Suched Likitlersuang

Investigation on the effects of gradation and aggregate type to moisture damage of warm mix asphalt modified with Sasobit

Moisture damage is one of the major concerns for warm-mix asphalt (WMA) because it is hypothesised that the reduction in mixing temperature could adversely affect the moisture sensitivity of WMA. The aggregate type and their properties are also one important factor affecting the moisture damage of WMA. This study focused on understanding the effect of aggregate structure and its physical properties on the mechanism of moisture damage in WMA. This study evaluated the moisture sensitivity of hot-mix asphalt (HMA) and WMA as reflected in the permanent deformation. The effects of aggregate gradation and aggregate types on the moisture damage were also evaluated. The results from this study show that WMA is more resistant to permanent deformation than HMA as indicated by lower permanent strain rate and higher flow number (FN). Gradation has an effect on the permanent deformation in granite and slag mixes due to the difference in aggregate properties. WMA is more sensitive to moisture damage than HMA as shown in lower ratios of FN and permanent deformation rate. Fine-graded mixtures appear to have greater resistance to moisture damage than coarse-graded mixtures for both HMA and WMA. The result could be due to the different structure of air void distribution in the mixes of different gradation. It was found that the proper selection of aggregate type and aggregate structure could reduce the moisture damage problem of WMA.

An investigation of anisotropic elastic parameters of Bangkok Clay from vertical and horizontal cut specimens

This paper presents an investigation of cross-anisotropic elastic parameters of Bangkok Clay. The study programme consists of both laboratory experiments and parametric analysis. A set of isotropically consolidated undrained and drained triaxial compression tests is performed on vertically- and horizontally-cut undisturbed specimens. The triaxial apparatus is equipped with local strain measuring systems and bender element which enable the measurement of stiffness at small to intermediate strains. The anisotropic stiffness parameters obtained from both undrained and drained triaxial tests are assumed to follow the three-parameter cross-anisotropic elastic model proposed by Graham and Houlsby (1983). Moreover, the elastic moduli are also assumed as power functions of isotropic confining stress. The cross-anisotropic elastic parameters are then derived as functions of these relevant simplified parameters. The least-square method is used to define the optimised elastic parameters from all tests. Finally, a complete set of cross-anisotropic elastic parameters of Bangkok Clay is proposed and discussed against reported values from other soils.

Predictions of a continuous hyperplasticity model for Bangkok clay

The performance of a new constitutive model called ‘kinematic hardening modified Cam clay’ (KHMCC) is presented. The model is described using the ‘continuous hyperplasticity’ framework. Essentially this involves an infinite number of yield surfaces, thus allowing a smooth transition between elasticity and plasticity. The framework allows soil models to be developed in a relatively succinct mathematical form, since the entire constitutive behaviour can be determined through the specification of two scalar potentials. An implementation of the continuous hyperplasticity model is also described. The model requires eight parameters plus a viscosity coefficient for rate-dependent analysis. The model is defined in terms of triaxial stress–strain variables for this study, and is used to model monotonic triaxial tests on Bangkok clay. Comparisons of the theoretical predictions with the results of cyclic undrained triaxial compression tests on Bangkok clay are also presented.

On the numerical implementation of hyperplasticity non-linear kinematic hardening modified cam clay model

A continuous hyperplasticity model named kinematic hardening modified cam clay (KHMCC) is a constitutive soil model based on thermodynamic principles. This model has addressed some shortcomings of the modified cam clay (MCC), specifically on small strain stiffness. Because of employing multiple surfaces plasticity, it can simulate a smooth transition from elastic to plastic behaviour as well as the effect of immediate past stress. This article aims to present some important issues on the numerical implementation of the continuous hyperplasticity non-linear KHMCC model. The incremental stress–strain response is calculated based on a rate-dependent algorithm. A significant advantage of the rate-dependent calculation is that it is not necessary to attach with the consistency condition during calculation of plastic strains. Effect of time step and number of yield surfaces in rate-dependent algorithm will be also presented. A discussion on using of numerical integration rules of hardening functions is addressed. Furthermore, model verification is performed against analytical solution of ideal undrained response which has been obtained from theoretical integration of the MCC function over the imposed stress or strain path. Finally, some numerical demonstrations are also carried out to illustrate several key features of the model.

Influence of the spatial variability of shear strength parameters on rainfall induced landslides: a case study of sandstone slope in Japan

Rainfall-induced landslides frequently occur in humid temperate regions worldwide. Research activity in understanding the mechanism of rainfall-induced landslides has recently focused on the probability of slope failure involving non-homogeneous soil profiles. This paper presents probabilistic analyses to assess the stability of unsaturated soil slope under rainfall. The influence of the spatial variability of shear strength parameters on the probability of rainfall-induced slope failure is conducted by means of a series of seepage and stability analyses of an infinite slope based on random fields. A case study of shallow failure located on sandstone slopes in Japan is used to verify the analysis framework. The results confirm that a probabilistic analysis can be efficiently used to qualify various locations of failure surface caused by spatial variability of soil shear strength for a shallow infinite slope failure due to rainfall.

Temperature shift function of asphaltic concrete for pavement design in tropical countries

Pavement design in many tropical countries like Thailand refers to the standard of America or Europe. These quoted standards were produced from experimental database of cold climate zone which is totally different from database collected in tropical area. To directly employ the design standard from one place to another may not be always appropriate. One way is to transform the database to check for important factors such as temperature, where cold climate countries environment is significantly differently from those in the tropical zone. The objective of this article is to evaluate the behaviour of asphaltic concrete under the varying temperature and strain rate by using the principle of time–temperature superposition both in compressive and tensile modes. A series of unconfined compression and indirect tensile tests were performed to failure or at large strain level. For both test series, the temperature was varied from 10 to 55°C and four different loading rates were applied. The constitutive results of two tests were cross-plotted to produce the master curve and temperature shift function.

Stability Analysis of Vegetated Residual Soil Slope under Rainfall Conditions

Effects of climate change including intense rainfalls have resulted in many slope failures. The bioengineering method using vegetation is an environmentally-friendly alternative for slope stabilisation. This paper presents the effect of root reinforcement on stability of vegetated slope under rainfall condition. A transient seepage and slope stability analysis was conducted based on the finite element and limit equilibrium methods. A field monitoring on a residual soil slope in Thailand was numerically modelled. In transient seepage analysis, the soil water characteristic curve and the saturated permeability measured from laboratory and in-situ tests were used and the results are comparable with the monitored values from the site. For slope stability analysis, the effective shear strength parameters from direct shear tests were used to model the well-compacted and non-compacted soil slopes. The additional shear strength of soil from the root cohesion was modelled for vegetated soil slope. Results exhibit ...

Local Site Investigation of Liquefied Soils Caused by Earthquake in Northern Thailand

ABSTRACT Ambient noise measurements and spectral analysis of surface waves were performed in Mae Lao to investigate the local site effects of the May 5, 2014 Mae Lao earthquake in Northern Thailand. Site investigations were conducted to determine horizontal to vertical spectral ratio, predominant frequency, and shear wave velocity profile. The results showed that the liquefied locations were classified as Site Class D. The low Vs profile at the shallow depth confirmed evidences of liquefaction in this area. The results could bring an understanding of site response and dynamic behavior of soils during earthquake in the Northern Thailand.

Effects of water table fluctuation on diesel fuel migration in one-dimensional laboratory study

The effects of water table fluctuation on diesel fuel redistribution in unsaturated soil are investigated in the laboratory by one-dimensional column test. The simplified image analysis method is used to assess the saturation distributions of water and diesel in the flow domain under transient condition. The experiments are undertaken on two homogeneous sands to study the effects of different particle sizes. The two-phase experimental data illustrate soil–liquid characteristic curves (SLCCs) of water/air and diesel/air systems. The SLCCs of diesel/water systems can be predicted by scaling procedure. A descending order of matric suction at a given saturation of wetting phase is in the order of air/water, diesel/water and air/diesel systems. Coarser particle size gives smaller entry pressure, residual matric suction and residual degree of saturation. The three-phase (air/water/diesel) experimental data illustrate that, during imbibition stages, air and diesel are entrapped below water table with the entrapped air saturations of 18–24% and entrapped diesel saturations of 6–10% for fine sand. Coarser particle size yields smaller entrapped diesel saturations and larger entrapped air saturations. The residual diesel saturations during drainage stages and entrapped diesel saturations during imbibition stages do not show any systematic difference as these stages are repeated. During imbibition stages, 37–47% of the total amount of diesel fuel is entrapped under the water table. Also, there is no systematic difference in the amount of diesel fuel entrapped under the water table when imbibition stages are repeated.

Stability analysis of vegetated residual soil slope in Thailand under rainfall conditions

Effects of climate change including intense rainfalls have resulted in many slope failures. The bioengineering method using vegetation is an environmentally-friendly alternative for slope stabilisation. This paper presents the effect of root reinforcement on stability of vegetated slope under rainfall condition. A transient seepage and slope stability analysis was conducted based on the finite element and limit equilibrium methods. A field monitoring on a residual soil slope in Thailand was numerically modelled. In transient seepage analysis, the soil water characteristic curve and the saturated permeability measured from laboratory and in-situ tests were used and the results are comparable with the monitored values from the site. For slope stability analysis, the effective shear strength parameters from direct shear tests were used to model the well-compacted and non-compacted soil slopes. The additional shear strength of soil from the root cohesion was modelled for vegetated soil slope. Results exhibit ...