click Here_>>>>>Full paper Hons. Blight Lecture

Click Here >>>>>> Full video

Climate Change induced beach erosion

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Beach profile changes are subjected to various parameters such as tides, currents and wave effect. This study investigates the beach profile changes at Teluk Gorek Beach, Mersing and to evaluate the effect of soil density on beach sediment. A total of seven beach profile cross- sections with offset of 20 m apart were established to monitor the presence of erosion and accretion. The monitoring work was done on January and March 2016 during spring tide. The estimation of erosion and accretion were performed by comparing the profile obtained on January and March. The result shows that the beach profiles have experienced both erosion and accretion during the period of study. The soil density change varies to the erosion and accretion process. As a conclusion, the beach is slightly changes during the period of study. The density increase for erosion process while decrease when accretion takes place.

CLICK HERE FOR FURTHER DETAILS:—-> FULL PAPER

 

 

Gunung Pulai in the eyes of the world

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Campbell Scientific had published our work in Gunung Pulai in December 2016 newsletter. We have been using their equipment supplied by SureChem  (Malaysia). Rain gauge and water level transmitter have been used as part of our integrated  Early Warning Systems developed by Department of Geotechnics& Transportation, Faculty of Civil Engineering UTM.  We also managed to produce SOP for early warning system for gunung pulai mudflow. The SOP currently is undertaking several process of copyright before been published to the public.

 

The full details of the newsletter  as below:-

 

Click here for the article—  Campbell scientific newsletter 

Gunung Pulai Official Re-Opening

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KULAI: The Gunung Pulai Forest Reserve, which was closed down some 15 years ago following a tragedy that saw the loss of five lives, has finally reopened to the public with an early warning system installed for the safety of visitors.

Johor Education, Information, Entrepreneur and Cooperatives Development executive committee chairman Datuk Md Jais Sarday said the forest reserve was thoroughly inspected with safety measures in placed before its doors were reopened.

He added, however, only the lowest level of the area is accessible to the public while level two and level three were still being monitored.

“We have three officers from the Forestry Department on duty here daily to ensure visitors abide by the rules and regulations as well as to monitor the safety of the public,” he told reporters after launching the reopening ceremony here on Tuesday.

  The official reopening ceremony was also in conjunction with the International Forest Day 2016 state-level celebrations here.

In Dec 2001, the Gunung Pulai Forest Reserve was ordered shut following a landslide incident that took the lives of five and destroyed four homes at Kampung Sri Gunung Pulai here.

Source: www.thestar.com.my/news/nation/2016/09/06/gunung-pulai-forest-reserve-reopens-with-better-safety-measures/

Malay Version

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KULAI: Kerajaan negeri yakin pembukaan semula Hutan Lipur Gunung Pulai 1, dekat sini, selepas ditutup hampir 15 tahun sejak Disember 2001, mampu merancakkan kembali pertumbuhan ekonomi setempat. Pengerusi Jawatankuasa Pendidikan, Penerangan, Pembangunan Usahawan dan Koperasi Johor, Datuk Md Jais Sarday, berkata kawasan rekreasi itu yang dibangunkan semula dengan kos hampir RM700,000 bukan sahaja mampu menarik kehadiran lebih ramai pengunjung dari dalam dan luar negara, malah perlu dimanfaatkan oleh penduduk kampung. “Selain menempatkan Pejabat Penguat Kuasa Jabatan Perhutanan Johor, kemudahan lain yang dibina untuk keselesaan pengunjung ialah pondok rehat dan tandas serta dilengkapi sistem amaran awal. “Dengan beroperasi semula hutan lipur ini, kita percaya ia akan kembali menjadi tarikan ramai dan peluang ini seharusnya digunakan penduduk setempat untuk menambah pendapatan masing-masing. Misalnya mereka boleh membuka restoran, kedai menjual cenderamata atau menjadi pemandu pelancong. “Pada masa sama, kerajaan negeri amat berharap pengunjung akan sentiasa menjaga kemudahan yang disediakan dan tidak membuang sampah merata-rata,” katanya. Beliau yang mewakili Menteri Besar, Datuk Seri Mohamed Khaled Nordin berkata demikian pada sidang media selepas merasmikan Pembukaan Semula Hutan Lipur Gunung Pulai 1 sempena sambutan Hari Hutan Antarabangsa Peringkat Negeri Johor di sini, hari ini. Hutan lipur itu ditutup pada 26 Disember 2011 atas arahan Majlis Keselamatan Negara (MKN) berikutan tragedi banjir lumpur di kawasan rekreasi berkenaan sehingga mengorbankan lima orang, selain empat rumah turut musnah dihanyutkan air deras di Kampung Sri Gunung Pulai, dekat sini.

Selanjutnya di : http://www.bharian.com.my/node/190264

 

 

Consultation: Underprivillage Community Water Supply

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After a few visit to site and geophysic testing on the Site on last Jun 2016. The consultation and research team members have decided to choose Vertical Tube Well as to increase the quality and quantity of Orang Asli Kg. Air Pasir Kluang water supply. Although there is existing vertical tube well, however the quantity of the water a bit short to fullfill the needs. Based on the Geophysical investigation using Resistivity testing. The team had concluded a new location of vertical tube well intake should be installed.

Consultation: Installation of Early Warning System for mud flow landslides at Gunung Pulai

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Alhamdulillah the Early Warning System has been installed. Currently two stations consist of rain gauge and water level to record and collect the data. Both station controlled by a control box that monitor the rainfall and water level increment. If the any of the parameter been triggered which may lead to mud flow the warning light and siren will be activated to the public.

Consultation & Community Service : Water Supply for Underprivilage Community

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Alhamdulillah I was appointed by Dr. Ali ( Team Leader) for Water Supply project for Under Priviliage Community  as Geotechnical Laboratory  Team members. The project focused in providing sufficient water supply in remote area in Kahang, Kluang for 15 families of Orang Asli. The team had second site visit on the verification of existing water supply on site. Two options had been identified as solutions for the problem. Both methods will use Ground Water as source of water supply. The methods will be either Vertical Tube Well or Horizontal Well which include River Bank Filteration will be chosen as solution to the water supply.

The team member consists of
1. Dr. Ali
2. Dr. Norhan
3. Prof Maketab

4. Prof Nordin
5. Dr. Faizal

Unanswered questions in unsaturated soil mechanics- SHENG DaiChao, ZHANG Sheng & YU ZhiWu

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ABSTRACT

The last two to three decades have seen significant advances in the mechanics of unsaturated soils. It is now widely recognized that the fundamental principles in soil mechanics must cover both saturated and unsaturated soils. Nevertheless, there is still a great deal of uncertainties in the geotechnical community about how soil mechanics principles well-established for saturated soils can be extended to unsaturated soils. There is even wide skepticism about the necessity of such extension in engineering practice. This paper discusses some common pitfalls related to the fundamental principles that govern the volume change, shear strength and hydromechanical behaviour of unsaturated soils. It also attempts to address the issue of engineering relevance of unsaturated soil mechanics.

KEY QUESTIONS?

In particular, some basic questions are often raised on the fundamental principles that govern the hydromechanical behaviour of unsaturated soils and on the engineering relevance:

(1) Reconstituted soil versus compacted soil. What are the main differences in the hydromechanical behaviour of these soils? What are the implications of different pore size distributions (PSD), in constitutive modelling of unsaturated soils? Can a reconstituted soil become collapsible?

(2) Relationship between volume change, yield stress and shear strength. Can the constitutive equations for volume change, yield stress and shear strength be defined separately? Does the loading-collapse yield surface have to recover the apparent tensile strength surface? Do we need the suction-increase surface to capture possible plastic volume change when a soil is dried to a historically high suction? What are the implications of stress state variables in defining volume change and shear strength equations?

(3) Implications of using a Bishop effective stress. Can we use a Bishop-type effective stress in modelling unsaturated soil behaviour and what are the implications?

(4) Engineering relevance. What is the relevance of the unsaturated soil mechanics in engineering practice? Is a design based on the saturated soil mechanics always conservative? Considering the difficulty and uncertainty in measuring or monitoring in-situ suctions, the applicability of the unsaturated soil mechanics to engineering practice has also been questioned. These questions represent some of the most fundamental issues in unsaturated soil mechanics. There are currently no unified answers to these questions.

Continue reading →

Unsaturated soil zone

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The unsaturated zone is the part of the subsurface between the land surface and the groundwater table. The definition of an unsaturated zone is that the water content is below saturation (for the specific soil). Hence, ‘unsaturated’ means that the pore spaces between the soil grain particles or the pore space in cracks and fissures are partially filled with water, partially with air. The unsaturated zone can be from meters to hundred of meters deep.

If an unsaturated zone exists below the ground surface the water infiltrating through the top soil will flow vertically through the unsaturated zone before the water recharges the saturated zone. From the unsaturated zone, the water is lost by i) plant uptake (transpiration), ii) direct soil evaporation and iii) recharge. In the unsaturated zone, the driving force for the flow of water is the vertical gradient of the hydraulic head (consisting of gravity and capillary forces), and the soil characteristics (unsaturated hydraulic conductivity).

The vertical flow through an unsaturated soil is solved numerically using the Richards Equation. This equation is developed by combining the Darcy’s law with the law of conservation of mass and the result is a partial differential equation for one-dimensional vertical flow in unsaturated soil.

 

Source: http://iwmi.dhigroup.com/hydrological_cycle/unsaturatedflow.html