Prediction of undrained shear strength and correlation in between soil parameters

Engineering properties of soils, collected from different sites designated for the erection of telecommunication towers, were obtained and analyzed. Probability distribution functions were fitted to this properties. Probability distribution function were fitted to this properties to predict the incidences of their occurance.. Correlation analysis also carried out to check for the relationships if any between the properties. A linear relationship was observed between plastic index and liquid limit, saturated unit weight and angle of internal friction, saturated unit weight and dry unit weight, degree of saturation and water content,saturated unit weight and cohesion, saturated unit weight and dry unit weight. The void ratio,bulk unit weight and dry unit weight were found to follow normal distribution; water content, liquid limit and plasticity index followed the gamma distribution; gravity specification, porosity, saturation, angle of internal friction and cohesion fitted weibull distribution and saturated unit weight fitted log-normal distribution. The study also found that porosity and void ratio have high probability of occurance at their threshold levels. This indicates an unfavorable condition for the soil at this sites

This research paper is aimed to briefly highlight the correlation between unconfined compressive strength and point load index for jointed rocks based on joint asperity & orientation. In this observe, specimens were tested to obtain their unconfined compression strength and point load index for a different joint condition. The different joint conditions considered for this study were clean joint and joint filled condition. For both clean joint and joint filled specimens were prepared by various asperity angles of 30°, 45°, 60° and 90° with different orientation angles such as 0°, 30°, 45°, 60°, 90°. Plaster of Paris was used as model material to simulate weak rock mass in the field. By testing intact model specimens for unconfined compressive strength leads to revealing of optimum moisture content for further testing. The curing period for the model specimens is 3 days at room temperature. To simulate jointed rocks, various moulds of different orientation of joint with respect to major principal stress are prepared separately. The inner diameter of the mould is 50 mm and height is 100 mm. After casting, a rough joint was created by cutting the prepared sample using the cutter. The specimens are tested for both clean joint and joint filled condition to determine the favorable joint orientation and asperity angle. After curing, the specimens are tested for unconfined compressive strength and Point load index. The new multi-linear correlation for determining unconfined compressive strength with the help of point load index is developed and cross checked with equations formed for actual rock. On comparing both results it is found that the new equation can suitable for assessing the unconfined compressive strength of limestone and serpentinite rocks through point load index value.

In this paper, stress-strain behaviour of sand-clay mixture stabilised with different cement and rice husk ash percentages, and reinforced with different polypropylene fibre lengths are evaluated. Mixtures are widely used in road construction for soil stabilisation. It is observed that replacing half of the cement percentage (in high cement contents) with rice husk ash will result in a higher unconfined compressive strength. In addition, the presence of 6 mm polypropylene fibres will help to increase the unconfined compressive strength of stabilised samples, while larger fibres cause reverse behaviour. In addition, introducing a new index for assessing the effect of curing days. Curing Improvement Index it is obtained that larger fibres show higher Curing Improvement Index values. Results gained for the effects of curing days, and fibre lengths are further discussed and interpreted using Scanning Electron Microscopy photos. Based on the conducted Unconfined Compressive Strength, Indirect Tensile Strength, and Flexural Strength tests and using evolutionary polynomial regression modelling, some simple relations for prediction of unconfined compressive strength, indirect tensile strength, and flexural strength of cement-rice husk ash stabilised, and fibre reinforced samples are presented. High coefficients of determination of developed equations with experimental data show the accuracy of proposed relationships. Moreover, using a sensitivity analysis based on Cosine Amplitude Method, cement percentage and the length of polypropylene fibres used to reinforce the stabilised samples are respectively reported as the most and the least effective parameters on the unconfined compressive strength of specimens.

Stabilization of sand by the deep mixing method increases its unconfined compressive strength (UCS) so that it can be used as a foundation for infrastructure. This paper presents research work on physicomechanical properties of soil–cement columns installed in the central area of Vietnam, which consists of sandy clay, fine sand, medium sand, and coarse sand. Two types of cement were mixed with these soils in amounts of 150–350 kg/m3 at a water-cement ratio of 0.6. Approximately 80 soil–cement samples were prepared and cured at standard moist conditions and then tested for unconfined compressive strengths and flexural strengths at 7, 14, 28, and 56 days. The maximum unconfined compressive strength of the soil–cement was 10 MPa after 56-day curing for the coarse sand mixed with 350 kg/m3 cement. The Bayesian Model Averaging and the Principal Component Analysis Methods were used to evaluate the influence of different variables on the UCS of the cement-stabilized soil. The analysis shows that the UCS of the soil–cement depended on the contents of SiO2, SO3, K2O in the soil, the soil grain size, the cement content, and the curing time. The prediction equations allow the determination of unconfined compressive strength and flexural strength of cement-stabilized sand by the wet mixing method used as a ground improvement method for foundations.

This paper develops probabilistic predictive models for the unconfined compressive strength of intact rock based on the point load strength tests. A database of point load strength and unconfined compressive strength measurements for sedimentary, igneous and metamorphic rocks is first developed. The measurements are corrected to their standard equivalent values, namely unconfined compressive strength and point load strength for specimens with 50 mm diameter. A Bayesian framework is used to assess different candidate model forms and to estimate the corresponding model parameters. This Bayesian approach uses the prior information for the values of the unconfined compressive strength and point load strength measurements to develop an unbiased method for prediction of unconfined compressive strength based on point load strength tests. The Bayesian estimation of the model parameters accounts for the relevant sources of uncertainty including aleatory and epistemic uncertainties and for possible measurement errors in the point load strength test data. Probabilistic models are developed for sedimentary, igneous and metamorphic rocks. It is found that (i) a model of form provides the best fit to the laboratory data, and (ii) accounting for measurement errors and separating the database into subgroups based on different rock types decrease the model uncertainty.

The accurate prediction of unconfined compressive strength (UCS) in rock samples is critical for the successful planning, design, and implementation of mining and civil engineering projects. UCS is crucial in assessing the stability and durability of rock masses, which directly influences the safety, efficiency, and cost-effectiveness of construction and excavation operations. Here’s a refined version of your text for enhanced clarity and flow: in this part, the execution of the proposed model was compared for both single and hybrid configurations. Hybrid models included support vector regression (SVR) combined with the Seahorse Optimizer (SVSH) and SVR combined with the COOT optimization algorithm (SVCO). For training, 70% of the UCS dataset was utilized, while the remaining 30% was equally divided between testing (15%) and validation (15%). For the model evaluation, several metrics were considered in this work, including the R2, RMSE, WAPE, MAE, and RAE, which ensure fairness in the analysis. The closer the R2 value comes to 1, the better the performance. The error metrics should be close to 0 for better accuracy. From Table 2, one can observe that the result of the standalone SVR model gave an RMSE of 6.213 during training and 9.454 during testing, hence showing poor performance. However, the inclusion of optimization algorithms significantly improved the performance of the SVR framework. Among the hybrid models, the SVSH model had the best performance, with an R2 value of 0.998 and an RMSE of 1.261 during training. The SVCO model performed moderately, with an R2 value of 0.988 during training.

Ultrabasic rocks show a variety of engineering properties that may affect quarrying operations, tunnelling, mining, slope stability and the use of rock as a construction material. The physico-mechanical properties are influenced by the mineralogical and textural characteristics as well as the weathering of the rock. For this reason, the relationships between petrographic and physico-mechanical properties of fresh (peridotites) and serpentinized (serpentinites) ultrabasic rocks from central Greece, were investigated using correlation analysis. Thin sections, from the 47 samples, were prepared and examined under the polarizing microscope with the aim of describing the main mineralogical composition, the grain size, the serpentinization percentage and the structure of the rocks. The mineralogical and textural characteristics of some of them were also studied by X-ray diffraction analyses and the scanning electron microscope. The 47 samples were tested to determine dry and saturated unit weight, effective porosity, uniaxial compressive strength and static modulus of elasticity. The relationships between these properties and the petrographic characteristics are described by simple regression analyses. The research demonstrates that the physico-mechanical characteristics are strongly influenced by the petrographic characteristics except for mineral grain size. Negative linear correlations exist between serpentinization percentage and dry unit weight, while the effective porosity has a strong positive relationship with degree of serpentinization. Positive relationships are also obtained between the mechanical properties and dry unit weight and micropetrographic index Ips, while the increase of effective porosity causes a decrease in the index Ips (logarithmically in peridotites, and exponentially in serpentinites). The mechanical properties are exponentially related (negatively) to the serpentinization percentage in serpentinites and logarithmically (negatively) in peridotites. The serpentine plays a very important role in strength and elasticity modulus reduction, while the primary minerals have a smaller effect on the mechanical properties.

Development of insulating backfill materials produced from the ternary mixtures of red mud, fly ash and preformed foam

Influence of freeze–thaw on engineering properties of a silty soil

The shear strength of soil is one of the most important soil properties that should be identified before any foundation design. The presence of gypseous soil exacerbates foundation problems. In this research, an approach to forecasting shear strength parameters of gypseous soils based on basic soil properties was created using Artificial Neural Networks. Two models were built to forecast the cohesion and the angle of internal friction. Nine basic soil properties were used as inputs to both models for they were considered to have the most significant impact on soil shear strength, namely: depth, gypsum content, passing sieve no.200, liquid limit, plastic limit, plasticity index, water content, dry unit weight, and initial voids ratio. Multi-layer perceptron training by the backpropagation algorithm was used in creating the network. It was found that both models can predict shear strength parameters for gypseous soils with good reliability. Sensitivity analysis of the first model indicated that dry unit weight and plasticity index have the most significant effect on the predicted cohesion. While in the second model, the results indicated that the gypsum content and plasticity index have the most significant effect on the predicted angle of internal friction.

The aim of this study was to model the Undrained Shear Strength (USS) of soil found in the coastal region of the Niger Delta in Nigeria with some soil properties. The undrained shear strength (USS) is a key parameter needed for most geotechnical/structural designs. Accurate determination of the USS of soft clays can be challenging to obtain in the laboratory due to the difficulty in remoulding the clay to its in-situ conditions before testing and more accurate test such as Cone Penetration test (CPT) can be quite expensive. This study was carried out at Escravos site which is located in Delta state, Nigeria. Three Boreholes were drilled and soil samples were collected at 0.75 m intervals up to a depth of 45 m. Laboratory tests were used to obtain the moisture content, bulk unit weight, liquid and plastic limit, while CPT was used in obtaining the undrained shear strength. Classification of the soil samples was done by adopting the Unified Soil Classification System and various models relating the USS with the soil properties were developed. The result showed that most of the soils at Escravos site were predominately inorganic clay of high plasticity which are problematic due to the expansion and shrinking nature of this type of soil. The model developed showed that the soil properties that gave the best fit with the USS were the moisture content and effective stress of the soil. The coefficient of determination (R2) and the root mean square error (RMSE) obtained for this model were 0.805 and 6.37 KN/m2, respectively.

This study is to analyze geotechnical properties and biological status of undisturbed municipal solid waste (MSW) associated with depth by using a large-diameter borehole sampling method. Through the method, a 28 m-borehole with 0.8 m of the diameter was drilled into the MSW body consisting of ten-lift layers of waste placed over 4000 days in an operating landfill. MSW sample cuttings were collected from the field site, weighted, and transferred to a laboratory for additional experiments to measure various properties such as moisture content, constituent characterization, unit weights, specific gravity, decomposition state, saturation, and compression rates with regard to waste depth. Also, the methane production obtained from MSW decomposition tests indicated that waste mass was relatively consistent throughout the depth of borehole and had not reached the accelerated production phase of methane. The wet and dry unit weights of the MSW sample with different depths produced excellent trends of the first-order rate with vertical stress. First Oder Rate Equation (FORE) analysis indicated that the maximum total and dry unit weight of MSW ( and ) achieved at depth in the waste mass were 12.9 kN/m3 and 10.6 kN/m3, respectively. Based on the waste shrinkage ratio (WSR) defined as the initial dry unit weight divided by succeeding dry unit weight, the height of the original MSW pile was estimated to be 40.5 m. Different compression parameters, including aggregated MSW compression index (Cc), modified compression index (CCE), and compression ratio parameter (Cc’), were comparably evaluated, which can be beneficial to understand compressibility and settlement processes in a landfill. Implications: Geotechnical properties and biological status of undisturbed municipal solid waste (MSW) associated with depth were analyzed by using a large-diameter borehole sampling method. The wet and dry unit weights of the MSW sample with different depths produced excellent trends of the first-order rate with vertical stress. Based on the waste shrinkage ratio (WSR) defined as the initial dry unit weight divided by succeeding dry unit weight, the height of the original MSW pile was estimated to be 40.5 m. Different compression parameters, including aggregated MSW compression index (Cc), modified compression index (CCE), and compression ratio parameter (Cc’), were comparably evaluated, which can be beneficial to understand compressibility and settlement processes in a landfill.

This paper describes the results of a study into the undrained response of clay specimens reinforced with sand-coir fiber cores in triaxial tests. Coir, used to reinforce sand, is the processed fiber from the husk of coconuts. Coir combines the properties of biodegradability and fiber strength, and remains an under-utilized material of great potential value for ground improvement in parts of the world where such materials are available in abundance. A thin PVC pipe kept centrally inside a split mold is used to form the core in the triaxial tests. The clay is placed inside the mold around the PVC pipe at maximum dry unit weight—optimum moisture content condition while the sand-coir mixture is placed inside the pipe at the same bulk unit weight as that of clay. Influence of variables such as replacement area ratio (ratio of cross-sectional area of sand-coir fiber core to that of the triaxial test specimen), confining pressure, fiber content, and fiber aspect ratio on the behavior of the composite soil specimen is identified and isolated. It is found that stress-strain strength properties of clay specimens reinforced with sand-coir fiber core is appreciably better not only when compared with untreated clay specimens but with sand core reinforced clay specimens as well. Such an improvement is of importance to allow reduced requirement of sand and increased use of natural fiber. An optimum fiber content of 1 % (by weight) was identified for strengthening of the sand core. The reinforcement effect is found to increase appreciably with increase in replacement area ratio and to a smaller extent with increase in fiber aspect ratio. The larger reinforcement effect observed at higher confining pressures suggests that the proposed method is more effective at greater depths.

Standard Proctor compaction tests were carried out to obtain the optimum reference mix containing fly ash + 8% lime + 0.9% gypsum. The result of light compaction study reveal that addition of small percentage of gypsum (less than 1%) to the fly ash + 8% lime mix has no effect on the dry unit weight and optimum moisture content. The reference mix so obtained was mixed with randomly distributed dry/wet tire chips to study the unconfined compressive strength, energy absorption capacity and cracking pattern of the specimen by varying the tire chip content (5% to 15%), curing period (7 days to 180 days) and curing methods. The results of this study indicated that unconfined compressive strength, energy absorption capacity and cracking pattern of the reference mix containing dry/wet tire chips is influenced by the tire chip content, curing period and curing method. The study further reveals that the unconfined compressive strength and energy absorption capacity of specimen can be increased using wet tire chips in comparison to dry tire chip in the reference mix. Study on unit weight reveals that it decreases with the increase in tire chip content in the reference mix. Further the specimens containing 5% dry/wet tire chip content were observed to fail by development of multiple cracking where as specimen with higher percentage (15%) of dry/wet tire chips results in zig-zag cracking behavior of the specimen. The reference mix with wet tire chips can be a good material for road sub base having light traffic and disposal of these materials will be in an environmental friendly manner.

Support vector machine-based prediction of unconfined compressive strength of Multi-Walled Carbon nanotube doped soil-fly ash mixes