Natural Moisture Content Research Articles

Determination of the Pile Load Capacity of Collapsible Soils

Given the complexity of the tests and the ambiguity of the experimental and calculated estimates of the pile load capacity of collapsible soils, a method for determining it is proposed on the basis of the results of tests of soils with natural moisture content without insulation of piles within the collapsible thickness. The method decreases the cost and time of testing and increases the accuracy of the results.

Sensitivity of Permafrost Adjacent to Bored Pile in Wetland Tundra During Concrete Hydration Heating

The permafrost in wetland area is very sensitive to temperature change due to its special geological conditions. By observing the temperature data of the pile-soil junction of the bored concrete pile, as well as measuring the geotechnical parameters and thermophysical parameters of the soil around the pile, it statistically analyzes the significant correlation factors related to the time when the temperature of the pile-soil junction rises to the peak, including the dry density and liquid index of the frozen soil. The formula for calculating peak time is summarized and the fitting effect is compared. The results show that peak time is positively correlated with dry density and obeys cubic curve. It is negatively correlated with the liquid index and follows the growth function curve. The peak time was not significantly correlated with the buried depth of the temperature sensor, peak temperature corresponding to the peak time, natural ground temperature, original temperature of pile wall, soil thermal conductivity, volume heat capacity, natural moisture content and plasticity index of frozen soil. The influence of concrete ratio on peak time is significant, and its correction coefficient follows S-shaped curve.

Geotechnical Properties of Gopalganj Sub-soil in Bangladesh

Gopalganj town is situated on southern region of Bangladesh which is near to the coastal region. The sub-soil in this region is formed by the alluvial deposits from different rivers. For economical and effective selection and design of foundation, it is very important for geotechnical engineers to go for detailed investigations of geotechnical properties of sub-soil. Some soil samples were collected from Gopalganj town area and tested in the Geotechnical laboratory of Khulna University of Engineering and Technology (KUET), Khulna to determine the geotechnical properties of soil and other data were collected from soil investigation reports prepared by CRTS (Civil), KUET, Khulna. The sub-soil is composed of fine grained soils of soft to medium stiff consistency up to 30 ft depth from the existing ground surface and the soil predominantly consists of course grained soils of medium to very dense compactness below 30 ft depth. For the Gopalganj sub-soil the values of unit weight, specific gravity, natural moisture content, liquid limit, plastic limit, unconfined compressive strength, cohesion, angle of internal friction, compression index and natural void ratio varies from 13.23 kN/m³ to 14.21 kN/m³, 2.68 to 2.73, 32% to 65%, 33% to 60%, 26% to 48%, 5kPa to 90kPa, 0.93kPa to 8.20kPa, 27° to 38°, 0.16 to 1.0 and 0.83 to 2.30 respectively. For the construction of low rise building, shallow foundation may be used with or without replacing the soil layer below the foundation with sand having proper compaction. For medium to high rise buildings, pile or piled raft foundations may be used that penetrate through the soils of very soft to stiff consistency to deeper strata of dense compactness located at 30 to 40ft depth from the ground surface. The results obtained in this study will be useful for those owners who are interested to construct building without soil investigation.

Laboratory and Field Experimental Study on the Vacuum Preloading Method with Pumping and Discharging

Negative vacuum pressure hardly reaches deep soils due to the drain board bending and serious blockage with the existing vacuum preloading methods (VPMs), thus resulting in poor reinforcement relative to practical engineering applications. To address this issue, this paper proposes a vacuum preloading method with pumping and discharging (a new dredger filling foundation processing technique based on vacuum preloading). This new VPM is developed through technological improvement and plastic drain board innovations in traditional VPMs. The new VPM uses a plastic vertical drainage board with double drainage channels, and the core board is in a “tic‐tac‐toe” shape with a hollow centre and square pipeline channels. It can execute air and water drainage. Vacuum transfer holes were set at two grooves, every 2‐3 m from the central pipeline of the core board. Grooves at two sides of the core board and filter membrane were rolled together to improve drainage. In addition, the vacuum pipe, tube connector, and core board centre of the vertical plastic drainage board were connected directly and securely. A stereoscopic vacuum transmission system composed of a horizontal and vertical drainage system was built. In this vacuum transmission system, the transfer route was shortened, and the loss of vacuum along the route was decreased. The negative vacuum pressure was transferred to different soil depths through the central pipeline of the core board to accelerate the dissipation of pore pressure in soil mass and prevent vacuum pressure loss caused by drainage board bending, thus improving the reinforcement effect. Dredger filling silt foundation reinforcement by VPM and VPM with pumping and drainage were compared in laboratory simulations and field tests with different drainage boards. Test results show that the loss of vacuum pressure along the drainage path was relatively smaller in the new physical vapor deposition (PVD), and the pressure transfer efficiency was increased. Deep soil mass was reinforced effectively by using the new PVD. After reinforcement, the physical and mechanical properties of soil layers were improved. Moreover, soil strengths were remarkably improved, with sharp reductions in natural moisture content and porosity. Then, the transfer law of vacuum on different drainage boards and the reinforcement mechanism of VPM with pumping and drainage were analysed. Research conclusions show the superiority of VPM with pumping and drainage in terms of effectiveness and soft foundation reinforcement. This study provides a theoretical basis for the application and development of the new VPM.

Chapter 6 Collapsible Soils in the UK

Abstract Metastable soils may collapse because of the nature of their fabric. Generally speaking, these soils have porous textures, high void ratios and low densities. They have high apparent strengths at their natural moisture content, but large reductions of void ratio take place upon wetting and, particularly, when they are loaded because bonds between grains break down upon saturation. Worldwide, there is a range of natural soils that are metastable and can collapse, including loess, residual soils derived from the weathering of acid igneous rocks and from volcanic ashes and lavas, rapidly deposited and then desiccated debris flow materials such as some alluvial fans; for example, in semi-arid basins, colluvium from some semi-arid areas and cemented, high salt content soils such as some sabkhas. In addition, some artificial non-engineered fills can also collapse. In the UK, the main type of collapsible soil is loess, though collapsible non-engineered fills also exist. Loess in the UK can be identified from geological maps, but care is needed because it is usually mapped as ‘brickearth’. This is an inappropriate term and it is suggested here that it should be replaced, where the soils consist of loess, by the term ‘loessic brickearth’. Loessic brickearth in the UK is found mainly in the south east, south and south west of England, where thicknesses greater than 1 m are found. Elsewhere, thicknesses are usually less than 1 m and, consequently, of limited engineering significance. There are four steps in dealing with the potential risks to engineering posed by collapsible soils: (1) identification of the presence of a potentially collapsible soil using geological and geomorphological information; (2) classification of the degree of collapsibility, including the use of indirect correlations; (3) quantification of the degree of collapsibility using laboratory and/or in situ testing; (4) improvement of the collapsible soil using a number of engineering options.

Влияние естественной влажности на характерное время десорбции метана из углей различной степени метаморфизма

Goal. To study the effect of natural internal moisture content on the kinetics of methane desorption from coals of varying degrees of metamorphization. Methodology. For the research, coal was used after a long (more than 100 days) preliminary exposure in a dry, closed indoors. The measurements were carried out on several samples of Donbass coals with different volatile content. Two groups of coal samples were used - dry, with natural internal humidity and one sample with artificial humidity of 1.5%. The volumetric method was used for measurements. The method includes three stages: 1st  saturation of coal with compressed methane, 2nd  preliminary discharge of compressed gas from a container with coal after its saturation, and 3rd  collection of methane released by coal into a storage vessel. Before registration of desorption, pressurized gas was discharged from the free volume of containers into the atmosphere. The desorption unit contains a low-temperature trap (78°C) for water vapor and a warming radiator for methane entering the storage vessel. To determine the numerical values of the characteristic time of desorption of methane from coal, we used information on the change in gas pressure in the storage vessel during desorption. To analyze the results, a method based on the concept of a change in the characteristic relaxation time of desorption during methane emission was used. Results. Experimental results show that in wet coals the ratio between the amount of methane in coal and the intensity of its outflow at any desorption site is less than in dry coals. It was found that in coals of the metamorphic series the presence of natural moisture leads to a decrease in the intensity of methane emission, a decrease in the characteristic desorption time and a decrease in the activation energy of methane desorption by 0.4 - 2.5 kJ / mol. The features of the kinetics of desorption indicates competition energetics of interactions between methane and water with the surface of the pores of coal. Scientific novelty. It was found that even without artificial humidification, but in the presence of natural internal moisture in coal, the degassing time during desorption is reduced (in comparison with dry coal). Practical significance. The research results can be used to optimize the duration of hydraulic saturation of the coal seam and the water consumption during coal degassing.

Assessment of Soil Thermal Conductivity Based on BPNN Optimized by Genetic Algorithm

Thermal conductivity is a critical parameter playing an important role in the heat transfer process in thermal engineering and enormous other engineering fields. Thus, the accurate acquisition of thermal conductivity has significant meaning for thermal engineering. However, compared to density test, moisture content test, and other physical property tests, the thermal conductivity is hard and expensive to acquire. Apparently, it has great meaning to accurately predict conductivity around a site through easily accessible parameters. In this paper, 40 samples are taken from 37 experimental points in Changchun, China, and the BPNN optimized by genetic algorithm (GA‐BPNN) is used to evaluate the thermal conductivity by moisture content, porosity, and natural density of undisturbed soil. The result is compared by two widely used empirical methods and BPNN method and shows that the GA‐BPNN has better prediction ability for soil thermal conductivity. The impact weight is obtained through mean impact value (MIV), where the natural density, moisture content, and porosity are 30.98%, 55.57%, and 13.45%, respectively. Due to high complexity of different parameter on thermal conductivity, some remolded soil specimens are taken to study the influence of individual factors on thermal conductivity. The correlations between moisture content and porosity with thermal conductivity are studied through control variable method. The result demonstrates that the impact weight of moisture content and porosity can be explained by remolded soil experiment to some extent.

Stability Prediction in Earthfill Dams with Regard to Spatial Variability of Strength Properties of Loamy Soil

Based on the analysis, generalization and statistical processing of experimental data, the guideline values are determined for the physical and mechanical properties of loamy soil for construction of earthfill dams at liquid mining waste storages. A close parabolic relationship is found between the cohesion, internal friction angle and natural moisture content of soil. The authors present the method of real-time prediction of earthfill dam parameters with regard to spatial variability of soil strength.

Інженерно-геологічна характеристика порід лесово-ґрунтової серії опорного розрізу Лисогора (Подільська височина)

The Lysohora key section is one of the most complete and interesting sections of the loess-palaeosol sequence of the eastern part of Podolian Upland. This is the area where the Pleistocene loess-palaeosol sequence was deposited directly on the rocks of Precambrian crystalline shield, its weathered part (eluvium). The value of engineering-geological research of the section is increasing due to the fact that it is located near the city of Vinnytsia, which has been intensively built up in recent years. We emphasize that in this section Upper Pleistocene loesses play a minor role. The value of the Middle Pleistocene loesses, which are generally poorly studied, is abruptly growing. The Lysohora section was sampled. Above 30 monoliths were taken with the purpose of studying the engineering-geological characteristics of the sediments. Among them are grain size distribution, natural moisture content, plasticity index, soil density, porosity coefficient, subsidence, angle of internal friction, specific cohesion, deformation modulus, chemical composition of aqueous extract, humus content, CaCO3 content, etc. The results of the exploration of the loess-palaeosol sequence properties are correlated with the corresponding stratigraphic horizons of the other sections of Podolian Upland. Besides the main section, which was described in a pit, two additional cuts were studied: one on the Korshiv palaeosol complex, another one on the ice wedge pseudomorphosis of Yarmolyntsi palaeocryogenic stage. It is revealed that loess and palaeosol horizons are very different in their engineering-geological properties. In particular, insignificant subsidence is a characteristic of only individual samples from the upper horizon of the Middle Pleistocene loesses. Palaeosol horizons usually have higher values of density and natural humidity. They have a heavier particle size distribution. According to the analysis of the water extract, the highly soluble salts are practically washed away from the loess-palaeosol series. The significant influence of palaeocryogenesis processes on the formation of engineering-geological properties of rocks is also described. Key words: loess-palaeosol sequence, Pleistocene, engineering-geological characteristic of sediments, palaeocryogenesis.

Suitability of Olokoro and Amaoba lateritic soil as pavement construction materials

The suitability of Olokoro and Amaoba lateritic soils as pavement construction materials was investigated. Soil samples were collected from the borrow sites and were subjected to preliminary tests (natural moisture content, specific gravity, particle size analysis and Atterberg limits) and strength tests (compaction and California Bearing ratio, CBR). The liquid limit, plastic limit and plasticity index were found to be A-2-7 soil according to AASHTO classification for Olokoro and A2-6 AASHTO classification for Amaoba sample. The Olokoro sample has average value of the dry density as 1.87g/cm3 and average optimum moisture content of 15.6%. Whereas Amaoba has average maximum dry density of 1.88g/cm3 and average optimum moisture content of 16.1%. Both soils were found to have the same average specific gravity of 2.6 having liquid limit of 44% and 40% for Olokoro and Amaoba with plastic limit of 30% and 18%, plasticity index of 14% and 22% respectively. Based on the CBR values 20.3% and 19.67% respectively obtained from the two samples, the two lateritic soil will require modifications to help improve their properties for use as sub base and base materials. However, both of the soil samples are good fill materials in road work constructions.Keywords: Laterite, pavement, compaction, optimum moisture content, materials

Utilization of Palm Fruit Fibers as Constituent Materials for Hand Mould Clay Bricks

The production process of palm oil generates a huge amount of waste. As Nigeria is one of the largest producing countries, the fruit fiber wastes from palm oil processing have received a low level of waste management and have been a long-term environmental concern. This study is focused on recovery of the palm fruit fibers and its utilization as a constituent material for locally hand mold clay bricks. Varying percentages (1% to 3%) of palm fruit fiber was introduced into local hand mold clay. The bricks produced were tested for optimum moisture content and dry density. Some preliminary tests such as natural moisture content determination (wet and dry), Specific gravity test, Particle size distribution test (Sieve analysis), Atterberg limit test, Compaction test (Standard Proctor), Water absorption test, and Compressive strength test was carried out. The results show a decrease in optimum moisture content as the percentage of the palm fruit fibers increased from 1% to 3% in the soil sample while the maximum dry density increased. With the addition of 1% to 3% of the palm fruit fibers and the mix sun-dried, noticeable improvement in the compaction characteristics of the soil sample was observed. It can be deduced from the results that for a good construction clay soil, the lower the moisture content, the higher the dry density and the better the quality of bricks. Production of clay bricks with palm fruit fibers could serve as an economic substitute for the growing cost of sandcrete blocks.

A note on sample drying method and natural moisture content of tropical red soils from the Republic of the Congo

This technical note describes the effects of drying method on the reported moisture content of tropical red soils from a case study site in the Republic of the Congo, Africa. Tropical soils are often considered to exhibit unique geotechnical characteristics which are often ascribed to the chemical compositions and micro-structures of a pedogenic material developed under hot, wet, soil-forming conditions. The applicability of conventional soil index tests for the identification and classification of such soils has therefore been questioned, primarily because of the dependence of such tests on the sample preparation process and the changes to the natural soil conditions which may occur during sampling and preparation. This holds true for determination of moisture content which, expressed as a proportion of the mass of the dry solid particles, can vary markedly, depending on the precise drying procedure undertaken. It is frequently suggested throughout the literature that air-drying methods, as opposed to conventional oven-drying, should be used to determine moisture content values for these soils. The findings of this study however suggest that, whilst such drying methods may be appropriate for certain tropical soils, a variation in the reported natural moisture content results may occur depending on the drying method used.

Groundwater Quality Assessment near an Open Dump Municipal Solid Waste Disposal Site in Ekiti State, Southwestern Nigeria

This study assessed groundwater quality around an open dump municipal solid waste (MSW) disposal site at Ilokun, a village on the outskirts of Ado-Ekiti, Ekiti State, Nigeria. Three geotechnical boreholes and three water boreholes (tube wells) were drilled at intervals of 15m, 30m and 45m away from the disposal site. Soil samples were obtained near the top and at the bottom of the geotechnical boreholes. Tests carried out on these samples included the sieve analysis, specific gravity, bulk density, natural moisture contents, Atterberg limits, linear shrinkage, and hydraulic conductivity tests, and these were used to index and classify the soils at the landfill dumpsite. It was discovered that the soils belonged to the clay and clayey-sand USCS groups (CL and SC mainly). Groundwater samples were taken from the three water boreholes (tube wells), and physical, chemical and microbiological investigations carried out on the water samples and on water obtained from an existing hand-dug well in the neighbourhood of the dumpsite. The parameters obtained from the tests on the samples were compared with the Guidelines for Drinking Water Quality of the World Health Organisation (WHO) and the Nigerian Standard for Drinking Water Quality of the Standards Organisation of Nigeria. The water quality parameters determined included: the acidity (pH), temperature, electrical conductivity (EC), colour and odour, turbidity, dissolved oxygen (DO), biochemical oxygen demand (BOD), total dissolved solids (TDS), total hardness (TH), and contents of the constituents such as total iron, chloride, sulphate, nitrate, etc. The microbiological characteristics determined are the Total Bacterial Count (Total coliform count), and the presence of Faecal streptococci, Staphylococcus aeurus and Escherichia coli. It was discovered that the groundwater at the dumpsite has been heavily contaminated and unfit for human consumption or usage without appropriate treatment to render them potable and fit for domestic use.

Study on the dynamic characteristics of solidified silt under dynamic load

The treatment and utilization of silt have always been a difficult problem in the field of engineering construction. Because of its high natural moisture content, low permeability and strength, rheological property and rich organic matter, the silt soil cannot be directly used in engineering practice. Under this background, in order to further explore the dynamic characteristics of solidified silt under dynamic load, a shallow mud along the coast of the Pearl River Delta in Guangdong Province was used as raw material, inorganic liquid solidifying agent and 32.5 ordinary Portland cement as solidifying agent. The dynamic characteristics of silt and solidified silt with age of 7 days and 28 days were studied by means of dynamic triaxial tests. The loaded samples were analyzed by SEM in laboratory. The experimental results show that the dynamic characteristics of the solidified silt soil under dynamic load are much better than that of the remoulded soil, and the solidification effect of the solidified silt soil with an age of 28 days is more obvious. The results can be applied to practical engineering practice.

Determination of the Geotechnical Parameters of Soils Behavior for Safe Future Urban Development, Najran Area, Saudi Arabia: Implications for Settlements Mitigation

This paper deals with the geotechnical characterization of Sultana soils (Najran region, Saudi Arabia) by in situ and laboratory tests, for a project proposal for the construction of commercial and government buildings. Geotechnical parameters of the subsoil were analyzed with a view to using the soil as an earth construction material and as a foundation for buildings constructed on the grounds tested. The site was investigated by means of boreholes, trial pits, standard penetration tests, plate load tests, Seismological data, particle size analyses, modified Proctor Tests, Oedometer and direct shear tests. The study contains full description to the subsurface soil conditions and provides recommendations for collapse potential, foundation type, foundation depth, allowable net bearing capacity, estimation for the expected settlement. In this paper a review of the principal results of the in situ and laboratory investigations is described. Results of the study revealed that within the maximum depth of 10.0 m of boring, the soil was found to be composed of brown soil mixture of sand and clayey silt with little gravel, classified as (SM) and (SC) according to USCS classification and as (A-2-4) and A-2-6 according to AASHTO classification. The area was found to consist in general of collapsible soils, classified as collapsible alluvial soils. The results show that the collapse potential of the majority of semi-arid soils tested were classified as severe trouble soils and natural moisture content is an important factor influencing the collapse potential of the soil. In addition, the results of this study provide the parameters to evaluate the soil behavior and the geotechnical model for the foundation bearing capacity and soil settlements evaluation.

Geotechnical Evaluation of Road Pavement Failure along the Awotan-Akufo Road, Oyo State Southwestern Nigeria

In order to access the cause(s) of road failure and proffer preventive measures for the future reconstruction of the Awotan-Akufo road, southwestern Nigeria, the geotechnical engineering properties of the subgrade soil, asphalt pavement thicknesses, drainage and traffic load were evaluated. Soil samples were collected from test pits 1 m deep and at an interval of 50 m and subjected to geotechnical analyses in accordance to AASTHO specification. The grain size distribution revealed that 70% of the entire samples from Awotan-Lifeforte and Adaba failed sections along Akufo road contain amount of fines more than 35% passing through sieve No. 200. The Natural Moisture Content range from 5.73 - 20.21% (Awotan-Lifeforte section) and the entire samples from Adaba failed sections have high natural moisture content ranging from 16.20 - 23.20%. From Atterberg limit test, the Liquid limit of 12 - 56% (Awotan-Lifeforte section) and 26.00 - 40.00% (Adaba Section) were obtained. The Plastic Limit and Plasticity Index of the soils ranges from 8.43 to 49.10% and 1.01 to 7.0% (Awotan-Lifeforte section), and 23.10 - 35.50% and 1.50 - 7.10% (Adaba Section) respectively. Linear shrinkage varies from 0.80 to 9.60% and from 3.10 to 8.80% for Awotan-Lifeforte and Adaba sections, respectively. The Maximum Dry Density of the soils ranged from 1.625 - 1.835 mg/m3 at Optimum Moisture Content of 13.4 - 17.3% (Lifeforte-Awotan section), and MDD of 1.752 - 1.975mg/m3 at Optimum Moisture Content of 13.4-17.3% (Adaba section). The unsoaked California Bearing Ratio are 30.08, 70.14, 39.08%, and the soaked California Bearing Ratio values are 26.17, 11.41, 33.41% (Lifeforte-Awotan section) respectively. At Adaba section of the road, the unsoaked California Bearing Ratio is 3.46, 87.70, 70.14%, and soaked California Bearing Ratio values are 3.42, 32.56, 39.83%. The average asphalt pavement thicknesses around Awotan-Lifeforte section range from 0.60 - 1.10 inches, and that of Adaba section range from 0.57 to 1.46 inches. The study concluded that the road pavement subgrade is silty clay and the geotechnical properties rated below the specifications of the Federal Ministry of Works and Housing at some failed portions. Asphalt pavement thicknesses are grossly inadequate and far below NAPA 2007 recommendation. As such the road cannot withstand the heavily loaded trucks that ply it on regular basis. All aforementioned contributed to the untimely failure of the road.

The Influence of Kaolinite - Illite toward mechanical properties of Claystone

Abstract This study investigates the relationship between clay minerals (kaolinite and illite) and rock properties of the claystone, including both mechanical (cohesion, friction angle, stress, and strain) and physical properties (natural water content, void ratio, and wet density), belonging to Warukin Formation of Kalimantan, Indonesia. Mineralogical characteristics of these rocks were studied using petrological and X-ray diffraction techniques, whereas the mechanical and physical properties were tested by conducting uniaxial and triaxial tests. Relationship among the variables was determined using correlation coefficients. It was observed that the mineralogy of the rocks pose strong constraints on their engineering properties. The results showed that an increase in illite content decreases cohesion, friction angle, strength, and safety factor; and increases natural moisture content, void ratio, and wet density. Although illite content of these rocks was just about 10.8% of the total minerals, it has significantly contributed to the modification of physical and mechanical properties. In contrast, kaolinite did not have a significant impact; since the correlation between various parameters was significantly low (correlation coefficient was much less, <0.3). Therefore while selecting the materials for geotechnical engineering applications, illite emerges as a safer alternative to kaolinite, especially when its concentration is less than 10.8% of the total rock mass.

Characteristic Research on Dynamic Strength of Remolded Unsaturated Loess Under Different Moisture Content

Luoyang remolded unsaturated loess samples under different natural moisture content were prepared, and then their dynamic strength was tested. The dynamic strength parameters of original loess were obtained when corresponding failure vibration frequency Nf was 10 and 20 times. According to dynamic strength parameters, the present research analyzed changing rules of dynamic strength parameters of remolded unsaturated loess with moisture content and failure vibration frequency. The paper further explores impact of natural moisture content and failure vibration frequency on unsaturated loess dynamic strength index in the region, and fits relationship curve between dynamic strength parameter of unsaturated remodeled loess and natural moisture content, thus propose mathematical expressions. It is shown from the results that there is an obvious linear relationship between dynamic internal friction angle and moisture content. When both dynamic cohesion and moisture content are logarithmized, they will present a good symbol linear relationship.

Effect of the root biotechnical characteristics of Alnus subcordata, Paulownia fortunei and Populus deltoides on the soil mechanics

The effect of root reinforcement depends on the biotechnical characteristics of the root system including the tensile strength of individual roots, the root density and the distribution of the root system in the soil. This research was conducted in the Hyrcanian forest in Iran, where shallow landslides are frequent due to road construction. The effect of the root biotechnical characteristics of Alnus subcordata, Paulownia fortunei and Populus deltoides each one in 2-, 10- and 15-year-old plantations was assessed. The profile trenching method was used in this study to obtain the root area ratio of individual species by counting the number of roots and measuring the root diameter. For each species, single root specimens were sampled and tested for tensile tests in the laboratory using the standard Instron apparatus. The natural moisture content (two weeks after rainfall), Atterberg limits, shear strength of the soil were determined for plantations, stable and unstable sites. Results of this study indicated that plastic index and internal friction angle decreased with increasing root diameter rate. Moreover, internal friction angle and cohesion increased with increasing root area ratio and root diameter and density index. Tensile strength of roots decreased with increasing stand age. The highest and the lowest tensile strengths among species were observed for Paulownia fortunei and Populus deltoides, respectively. The findings of this research contribute to expanding the knowledge of root biotechnical properties of some tree species and to the choice of the most appropriate species for improving plastic index and shear strength in landslide prone areas.

Selection of Physical and Chemical Properties of Natural Fibers for Predicting Soil Reinforcement

In this chapter, the physical and chemical properties of natural fibers (i.e., natural moisture content, specific gravity, breaking tensile strength, breaking strain, cellulose, hemicellulose, lignin and ash) were examined for their influences in the soil reinforcement. A total of 11 factors including soil moisture content, soil density and fiber percentage were evaluated by using the Bayesian nonparametric general regression (BNGR) method. The robustness of the BNGR algorithm was validated using k-fold cross-validation. A parametric study was carried out to unveil the effects of these input variables. The results indicated that a higher fiber percentage or larger soil density induces higher reinforcement effect. Besides, the cellulose in a natural fiber is found to have a significant effect on the unconfined compressive strength (UCS) followed by the ash. With respect to the physical properties, the breaking strain is found to be highly correlated with the UCS, while the effects of fiber natural moisture content, specific gravity and breaking tensile strength are less significant parameters.