Estimating shear strength parameters of a fine-grained alluvial soil using resedimented samples and multivariate regression

Two new improved-efficiency techniques for soil sampling by in situ freezing were used to obtain undisturbed samples of saturated alluvial volcanic soils, locally termed “Shirasu”, from Kagoshima city, Japan. Undrained cyclic triaxial tests were conducted on the undisturbed alluvial Shirasu samples obtained from a depth of 5.4 to 6.0 m at site A, and from a depth of 8.4 to 10.5 m at site B, after they had been thawed. For studying the effects of sample disturbance, undrained cyclic triaxial tests were also conducted on the reconstituted specimens. The liquefaction resistance in the field was estimated based on the laboratory tests. Based on the above studies it was shown that (1) two new developments in the technique of sampling by in situ freezing were successfully achieved in the field, and (2) compared with the liquefaction resistance of the undisturbed samples, that of the reconstituted samples from site A, all of which had about the same density, was about 45 to 50% of the value for undisturbed samples, and that of the reconstituted samples from site B, with relative density 13 to 20 percentage points higher than that of undisturbed samples was about 62 to 67%.

Effect of sample disturbance on soil water repellency determination in sandy soils

The dynamics of P in soil is greatly influenced by the adsorption of phosphate onto Fe‐oxides. Access of phosphate to the surface of these minerals depends on the degree of soil aggregation, which in turn is influenced by soil management system. The primary purpose of this work was to investigate P adsorption and desorption in undisturbed and disturbed soil samples from an Ultisol (Rhodic Paleudult) and an Oxisol (Humic Hapludox) under conventional tillage (CT) or no‐tillage (NT). Phosphorus adsorption and desorption in undisturbed soil was studied by using a continuous flux system containing a P solution for adsorption measurements or deionized water and Mehlich‐I solution for desorption measurements. The Oxisol, which had higher clay, hematite, and goethite contents than the Ultisol, exhibited the highest maximum P adsorption capacity (Pmax) values in disturbed samples. Also, the disturbed Ultisol samples had lower Pmax values under NT than under CT. The undisturbed soil samples exhibited no significant differences in P adsorption between soil management systems, but P desorption was more marked under NT than under CT. The samples of Oxisol under NT exhibited lower P adsorption rates and higher P desorption rates than the CT samples of the same soil. The decreased P adsorption in undisturbed samples relative to disturbed samples suggests that P adsorption is influenced by physical properties of soil.

Estimation of the undrained shear strength of Adapazari fine grained soils by cone penetration test

The main aim of the study is to provide a preliminary formula to estimate the reduction in shear strength parameters of gypseous soil exhibited when soaked in water. Experimental work has been conducted using direct shear test on undisturbed samples with three different gypsum contents 4 %, 28 %, and 42 %. Three different cases were considered, first is soil with its field water content (semi-dry), second after soaked with kerosene, and third after soaked with distilled water. The kerosene was used for comparison purposes substituting water for non-gypseous soils because it has low chemical interaction with gypsum. For semi-dry cases, results show proportional relationship between peak shear strength and gypsum content. However, the opposite holds true once submerged with water in which soil cohesion fades and the frictional angle is reduced to 72 %, 56 %, and 52 % respectively for the given gypsum content. A formula has been proposed that can be used by practitioners to estimate the reduction in the frictional angle based on the gypsum content of the soil.

This study includes determination of liquefaction potential in Erzincan city center. Erzincan Province is situated within first-degree earthquake zone on earthquake map of Turkey. In this context, the earthquake scenarios were produced using the empirical expressions. Liquefaction potential for different earthquake magnitudes (6.0, 6.5, 7.0) were determined. Liquefaction potential was investigated using Standard Penetration Test (SPT). Liquefaction potential analyses are determined in two steps: geotechnical investigations and calculations. In the first steps, boreholes were drilled to obtain disturbed and undisturbed soil samples and SPT values were obtained. Laboratory tests were made to identify geotechnical properties of soil samples. In the second step, liquefaction potential analyses were examined using two methods, namely Seed and Idriss (1971), Iwasaki et al. (1981). The liquefaction potential broadly classified into three categories, namely non-liquefiable, marginally liquefiable and liquefiable regions. Additionally, the liquefaction potential index classified into four categories, namely non-liquefiable, low, high and very high liquefiable regions. In order to liquefaction analysis complete within a short time, MATLAB program were prepared. Following the analyses, liquefaction potential index is investigated by Iwasaki et al. (1982) methods. At the final stage of this study, liquefaction potential maps and liquefaction potential index maps of the all study area by using IDW (inverse distance weighted) interpolation method in Geostatistical Analyst Module of ArcGIS 10.0 Software were prepared for different earthquake magnitudes and different depths. The results of soil liquefaction potential were evaluated in ArcGIS to map the distributions of drillings with liquefaction potential. The maps showed that there is a spatial variability in the results obtained which made it difficult to clearly separate between regional areas of high or low potential to liquefy. However, this study indicates that the presence of ground water and sandy-silty soils increases the liquefaction potential with the seismic features of the region.

Soil structure is the predominant factor of water, gases, and nutrients movement within the unsaturated zone. Despite the growing interest in the influence of structured soil media on soil-water dynamics, there is a gap in explicit technical documentation on monitoring soil hydraulic properties in undisturbed soil samples. This study proposes a new framework to measure and monitor soil hydraulic properties in undisturbed soil samples, in parallel optimizing falling head and centrifuge method for structured soil samples. Both unimodal and bimodal soil hydraulic functions are used to describe Soil Water Retention Curve (SWRC) data derived from laboratory experiments, and a modified one is introduced to integrate all the possible distinct pore domains of the soil matrix. The description SWRC data by the modified soil hydraulic equation coincides with Durner equation, while provides important insights on the saturated water content of each sub-pore domain. Water flow models in the unsaturated zone have been developed in Hydrus 1D, applying hydraulic parameters that correspond to soil hydraulic properties obtained from experimental data and the Rosetta Pedotransfer function. The combined used of optimized methods on undisturbed soil samples provided an insightful description of soil hydraulic properties, while water flow models with conceptualized soil hydraulic properties and data assimilation (DA) outperformed every other method. Water flow models using bimodal hydraulic function achieved the greater accuracy in each observation node of the soil column (10 cm: 0.074 cm 3 cm −3 , 50 cm: 0.0756 cm 3 cm −3 ).

The water retention curve (θ(ψ)), which defines the relationship between soil volumetric water content (θ) and matric potential (ψ), is of paramount importance in characterizing the hydraulic behaviour of soils. However, few methods are so far available for estimating θ(ψ) in undisturbed soil samples. We present a new design of TDR‐pressure cell (TDR‐Cell) for estimating θ(ψ) in undisturbed soil samples. The TDR‐Cell consists of a 50‐mm‐long and 50‐mm internal diameter stainless steel cylinder (which constitutes the outer frame of a coaxial line) attached to a porous ceramic disc and closed at the ends with two aluminium lids. A 49‐mm‐long and 3‐mm‐diameter stainless steel rod, which runs longitudinally through the centre of the cylinder, constitutes the inner rod of a coaxial TDR probe. The TDR‐Cell was used to determine the θ(ψ) curves of a packed sand and seven undisturbed soil samples from three profiles of agricultural soils. These θ(ψ) curves were subsequently compared to those obtained from the corresponding 2‐mm sieved soils using the pressure plate method. Measurements of bulk electrical conductivity, σa, as a function of the water content, σa(θ), of the undisturbed soil samples were also performed. An excellent correlation (R2 = 0·988) was found between the θ values measured by TDR on the different undisturbed soils and the corresponding θ obtained from the soil gravimetric water content. A typical bimodal θ(ψ) function was found for most of the undisturbed soil samples. Comparison between the θ(ψ) curves measured with the TDR‐Cell and those obtained from the 2‐mm sieved soils showed that the pressure plate method overestimates θ at low ψ values. The σa(θ) relationship was well described by a simple power expression (R2 > 0·95), in which the power factor, defined as tortuosity, ranged between 1·18 and 3·75. Copyright © 2011 John Wiley & Sons, Ltd.

The shear strength of the soil is a crucial factor in the structure's failure. Before any engineering structure is built on the soil, the shear strength characteristics must be thoroughly examined in order to reduce the calamity of structural collapse. The current study investigates the influence of varied percentages of fine material on soil shear strength. The soil sample consists primarily of sandy and clay soil. The study looked into the impact of fines on shear strength metrics (friction angle and soil cohesion). Several journal papers and articles were reviewed for this study. Based on the findings of several papers, the flow chart was created to describe the effect of the percentage of fine content in the soil and how it affects shear strength parameters. The shear strength parameters of sandy soil are significantly dependent on the percentage of fines in the mixture and the type of fine mineralogical composition. Both soil shear strength parameters increase at a substantial and apparent pace as compared to the particle content and additive increases in clay soil.

Sensitive marine clay in Ottawa is a challenging soil for geotechnical engineers. This type of clay behaves differently than other soils in Canada or other parts of the world. They also have different engineering characteristic values in comparison to other clays. Cone penetration testing in sensitive marine clays is also different from that carried out in other soils. The misestimation of engineering characteristics from cone penetration testing can result. Temperature effects have been suspected as the reason for negative readings and erroneous estimations of engineering characteristics from cone penetration testing. Furthermore, the applicability of correlations between cone penetration test (CPT) results and engineering characteristics is ambiguous. Moreover, it is important that geotechnical engineers who need to work with these clays have background information on their engineering characteristics. This thesis provides comprehensive information on the engineering characteristics and behaviour of sensitive marine clays in Ottawa. This information will give key information to geotechnical engineers who are working with these clays on their behaviour. For the purpose of this research, fifteen sites in the Ottawa area are taken into consideration. These sites included alternative technical data from cone and standard penetration tests, undisturbed samples, field vanes, and shear wave velocity measurements. Laboratory testing carried out for these sites has resulted in acquiring engineering parameters of the marine clay, such as preconsolidation pressure, overconsolidation ratio, compression and recompression indexes, secondary compression index, coefficient of consolidation, hydraulic conductivity, clay fraction, porewater chemistry, specific gravity, plasticity, moisture content, unit weight, void ratio, and porosity. This thesis also discusses other characteristics of sensitive marine clays in Ottawa, such as their activity, sensitivity, structure, interface shear behaviour, and origin and sedimentation. Furthermore, for the purpose of increasing local experience with the use of cone and ball penetrometers in sensitive marine clays in Ottawa, three types of penetrometer tips are used in the Canadian Geotechnical Research Site No. 1 located in south-west Ottawa: 36 mm cone tip, and 40 mm and 113 mm ball tips. The differences in their response in sensitive marine clays will be discussed. The temperature effects on the penetrometer equipment are also studied. The differences in the effect of temperature on these tips are discussed. Correlations between the penetrometer results and engineering characteristics of Ottawa's clays are verified. The applicability of correlations between the testing results and engineering characteristics of sensitive marine clays in Ottawa is also presented in this thesis. Two correlations from the Canadian Foundation Engineering Manual are examined. One of these correlations is between the N60 values from standard penetration testing and undrained shear strength. The other correlation is between the shear wave velocity measurement and site class. Temperature corrections are suggested and discussed for penetrometer equipment according to laboratory calibrations. The significance of the effects due to radical temperature changes in Canada and Ottawa is discussed. Some of the main findings from this research are as follows. • The Canadian Foundation Engineering Manual presents a correlation between standard penetration tests (SPTs) and the undrained shear strength of soils. This relationship may not be applicable to sensitive marine clays in Ottawa. • Another correlation between the site class, shear wave velocity, and undrained shear strength is presented by this same manual which may not be applicable to sensitive marine clays in Ottawa. • The rotation rate for field vane testing as recommended by ASTM D2573 is slow for sensitive marine clays in Ottawa. • Correction factors applied to undrained shear strength from laboratory vane tests may not result in comparable values with the undrained shear strength obtained by using field vane tests. • Loading schemes in consolidation or oedometer testing may affect the quality of the targeted results. • Temperature corrections should be applied to penetrometer recordings to compensate for the drift in the results of these recordings due to temperature changes. • The secondary compression index to compression index ratio presented in the literature may not be the value obtained from this research.

<p>The <sup>137</sup>Cs (t<sub>1/2</sub> =30 years) is a principal radioisotope that was artificially introduced into the environment through the atmospheric bomb tests took place from the middle of the 1940s to the 1980s and from the major nuclear accidents (i.e., Chernobyl, 1986 and Fukushima, 2011). From the atmosphere, <sup>137</sup>Cs easily adsorbs to particles and it returns to lithosphere (pedosphere) by wet and dry deposition as a radioactive fallout component. Due to the Chernobyl nuclear accident, the released contaminated air mass, containing Cs-137, largely propagated, deposited, and distributed across several European countries in the ambient environment (Balonov et al., 1996). These particles also reached houses (e.g. through open windows, cracks, and vents) in an urban environment and deposited inside resulting in the exposition of the habitants to <sup>137</sup>Cs, especially in areas that are not accessible for a regular cleaning like attics. Following the nuclear accidents, primary attention was drawn to agricultural areas and less attention was paid to urban environments. Accordingly, the goal of this study is to compare the <sup>137</sup>Cs activity in attic dust as undisturbed samples, and urban soils as disturbed environmental materials to determine the <sup>137</sup>Cs distribution in urban environment. </p><p>Attic dust (AD) samples were collected from 14 houses, which were built between 1900 and 1990 14 urban soil (US) samples were collected nearby the houses at a depth of 0-15 cm in Salgótarján, a former industrial city. To obtain a representative local undisturbed soil sample, a forest soil sample was collected from the upwind direction (NW) of the city. To check the <sup>137</sup>Cs content of the local industrial waste material, we also collected fly-ash slag sample from a waste dump.   AD and US samples were analyzed by a well-type HPGe and with an n-type coaxial HPGe detector in a low background iron chamber, respectively.</p><p>Cs-137 activity in the studied AD ranges from 5.51±0.9 to 165.9±3.6 Bq kg<sup>-1, </sup>with a mean value of 75.4±2.5 Bq kg<sup>-1 </sup>(decay corrected in 2016). In contrast, US samples show <sup>137</sup>Cs activity ranging between 2.3±0.4 and 13.6±0.6 Bq kg<sup>-1</sup>.  The brown forest soil sample has elevated <sup>137</sup>Cs activity concentration (18.5<strong>±</strong>0.6 Bq kg<sup>-1</sup>), compared to the urban soils. The fly-ash slags activity is below the detection limit (0.7±0.5 Bq kg<sup>-1</sup>).</p><p>The average <sup>137</sup>Cs activity in AD is ~15 times higher than that of US. This result clearly indicates that attic area provides a protected (hardly or unchanged) environment, therefore physical condition of the dust remains constant in time, and there is a small chance for chemical reaction. Forest soil proves that US were highly disturbed by anthropogenic activity. This is supported by fly-ash slag activity results.  Whereas, <sup>137</sup>Cs activity concentration of the AD samples shows significantly higher than that of the studied soils in Hungary. This confirms again US cannot show the historical atmospheric <sup>137</sup>Cs pollution such as attic dust. A statistically significant relationship (p=0.003, r<sup>2</sup>=0.05) were found between the AD and US samples. Therefore, it can be considered that attic dust remained undisturbed for decades and preserve past record of components of atmospheric pollution.</p><p> </p><p> </p>

The liquefaction susceptibility of four fine-grained soils in Charleston, South Carolina was examined primarily using cone penetration test (CPT) measurements. Ages of these four soils range from <6,000 years to about 30 million years. The liquefaction susceptibility criteria by Robertson and Wride appear to be adequate for the three younger soils, which are estuarine deposits. However, as noted previously by Li et al., the criteria incorrectly predict liquefaction susceptibility for the oldest soil, called the Cooper Marl. The Cooper Marl is a deep marine deposit that consists of 60-80% calcium carbonate and often classifies as MH to CH, based on the Unified Soil Classification System. The results illustrate the usefulness of also measuring pore water pressure during cone testing in fine-grained soils, for classification and liquefaction evaluation. A new CPT-based liquefaction susceptibility chart for screening out non-susceptible fine-grained soils is proposed.

With the growing trend of seeking resources, the significance of infrastructure construction in the upper part of soils has become increasingly prominent. Studying the geotechnical characteristics of soils is crucial for the safe operation of geotechnical projects and the efficient deep-resource development. The cone penetration test (CPT) indirectly measures the geotechnical properties of soils. However, Parkin and Lunne pointed out that the CPT data obtained solely on site cannot be reliably converted into soil mechanical parameters. It is difficult to obtain undisturbed samples of soils for laboratory tests (such as triaxial and pedometric tests), thus making it impossible to accurately obtain their mechanical parameters, resulting in a lack of comparison in the interpretation of in situ CPT data. Furthermore, due to the differences in testing procedures, experimental equipment, and soil types among various regions, the data and findings from CPT cannot be generalized into universal principles to guide engineering practices. CPT calibration chamber (CCC) testing, as an effective method to establish the correlation between laboratory measurements of soil and its in situ mechanical properties, holds significant research value for soils where undisturbed samples cannot be retrieved (such as cohesion-less sands and silty soils without plasticity). This paper first reviews the characteristics of large and small CCC equipment for different types of soil. It then discusses the boundary effect encountered in the interpretation of CCC test data and general solutions and summarizes the proposed empirical relationships based on CCC test data for geotechnical parameters. Finally, it outlines future directions for CCC equipment and data interpretation methods.

Infiltration outflow experiments, performed on undisturbed soil samples of coarse sandy loam taken in Korkusova Hut (KH) revealed the presence of preferential flow and steady state infiltration rate instability, compared to results of the same experiment performed on an undisturbed sample of fine sand taken in the Hupselse Beek, (HB) experimental watershed. The structure of soil samples was visualized by means of computer tomography, and in addition the infiltration outflow experiment for KH soil was performed in a magnetic resonance (MR) scanner. From MR images it was found that for the KH soil sample the character of flow changes gradually during the ponded infiltration. The volume flowing through the sample by gravity at the beginning of the experiment forming early outflow later decreases as the portion of the matrix flow increases. In the recurrent infiltration run into the saturated sample this decrease may be abrupt, accompanied by a significant decrease in the steady state infiltration rate. Both effects are unexpected from the point of view of Richards' theory.

Estimation of the soil–water retention curve, θ(h), on undisturbed soil samples is of paramount importance to characterise the hydraulic behaviour of soils. Although a method of determining parameters of the water retention curve (α, a scale parameter inversely proportional to mean pore diameter and n, a measure of pore size distribution) from saturated hydraulic conductivity (Ks), sorptivity (S) and the β parameter, using S and β calculated from the inverse analysis of upward infiltration (UI) has been satisfactorily applied to sieved soil samples, its applicability to undisturbed soils has not been tested. The aim of the present study was to show that the method can be applied to undisturbed soil cores representing a range of textures and structures. Undisturbed soil cores were collected using stainless steel cylinders (5cm internal diameter×5cm high) from structured soils located in two different places: (1) an agricultural loam soil under conventional, reduced and no tillage systems; and (2) a loam soil under grazed and ungrazed natural shrubland. The α and n values estimated for the different soils using the UI method were compared with those calculated using time domain reflectometry (TDR) pressure cells (PC) for pressure heads of –0.5, –1.5, –3, –5, –10 and –50kPa. To compare the two methods, α values measured with UI were calculated to the drying branch of θ(h). For each treatment, three replicates of UI and PC calculations were performed. The results showed that the 5-cm high cylinders used in all experiments provided accurate estimates of S and β. Overall, the α and n values estimated with UI were larger than those measured with PC. These differences could be attributed, in part, to limitations of the PC method. On average, the n values calculated from the optimised S and β data were 5% larger than those obtained with PC. A relationship with a slope close to 1 fitted the n values estimated using both methods (nPC=0.73 nUI+0.49; R2=0.78, P&lt;0.05). The results show that the UI method is a promising technique to estimate the hydraulic properties of undisturbed soil samples.