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The northern coastal strip of Venezuela with a semiarid climate presents conditions for the development of extensive areas with the presence of expansive clays, and, this is the main pathology of its communication routes due to deformation in the surrounding civil works. This contribution characterizes the presence of expansive clays in northern Venezuela in 81 samples distributed in several states of the country. The study included the determination of geomechanical properties through field work and laboratory tests by Atterberg limits, consistency indices and expansion tests as well as the relationship between the indexes and information from edometer tests. The soil grain size is mainly fine (silts and clays), in the Anzoátegui state the average content of fine grains is 86%, while in Falcón and Miranda they are a little lower, 82% and 67%, respectively. In general, the plasticity index (PI) of these expansive clays is high, with an overall average of 23, although the region of Falcón state presented a moderate average (18). The correlations between the expansion pressure and the PI showed a high correlation. These results corroborate that the criterion used to evaluate the Expansion Potential of a clay soil based on the PI proposed by Chen (1988), is a fairly adequate criterion to be used in the study and identification of the expansive behavior of these types of soils. [ABSTRACT FROM AUTHOR]

The creep index plays an important role in calculating the long-term settlement of natural soft clays, so it is vital to determine the creep index quickly and accurately. However, the prediction accuracy of the existing creep index models is low. This study presents seven gene expression programming (GEP) models by using different combinations of the liquid limit wL, plasticity index Ip, void ratio e and clay content CI as input variables for the prediction of creep index. A total of 151 datasets were collected from the available literature for building and testing the GEP models. The proposed GEP models were compared with two machine learning (ML) models (i.e., back propagation neural network and random forest) and five conventional empirical models in terms of three statistical indicators. The research results showed that the prediction performances of the two proposed GEP models (i.e., with combinations C I - w L - e and C I - I p - w L - e as input, respectively) surpass those of the five conventional empirical models and two ML-based models, recommended for predicting the creep index of natural soft clays in engineering practice. [ABSTRACT FROM AUTHOR]

Clay soils are widely used in constructing embankment dams, levees, highway embankments, sanitary landfills, and hydraulic barriers where they are compacted at maximum dry density and optimum water content. These structures are exposed to many cycles of wetting and drying during their service life, resulting in volume changes and developing shrinkage cracks. This study investigated the effect of density, water content, drying temperature, layer thickness, plasticity index, and multiple wetting and drying cycles on shrinkage crack parameters (length, aperture, and area). Five samples each of low-plasticity clay, medium-plasticity clay, and high-plasticity clay at water contents on both sides of optimum water content were compacted and then oven dried at temperatures of 10°C, 20°C, 30°C, 40°C, and 50°C. Upon complete drying, crack length, aperture, and area were digitally measured. Additionally, we saturated uncompacted clay layers of varying thicknesses (5, 7, 10, 20, and 30 mm) of the three clay types and oven dried them at the listed temperatures to investigate the effect of layer thickness on shrinkage crack parameters. The length, aperture, and area of the cracks were correlated with the influencing factors. Among the compacted samples, only high-plasticity clay samples developed shrinkage cracks, exhibiting an increase in crack length, aperture, and area with an increase in dry density and water content. For the uncompacted samples, crack length and crack area decreased with increasing layer thickness, whereas crack aperture increased. [ABSTRACT FROM AUTHOR]

Soil tensile strength is important in different geotechnical structures such as earth dams, roads, airports, landfills, and retaining walls. There are several experiments to study the tensile behavior of soils with different advantages and disadvantages. One of the methods used to investigate soil tensile behavior is tensile hollow cylinder apparatus, which has seldom been used. In this research, a hollow cylindrical device to measure the tensile properties of soil was built and operated. This device can apply tensile stress evenly to the entire soil sample so that stress concentration does not occur at any point in the sample. After designing, manufacturing, and assembling the apparatus, validation tests were performed to ensure the device was operating well. The results of the repeatability tests show the accurate performance of the device. Also, in this study, the effect of plasticity index (PI) on the tensile behavior of kaolinite clay was investigated. Clayey soils with plasticity indices of 10 and 24% were selected. The results show that for clays with a similar mineral, the tensile strength increases and the tensile failure strain decreases with increasing the plasticity index.

A study on the effect of sisal fibre and waste plastic strips on tropical black clay (also called Black cotton soil, BCS) was carried out. Tests piloted on the natural and treated soil consist of California bearing ratio (CBR), Atterberg limits and compaction for different percentages inclusion of sisal fibre (0, 0.5, 1, 1.5 and 2%) and waste plastic strips (0, 0.5, 1, 1.5 and 2%) by dry weight of soil. Results obtained showed that the liquid limit of BCS initially fluctuated between 43.4% and 55.9% at 1% sisal fibre content, then dropped to 49.4% at 2% sisal fibre content. In the case soil treated with waste plastic strips, liquid values increased from 43.4% for the natural soil to a highest value of 58% at 1% waste plastic strips and thereafter decreased to 49.15% at 2% waste plastic strips content. Plastic limit for both BCS-sisal fibre/waste plastic strips initially decreased from its natural value of 25.78 to 15.55 and 14.77% when treated with sisal fibre and waste plastic strips respectively at 0.5% admixtures content. In the case of plasticity index, values initially increase from its natural value of 17.66% to peak values of 35.39 and 43.23% for sisal fibre and waste plastic strips treated soil respectively, and thereafter decreased. Maximum dry density (MDD) initially increased from 1.55 mg/m3 at 0%, to 1.60 mg/m3 at 0.5% and thereafter decreased to 1.53 mg/m3 at 2% of fibre content. In the case of samples treated with waste plastic strips. The MDD progressively increased as the amount of waste plastic strips increased. OMC show an overall trend of increase for BCS treated with sisal fibre, and a general trend of decrease for soil treated with waste plastic strips. The CBR values initially lessened from their natural value of 13.59% to 4.76% at 1% sisal fibre and subsequently increased to 10.57% at 2% sisal fibre. Similar behaviour was observed for soil modified with waste plastic strips. Based on the results, BCS/waste plastic strips improved the soil more than BCS/sisal fibre treated soil and is recommended at optimal 2% waste plastic strips for geotechnical engineering application such as road payment. [ABSTRACT FROM AUTHOR]

Intrinsic soil properties, such as the Atterberg limits, are essential factors influencing the mechanical behaviour of the fine-grained soils. In this study, a series of long-term multiple-stage loading oedometer tests were performed on alluvial organic soils to investigate the creep behaviour. The plasticity ratios ranged from 0.4 to 0.63. The smaller value of the plasticity ratio Rp indicated higher soil plasticity. The results showed that the coefficient of secondary compression Cαe of alluvial organic soils was stress- and strain-rate-dependent. The coefficient of secondary compression change index m was derived using a double-logarithmic approach for a creep degradation and was related to the plasticity and clay percentage to fines. Based on the results, it was found that high plasticity soils exhibit slow creep degradation rate during one-dimensional straining under normally consolidated state. The results show that the higher soil plasticity expressed by the plasticity index, plasticity ratio and clay percentage to fines, smaller the coefficient of secondary compression change index. Moreover, the correlations among a soil plasticity properties and creep parameters for the alluvial soils have also been proposed. [ABSTRACT FROM AUTHOR]

Purpose. To determine and evaluate some ceramic properties (plasticity index, linear shrinkage, porosity, and bulk density) of clay deposits from Anambra Basin of South Eastern Nigeria. Methods. Fifteen clay samples were collected by trenching methods. Samples were tested for plasticity index, linear shrinkage, loss on ignition, porosity, and bulk density using test standards developed by the American Society of Test and Materials. Result data were evaluated using tabulation and statistical graphs. Findings. Mean plasticity index of the samples range from 14.3 to 21.3. Mean linear shrinkage is from 2.5 to 5.5%. Mean loss on ignition is from 6.56 to 9.75%. Mean porosities is from 6.9 to 30.1%. Mean bulk density is between 2362 and 1692 kg/m3. The ceramic properties of the deposits varied across location, and no single deposit has the complete set of ceramic properties needed in ceramic industries. Originality. To the best of the authors' knowledge, this is the first research that looked into the distributions of ceramic properties of clay deposits in Anambra geologic Basin. Practical implications. The findings will help investors to make informed decisions on clay deposits in their investment plans and can be used as supporting document when applying for mining titles. [ABSTRACT FROM AUTHOR]

In an attempt to develop a database of the cyclic resistance of fine-grained soils in Indonesia a series of cyclic triaxial test was performed on fine-grained soils collected from two locations near shore of north Java Island, Indonesia. These samples were classified as fine-grained soils with clay-like behavior and, according to various liquefaction criteria, they are non-liquefiable. Our study used a cyclic triaxial test to apply multistage cyclic axial stresses in a form of sinusoidal stress with a frequency of 1 Hz. All specimens are isotropically consolidated passing their preconsolidation stress in order to achieve a normally consolidated state with OCR of about 1. Our findings suggest that cyclic resistance of North Java clay-like fine-grained soils follows the SHANSEP concept and could be normalized at OCR of 1. At fifteen cycles of uniform sinusoidal loading the tested clay and silt samples have a normalized cyclic strength, (qcyc/2)/𝜎c′, or a cyclic resistance ratio (CRR) of approximately 0.31 and a cyclic strength ratio, (qcyc/2)/su, of 0.70. [ABSTRACT FROM AUTHOR]

Settlement of structures is determined by the stiffness of the soil where they are built. Compression index (c c) quantifies the compressibility of the soil and is a key parameter in the design of geotechnical structures. To predict the value of c c in clay soils, a global database of more than 1000 data points was collected and analysed. Liquid limit, plasticity index, natural water content, and initial void ratio were considered as predictor variables. A super-learner machine learning model was developed to predict c c from these variables. The model demonstrated a reasonable predictive performance and was subsequently integrated into an online tool. Additionally, four symbolic regression expressions were obtained to relate c c with some of the input variables when not all data are available, providing simple and practical alternatives for c c , estimation. This study provided two major contributions: (1) the non-local nature of the data expands the scope and generalizability of the findings, and (2) the availability of the proposed algorithm through an online application ensures its accessibility for geotechnical engineers, enhancing the work's practical applicability and intrinsic value. • Prediction of compression index from liquid limit, plasticity index, water content and void ratio. • Over 1000 data points worldwide were collected to predict compression index value in clays. • Optimized ensemble of three ML models offers reliable compression index estimates. • The online tool developed aids engineers in estimating the compression index from soil parameters. • Symbolic regression expressions are proposed for use when full data is unavailable. [ABSTRACT FROM AUTHOR]

The present paper presents different approaches which includes plasticity based criteria that helps in distinguish between liquefiable and non-liquefiable soils deposits having fine content. A brief review of the previous work has been mentioned to emphasise on the need of new parameters for liquefaction susceptibility of clayey soils. Clay content, liquid limit and water content are considered as key parameters that helps in liquefaction assessment. Several recommendations proposed by prominent researchers are described here to present wide range of plasticity index, liquid limit and other parameters that affects liquefaction behaviour of clayey soil significantly. But the differences in the range of plasticity index leads to confusion and misperception in determination of liquefaction susceptibility of fine grained soil. One of the high seismic zone site is analyzed using different approach which consider fine content of soil mass. It is found that for a better and proper segregation of the layers Bray and Sancio criteria may be adopted which uses plasticity as one of its input parameter and clearly differentiate site in between liquefiable, non-liquefiable and sites that may liquefy i.e. moderately liquefiable. This summarizes that plasticity is one of the significant criteria which draws a clear differentiating line between liquefiable and non-liquefiable soil deposits. [ABSTRACT FROM AUTHOR]

Consistency limits are essential and simple design parameters that are utilized as standard entries of all kinds of soil investigation programs conducted for geotechnical projects which are constructed in/on fine grained soils. These limits also represent mineralogical and physical properties of clayey soils directly and used to estimate their strength and rigidity properties indirectly. However, the consistency tests are assumed as the simple and basic tests of geotechnical engineering investigations, but the effects of operator, calibration of the device and environmental aspects at the tests damage the reliability and correctness of results. In this paper, it is aimed to overcome these challenges by evaluating the consistency characteristics of clayey soils considering only the values of liquid limit of specific clays with the use of simple regression analysis. A database is prepared by using 500 soil investigation reports that are involving the site characterization information, laboratory and field tests of Istanbul Province European side clayey soils, including Avcılar, Esenyurt, Küçükçekmece, Büyükçekmece, Çatalca, Zeytinburnu, Bahçelievler, Bakırköy districts. 1523 liquid limit tests are obtained from the mentioned database for high and very high plastic clays. The regression analyses have been applied to query the parameter effect ratio on the consistent characteristics and relationships have been tried to be developed to evaluate the values of plastic limit and plasticity index directly from only liquid limit test applications. The effects of fine material content, depth and natural water content is also investigated. Verifications of the suggested equations have been done for different cases and comparisons are made with the well-known sources of literature. Consequently, strong equations are acquired to determine the plasticity index value in terms of liquid limit, liquid limit-depth, liquid limit-fine content, natural water content-fine content respectively based on the actual experimental tests conducted in Istanbul. [ABSTRACT FROM AUTHOR]

Samples of clay deposits in Obudu and its environs, southeastern Nigeria were evaluated to establish their potential for industrial use. Geochemical, mineralogical and geotechnical properties were employed in assessing the suitability of the clay deposits for potential industrial uses. Mineralogical analyses reveal kaolinite as the dominant clay mineral with quartz as the dominant non-clay mineral. The physical and geotechnical properties indicate that the hydrous and marginal expansive clays are fine-grained (75 μm > 2%), have low to medium plasticity (plasticity index 12.8–40.8%), low density (1.69 to 2.60 g/cm3) and low linear shrinkage (4–6%) on drying and firing. Geochemical analysis shows significant amounts (> 1.0 wt%) of SiO2, Al2O3, Fe2O3, MgO, CaO, and Na2O, and relatively low values (< 1.0 wt%) of K2O, FeO and TiO2. The clays meet the requirements for production of building bricks, roofing tiles, local pottery products and domestic ceramic wares other than ceramic white wares. However, these low grade clays will require a high degree of refining or beneficiation to remove the undesirable minerals to qualify for use in rubber, paper, paint and cosmetic industries. [ABSTRACT FROM AUTHOR]

This study presents the effect of high plasticity on swell potential, swelling pressure and micro-structural characteristics of kaolinite-bentonite mixed clays. Five different mix ratios of kaolinite bentonite mixture of 100:0, 90:10, 75:25, 50:50 and 25:75 in % by weight of dry kaolinite were used. All five synthesised soils were then mixed with 0%, 5% and 8% of cement by weight of dry soil, cured for 28 days and subjected to the Atterberg limit, one-dimensional oedometer and scanning electron microscope test. The inclusion of 5% and 8% cement reduces the plasticity index of the treated soils as the percentage of bentonite increases. The effects on plasticity of treatment with 5% and 8% cement after a 28-day curing period was evaluated, and the results show that reduction in plasticity index resulted in decreased swell potential and swelling pressure of the kaolinite-bentonite mixed clays. The results of microstructural analysis of 5% cement-treated soils show formation of flocculated fabric and cementation of soil particles, and filling with cementitious compounds of the voids of flocculated fabric in the soil. The reduction in swell can be attributed to the resulting compacted and dense mass of treated soils due to cementation of soil particles and cation exchange. The complex swell behaviour of high-plasticity kaolinite-bentonite mix is explained using the one-dimensional oedometer test, by further experimental study and examination of the microstructure of treated soils. [ABSTRACT FROM AUTHOR]

To establish the evaluation method of intrinsic compressibility, oeodemter test was performed on Zhuozi clay and Wuqing clay and some other test data of various kinds of reconstituted clays were collected from the previous literatures. The compressibility constants (void ratio at vertical stress of 100 kPa) and (compression index) are widely recognised as indicators of intrinsic compressibility. Therefore, the influencing mechanisms of index properties can be investigated by establishing correlations with and. It has been found that and have linear relationships with liquid limit and normalised initial water content. Therefore, and can be quantitatively evaluated in terms of liquid limit and initial water content. Since plasticity index is the third factor that can slightly affect intrinsic compressibility, it can be used to modify the calculated value of and. It is indicated that liquid limit, initial water content and plasticity index are all index properties that can affect intrinsic compressibility, based on which and can be calculated and finally the compression curves can be evaluated based on the intrinsic concept. [ABSTRACT FROM AUTHOR]

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Clays are key elements not only in geological and environmental processes, but also in many human activities. To differentiate clays from other soils, AIPEA and CMS highlight plasticity as the clays' most distinctive characteristic. However, the lack of any reliable plasticity yardstick makes the particle-size-criteria to be more widespread. In a previous work, the authors found some innovative ratios between the plasticity index (PI) and the liquid limit (LL) which allowed the clays' boundary to be established according to a plasticity basis. As plasticity is directly associated with toughness, different published data containing valuable information have been processed in this study by plotting toughness values against PI/LL ratios. In this way, the soundness of the previous authors' finding has been checked. It is demonstrated that a fine-grained material can be defined as a clay when PI ≥ LL/2, while a material is moderately or slightly clayey if LL/3 < PI < LL/2, such that when PI ≤ LL/3 the influence of clay minerals is much reduced. Apart from an updated classification of soil for engineering purposes, a new textural soil classification is presented, alternative to the USDA one, which allows the real nature of a soil to be known accurately by means of plasticity tests and simple sieving instead of particle-size sedimentation methods. [ABSTRACT FROM AUTHOR]

A model for pore water pressure accumulation and settlement of saturated clay layer induced by uniform and irregular cyclic shear strains was developed by concerning the direction of cyclic shear strain. To apply this model to any kinds of clay, the effects of Atterberg's limits of cohesive clay on the cyclic shear-induced pore water pressure and the settlement were observed by using the strain-controlled cyclic simple shear test apparatus which can control the cyclic shear direction. In conclusion, the effects of Atterberg's limits of clay on the cyclic shear-induced pore water pressure accumulation and settlement were clarified by using the cumulative shear strain. Based on the experimental results, estimation methods for the pore water pressure accumulation and post-cyclic settlement of clay with a wide range of Atterberg's limits were developed. Furthermore, to apply the proposed methods to the earthquake-induced ground motions, a transformation procedure of irregular cyclic shears to the equivalent uniform ones including the effect of cyclic shear direction was developed and the practical applicability was confirmed. [ABSTRACT FROM AUTHOR]

The change in the shear modulus of clays under repeat environmental loads is an important factor in the design of offshore and onshore foundations. A degradation model for the shear modulus of soft clays that considers the effects of the number of cycles, the cyclic stress ratio, the loading frequency and the plasticity index is proposed. A series of undrained cyclic triaxial tests on undisturbed Shanghai marine clays were conducted. Experimental results reveal that the shear modulus degradation index has a logarithmic relationship with the number of cycles, decreases linearly with the cyclic stress ratio, and increases linearly with the loading frequency when plotted in log-log coordinates. Further study using existing data from other research shows that the degradation index decreases with plasticity index, I P . Based on the test results, a new degradation model is proposed which considers these factors explicitly. The main feature of the new model is that only one set of parameters for each type of clay is required for the prediction of shear modulus degradation. The applicability of the present model is verified by five soft clays with different plasticity indices and loading conditions. [ABSTRACT FROM AUTHOR]

An estimation method for earthquake-induced pore water pressure and the post-earthquake settlement of soft clay was developed by focusing on its Atterberg's limits and the direction of cyclic shearing. To clarify the fundamental characteristics of clays with different Atterberg's limits under multi-directional cyclic shear, normally consolidated specimens of Kaolinite clay, Tokyo bay clay and Kitakyushu clay were subjected to cyclic simple shear under the undrained condition with various cyclic shear directions and shear strain amplitudes, followed by the dissipation of cyclic shear-induced pore water pressure. The effects of undrained cyclic shear on the pore water pressure accumulation and post-cyclic settlement were observed, and relationships with Atterberg's limits were then investigated. In conclusion, the pore water pressure accumulation and post-cyclic settlement induced by multi-directional cyclic shear increase considerably to a higher level compared with those generated by the uni-directional one and such a tendency is evident for clays with a wide range of Atterberg's limits. Comparisons of the results indicate that the soil with higher plasticity index shows the lower pore water pressure accumulation and post-cyclic settlement, irrespective of number of strain cycles and shear strain amplitude. Based on these results, a model for earthquake-induced pore water pressure and post-earthquake settlement was developed by incorporating the Atterberg's limits as a function of experimental constants and the practical applicability was confirmed. [ABSTRACT FROM AUTHOR]

The definition of active porosity given by B.N. Gumenskii is revised. The active porosity is taken to mean the bulk porosity less the pore space volume occupied by adsorbed water. The methods of calculating the active porosity discussed in the paper are based on finding the adsorbed-water volume at the maximal airdry moisture of soil and subtracting this value from the bulk porosity. The active porosity is shown to be important for assessing the reservoir and infiltration soil properties and a number of other characteristics used in soil mechanics. [ABSTRACT FROM AUTHOR]

This paper investigates the cyclic and post-cyclic shear behavior of low-plasticity silt and the impact of additional clay content. Bentonite clay was added to the low-plasticity Mississippi River Valley (MRV) silt (PI=6) to increase the clay content of the soil. A series of triaxial tests were conducted in the laboratory to examine the shear and pore pressure behavior during and after cyclic loading. As the bentonite content in the reconstituted specimens increased, the excess pore pressure developed at a slower rate and the total excess pore pressure decreased at the end of cyclic loading. In contrast to the MRV silt, the specimens modified with bentonite experienced cyclic softening rather than initial flow liquefaction. The cyclic shear strength increased with an increase in bentonite content. The post-cyclic reconsolidation behavior was a similar to a virgin compression process, and not recompression. Adding bentonite to the MRV silt results in changes in permeability, compressibility, undrained shear strength, and initial stiffness. Additionally, the cyclic loading had a marked effect on the shear behavior of low-plasticity soil with a PI<6, but not noticeable with a PI>6. This study suggests that the behavior of the Mississippi River Valley silt changes from contractive sand-like material to clay-like behavior at a PI≈6 due to the addition of clay. [ABSTRACT FROM AUTHOR]

Landslides and slope failures in natural clay-rich materials are frequently observed in coastal areas and other areas where these materials were deposited in a saline water environment. High sodium chloride (NaCl) concentration in the pore fluid results from deposition in this environment. As shown by the results of this study, subsequent reduction in the NaCl concentration results in reduction in fully softened shear strength, with potentially significant reduction in slope stability. Fourteen sample materials were collected from seven different landslide areas in Niigata Prefecture, Japan, to evaluate the effect of saline water on fully softened shear strength (FSSS). The sample materials were collected from the intact mudstones and the sliding surface materials. Pore waters from the powdered sliding surface materials exhibited low concentrations of NaCl; however, the pore waters in the powdered intact rock samples exhibited a high concentration of NaCl. Washing of NaCl from the powdered intact rock samples caused a significant drop in FSSS, whereas mixing the sliding surface materials with NaCl at 0.5-M concentration increased the FSSS of the samples significantly. To evaluate the effect of saline water on various types of clay minerals, 12 samples-nine with montmorillonite as the clay mineral and three with kaolinite as the clay mineral-were prepared in the laboratory, and Atterberg limits and FSSS of these mineral mixtures were measured. There was a significant increase in the FSSS when the mineral mixtures with more than 9.5% montmorillonite were tested with saline water. The effect was negligible or negative for mineral mixtures having 9.5% or less montmorillonite content and any amount of kaolinite. An excellent correlation was observed between the liquid limits, plasticity indexes, and corresponding fully softened friction angles irrespective of the type of pore water. Likewise, there was a good correlation between the ratios of the liquid limits and plasticity indexes measured with different pore waters and the corresponding ratios of the fully softened shear strengths. It was observed that the reduction in FSSS of powdered intact rock with NaCl leaching could reduce the calculated factor of safety of the landslides by more than 0.3, demonstrating the negative effect of NaCl leaching from the slope materials on the stability of slopes. [ABSTRACT FROM AUTHOR]

Abstract: To evaluate the behavior of cohesive soil reinforced with a geotextile, 144 unconfined and 72 unconsolidated–undrained (UU) triaxial compression tests were conducted. The moisture content of soil during remolding, relative compaction, soil type, confining pressure, type and number of geotextile layers were all varied so that the behavior of the sample could be examined. The results provide evidence that as the moisture content increases, the peak strength of both the reinforced and unreinforced samples decreases and the axial strain at failure increases. Moreover, with increasing relative compaction the peak strength of the sample and axial strain at failure increases, whereas the peak strength ratio decreases. The peak strength ratio is the ratio of the peak strength of the reinforced samples to that of the unreinforced samples. For soils with low plasticity indices the main cause of the increase in the strength is the increase in the cohesion of the reinforced sample. However, in soils of higher plasticity index, as the number of geotextile layers increases, the internal friction angle of the reinforced samples increases. [Copyright &y& Elsevier]

Abstract: Hydraulic conductivity is one of the important, basic engineering properties of soils. However, as a soil parameter it is difficult to measure and can be highly variable, necessitating the investigation of a large number of samples. For these reasons several researchers have proposed various indirect methods for predicting the hydraulic conductivity of soils from easily measured and routinely obtainable data. As plasticity is the most distinctive and the easiest property of clays to measure, it would be a very convenient basis for predicting the hydraulic conductivity. This paper focuses on an investigation of the relationship between the hydraulic conductivity of clays and their Atterberg limits. For this purpose five samples of expanding and non-expanding clays were used. The results of laboratory tests showed that the hydraulic conductivity of a clay at a selected void ratio could be adequately determined when the external surface area of the clay grains was considered. The finding that there exists an exactly defined relationship between the Atterberg limits of clays and their external specific surfaces helped us to express the hydraulic conductivity in terms of the void ratio and the plasticity value. [Copyright &y& Elsevier]

Site investigations of the soils are considered very important for evaluation of the site conditions, as well as the design and construction for the project built in it. Taihu tunnel is thus far the longest tunnel constructed in the lake in China, with an entire length of over 10 km. However, due to the very insufficient site data obtained for the lacustrine clay in the Taihu lake area, a series of self-boring pressuremeter (SBPM) field tests was therefore carried out. Undrained shear strengths were deduced from the SBPM test, with the results showing generally higher than those obtained from the laboratory tests, which may be attributed to the disturbance to the soil mass during the sampling process. Degradation characteristics of the soil shear modulus (Gs) were mainly investigated, via a thorough comparison between different soil layers, and generally, the shear modulus would cease its decreasing trends and become stable when the shear strain reaches over 1%. Meanwhile, it was found that a linear relationship between the plasticity index and the shear modulus, and between the decay rate of the shear modulus and the plasticity index as well, could be developed. Further statistical analysis over the undrained shear strength and shear modulus distribution of the soils shows that the undrained shear strength of the soils follows a normal distribution, while the shear modulus follows a log-normal distribution. More importantly, the spatial correlation length of the shear modulus is found much smaller than that of the undrained strength. [ABSTRACT FROM AUTHOR]