Unit Weight Of Soil Research Articles

Innovative Approach for the Determination of Unit Weight and Density of Soil and Rock Masses

Innovative Approach for the Determination of Unit Weight and Density of Soil and Rock Masses

Investigation of relationship between cone penetration test and unit weight in cohesive soil (Study case: Gunung Anyar District)

Cone Penetration Test or CPT is one of soil investigation which is used to determine the mechanical properties of soil i.e., cone resistance and sleeve friction. Since several decades ago, CPT is often used as a common thread to determine the physical properties of soil such as soil unit weight of soil, soil behaviour type, etc. Thus, empirical approaches have been developed from various countries. However, these empirical approaches are not the same as the condition in Indonesia. Therefore, it is necessary to obtain and develop the suitable correlation for the type of cohesive soil. In this study, primary and secondary data were carried out from Gunung Anyar area. From statical analysis result, the regression shows less than 60% similarity of the model. In addition, the result of this study found that silt and clay soil types were found to dominate in Gunung Anyar area.

Comparative Study in Method of Compaction by Consolidated Drained and Direct Shear Test

Soil compaction has been a common practice in the construction of highways, embankments, earth dams and other related structures where the condition of the soil is high in void ratio and therefore having a very low in bearing capacity. Therefore, the soil needs to be compacted in order to minimize the void ratio and in the same time would results in having a very high bearing capacity to sustain load. Nevertheless, only a few researches have been done to investigate the method of compaction using different energy on the behavior of shear strength by consolidated drained and direct shear test. In this research, the effect of different compaction in energy of 25 number of blows compared to 40 number of blows on the stress-strain behaviour of drained triaxial test has been done and findings of the data are to be compared with direct shear test. Results reveal that there is an increase in soil unit weight by using different energy in compaction with an increase of 5% from 1790 kg/m3 to 1880 kg/m3 for 25 and 40 number of blows respectively. However, the stress-strain behaviour of the specimens shows differently when compared between consolidated drained triaxial and direct shear test. The shear strength for direct shear-stress is at higher value compared to drained triaxial test. For drained triaxial test, results reveal that the effective friction angles are increase only about 1% from 37° to 38°. This is due to the soil particles rearranging itself with the different applied pressures thus eliminating the effects of different energy on the shear strength of the specimens. However, for direct shear test, the shear strength increases drastically from 29° to 32°. The increase of the shear strength is more likely influence by the soil particle arrangement due to the impact of the energy of the no of blows to the desired specimen.

Uplift and lateral buckling failure mechanisms of offshore pipes buried in normally consolidated clay

Buried offshore pipelines are crucial for the swift transportation of oils and similar fluidized materials from the oil rigs to the processing center or vice versa. In this study, a 2-D finite element analysis is performed to understand the pipeline-soil interaction, the failure mechanism of soil and the variation of capacity factors with different normalised soil properties during upward and lateral buckling of a buried offshore pipeline for no tension (NT) and full tension (FT) condition. The pipeline is installed in a normally consolidated clay bed with linearly varying undrained shear strength. The effect of embedment depth (H), unit weight of soil (γ'), undrained shear strength (Su), and roughness and tensile capacity of the pipe-soil interface on the failure mechanism and capacity factors of pipes are also studied. The current numerical model is validated first against a past numerical study, which showed a good agreement between the result obtained from the current study and the results obtained from the past study (Maitra et al., 2016). Then the failure mechanism and capacity factors are obtained, and their variation for different combinations of embedment depth and unit weight of soil are demonstrated. Both the uplift and lateral capacity factors are observed to be influenced by embedment depth and unit weight of soil. It is observed that, depending on the influencing parameters, both the uplift and lateral capacity factors can be critical for the buckling of the pipeline. Several displacement diagrams are presented to show the failure mechanisms clearly, while, the stress contours are given to observe the behavior of principal effective stresses during different failure mechanisms.

Assessment of Liquefaction Potential of Barhadashi Municipality, Jhapa District, Nepal

This paper evaluates the liquefaction potential of Barhadashi which is a small rural municipality of Jhapa district, Nepal. Mogami and Kubo (1953) first coined the term liquefaction. This paper follows R.W. Boulanger & I.M. Idriss (2014) which is SPT and CPT based procedures. Liquefaction occurs in saturated soils or partially saturated soils during earthquake or when it is subjected to stresses such as ground motion like underground mining, transportation, nuclear detonation, heavy machine vibration and so on. Major factors that affect the liquefaction are unit weight of soil, penetration test values, depth of water table, percentage of fines content and peak ground acceleration. Some of these factors have influence on each other and change in one factor brings the change in other factors too. Considering the sparsely populated and small area of Barhadashi three boreholes were drilled to obtain the SPT-N value and soil sample for laboratory testing. This paper analyses liquefaction for earthquake of magnitude 8.0 and compares CRR8.0 with CRR6.0. Liquefaction susceptibility and potential were determined at all three sites and it was found all three sites were susceptible to liquefaction up to depth 6.0m for earthquake of magnitude of 8.0.

Estimation of lateritic soils elastic modulus from CBR index for pavement engineering in Burkina Faso

Pavement design with some soils, such as lateritic soils, is still a “real challenge” in some countries. In the tropical countries guide, recommended for Burkina Faso, the pavement design is performed according to the class of traffic and the soil bearing capacity, characterized by the soaked CBR index (Californian Bearing Ratio). In practice, the validation of pavement structures is possible using numerical models requiring the thickness, the Poisson’s ratio and the elastic modulus of the pavement’s layer materials, as input data for the stresses and the strain calculation. Until now, the guides provide none value of the modulus for the lateritic soils. So, the modulus is estimated by assimilating the lateritic soils to untreated coarse gravels (or GNT: Graves Non Traitees in the French guideline) with known modulus or by using empirical correlations based on the soaked CBR index. This approach lead to an erroneous estimating of modulus of lateritic soils, and to an under or overdesign of pavement structures, due to the fact that the specific correlation suitable for these soils in Burkina Faso is not known. So, this paper was interested in the characterization of lateritic soils from Burkina Faso, according to their CBR bearing capacity, their elastic modulus and to their compaction parameters, after having been assured that the selected soils were representative of country’s road soils. The objective is to perform a specific model for estimating the elastic modulus of these soils. Analysis of the studied parameters showed that CBR and elastic modulus, both depend on moisture content and dry unit weight of soils. A correlation was thus performed between elastic modulus and CBR index. The specific correlation obtained is in power form: E= a.CBRb and relatively close to whose obtained by Green and Hall, where a=66.50 and b=0.526.

Seismic Bearing Capacity of Strip Foundations on Fiber-Reinforced Granular Soil

The present study investigated the bearing capacity of strip footings on a bed of granular fiber-reinforced soils. Analyses were performed by the stress characteristics method (SCM). The failure criterion considers anisotropic distribution of fiber orientation and ignores the rupture of reinforcements. Seismic effects were included in the stress equilibrium equations as the horizontal and vertical pseudo-static coefficients. Stress equilibrium equations were solved by the finite difference method. A computer code was provided to solve the problem. Using the soil and reinforcement input parameters, the code determines the characteristics network and calculates the bearing capacity. The bearing capacity was expressed as the bearing capacity factors of the soil unit weight and surcharge. Parametric analysis was performed to investigate the effect of soil and reinforcement parameters on the bearing capacity and the shape of the failure zone. The outcomes indicated that the SCM results lower ultimate bearing capacity as compared with the upper bound method. Also, the depth of the failure zone increases with an increase in the amount of reinforcement or decrease in the horizontal seismic coefficient. Considering the anisotropic distribution of fiber orientations leads to more bearing capacity than the isotropic distribution.

Eco-Friendly Design of Reinforced Concrete Retaining Walls: Multi-objective Optimization with Harmony Search Applications

In this study, considering the eco-friendly design necessities of reinforced concrete structures, the acquirement of minimizing both the cost and the CO2 emission of the reinforced concrete retaining walls in conjunction with ensuring stability conditions has been investigated using harmony search algorithm. Optimization analyses were conducted with the use of two different objective functions to discover the contribution rate of variants to the cost and CO2 emission individually. Besides this, the integrated relationship of cost and CO2 emission was also identified by multi-objective analysis in order to identify an eco-friendly and cost-effective design. The height of the stem and the width of the foundation were treated as design variables. Several optimization cases were fictionalized in relation with the change of the depth of excavation, the amount of the surcharge applied at the top of the wall system at the backfill side, the unit weight of the backfill soil, the costs, and CO2 emission amounts of both the concrete and the reinforcement bars. Consequently, the results of the optimization analyses were arranged to discover the possibility of supplying an eco-friendly design of retaining walls with the minimization of both cost and gas emission depending upon the comparison of outcomes of the identified objective functions. The proposed approach is effective to find both economic and ecological results according to hand calculations and flower pollination algorithm.

Effect of Edge Distance on Lateral Capacity of Piles in Cohesionless Soil Slopes

Recent advances in the understanding of deep foundation mechanisms suggest that the pile foundations can be used in both level grounds and the sloping grounds to appropriately support the heavy axial and lateral loads coming from the superstructures. The lateral load-carrying capacity of the pile in the sloping ground is different from the level ground due to the presence of slope and pile location (i.e., edge distance). In this study, extensive numerical analyses were performed to understand the behavior of a laterally loaded pile in cohesionless soil slopes by using the three-dimensional finite element method. Effect of various influencing parameters like slope inclination, relative density, angle of internal friction, modulus of elasticity of soil, unit weight of soil, L/D ratio of a pile, and pile diameter on the laterally loaded pile with a change in edge distance was studied. Results from the numerical analyses were compared with the previous experimental studies. An attempt has also been made to find out critical edge distance (i.e., where the effect of slope angle is negligible on lateral capacity) of the pile for different cohesionless soils with varying slope configurations. The critical edge distance is found to be varying between 5.0–7.5D, 7.5–10.0D, and 10.0–15.0D with slope inclinations of 20°, 30°, and 40°, respectively.

Monte carlo simulation for stability of finite slope subjected to earthquake loading

Analysis of finite slopes is a common practical problem which faces the geotechnical engineering. The aim of the slope analysis is to predict the safety factor against shear failure of the slope which is the ratio between the resisting and the disturbing forces developed along an assumed slip surface. Presence of seismic forces due earthquake lead to more critical situation. The deterministic approaches are employed for this purpose. These approaches do not take into account the uncertainty related to soil properties and/or seismic loads in their procedures. In the present work, a probabilistic approach is adopted using the Monte Carlo simulation technique to study the effect of uncertainty due to soil properties (unit weight, angle of internal friction and cohesion) and seismic accelerations (vertical and horizontal). The results of the work demonstrate that the use of probabilistic approach will yield more accurate results for estimating the safety factor and then economic design of the slope. Also, the results reveal that the statistical properties for the soil shear strength parameters have significant impact on the standard deviation of the output (factor of safety), while the soil unit weight and horizontal acceleration have small effect. However, the vertical acceleration has no effect on it. On other hand, the mean of the output distribution does not affect by the statistical parameters of all input variables. All cases simulated in this study give reliability index (RI) less than 3. Hence, RI values indicate that there are unsatisfactory level of safety for the slope subjected to seismic loading. Finally, the soil shear strength parameters have the same positive significant impact on the safety factor. But, the soil properties and the coefficient of the horizontal acceleration should be selected carefully in the stability analysis due to the effect of their uncertainty on the analysis results.

Influence of Energy on Compaction Characteristics of High Expansive Soils

Each soil type has different behavior with regard to determination of maximum dry density and optimum moisture content and therefore any soil type has its own compaction requirements for experimental purposes and for control the compaction in the field. The general purpose of this study is to a better understanding of the compaction characteristics of high expansive soils, with emphasis on the relationships of moisture content and dry density of high expansive soils at a range of compaction energy levels. To achieve this purpose, high expansive soils samples were subjected to Atterberg limit and a set of laboratory compaction tests to find compaction characteristics namely; maximum dry unit weight and optimum water content of high expansive soils at different compaction energy (compaction effort) for different number of hammer blows per each layer range from 10 to 50, which varied the energy per unit volume from 356 KN/m3 to 1188 KN/m3.Rather than single peak compaction curves, the most achieved compaction curves are an irregular one and half peak compaction curves. According to the comparison results of different compaction energy, it was concluded that the maximum dry unit weight of high expansive soil was not highly affected by gradually increase of applied energy. The results showed that, the maximum dry density of tested expansive soils sample increased from 1.48g/cm3 to 1.6g/cm3 with increase of compaction energy from 356 KN/m3 to 1188 KN/m3.

Face stability of shallow tunnelling in sandy soil considering unsupported length

This paper proposes a three-dimensional log-spiral prism model considering unsupported length to analyse the face stability of shallowly buried tunnels in sandy soil based on the limit equilibrium method. The limit support pressures and collapse zones obtained from the proposed model are validated by the results of numerical simulation, model tests and existing collapse models. The parametric analysis results show that the limit support pressure appears linear relationships to the soil unit weight, cohesion and surface surcharge, and increases significantly with the increases of the tunnel diameter and aspect ratio. The cover depth ratio has little effect on the limit support pressure when the cover depth ratio exceeds 2.0. The extent of the collapse zone decreases noticeably with the increase of the internal friction angle. The log-spiral slip surface turns steeper and the collapse zone above the tunnel extends behind the tunnel face as the unsupported length increases. The proposed model is of good accuracy and efficiency, and has more extensive applicability in face stability analysis of practical shallowly buried tunnels.

Optimal Design of Cantilever Soldier Pile Retaining Walls Embedded in Frictional Soils with Harmony Search Algorithm

In this paper, the design of cantilever soldier pile retaining walls embedded in frictional soils is investigated within the insight of an optimization algorithm to acquire cost and dimension equilibrium by ensuring both geotechnical and structural requirements simultaneously. Multivariate parametric analyses with different fictionalized cases are performed to evaluate the effects of design variants and to compare the effectiveness of the preference of optimization solutions rather than detailed advanced modeling software. The harmony search algorithm is used to conduct parametrical analyses to take into consideration the effects of the change of excavation depth, shear strength angle, and unit weight of soil, external loading condition, and coefficient of soil reaction. The embedment depth and diameter of the soldier pile are searched as design dimensions, and the total cost of a cantilever soldier pile wall is calculated as an objective function. The design dimension results of the parametric optimization analysis are used to perform finite element analysis with a well-known commercial geotechnical analysis software. The results of optimization and finite element solutions are compared with the use of maximum bending moment, factor of safety, and pivot point location values. As the consequence of the study, the influence rates of design variants are procured, and the effectiveness of the usage of optimization algorithms for both cost and dimensional equilibrium is presented.

Failure Modes of Laterally Loaded Piles Under Combined Horizontal Load and Moment Considering Overburden Stress Factors

A large number of studies on various aspects of laterally loaded piles in clay have been conducted in the literature based on experimental and numerical analyses; however, the lack of studies on the influence of the soil unit weight on the undrained capacity of the problem is obvious. In this paper, the effects of the overburden stress factors on the undrained capacity of laterally loaded piles under combined horizontal load and moment are comprehensively investigated by employing the three-dimensional (3D) finite element analysis. In the present study, soil–pile interfaces are modelled as the no-tension condition while the influences of the pile length ratios are also examined in the numerical analyses. The failure envelopes of laterally loaded piles under combined horizontal load and moment incorporating overburden stress factors, pile length ratios are presented. Employing the normality rule to the derived failure envelopes, the failure mechanisms corresponding to the ratio between applied moment and horizontal load are postulated in this paper. An approximate solution of the failure envelope of laterally loaded piles is also proposed by using a nonlinear regression analysis, and provides a convenient tool for predicting the undrained lateral capacity of piles considering overburden stress factors in practice.

Estimating the Unit Weight of Local Organic Soils from Laboratory Tests Using Artificial Neural Networks

The estimation of the unit weight of soil is carried out using laboratory methods; however, it requires high-quality research material in the form of samples with undisturbed structures, the acquisition of which, especially in the case of organic soils, is extremely difficult, time-consuming and expensive. This paper presents a proposal to use artificial neural networks to estimate the unit weight of local organic soils as leading parameters in the process of checking the load capacity of subsoil, under a direct foundation in drained conditions, in accordance with current standards guidelines. The initial recognition of the subsoil, and the locating of organic soils at the Theological and Pastoral Institute in Rzeszow, was carried out using a mechanical cone penetration test (CPTM), using various interpretation criteria, and then, material for laboratory tests was obtained. The analysis of the usefulness of the artificial intelligence method, in this case, was based on data from laboratory tests. Standard multi-layer backpropagation networks were used to predict the soil unit weight based on two leading variables: the organic content LOIT and the natural water content w. The applied neural model provided reliable prediction results, comparable to the standard regression methods.

Sensitivity Analysis of Factors Affecting Stability of Cut and Fill Multistage Slope Based on Improved Grey Incidence Model

There are many factors affecting the stability of cut and fill multistage slopes, and these factors exert different degrees of influence on slope stability. The grey incidence analysis method can be used to evaluate the sensitivity of these factors. To overcome the shortcomings of the grey incidence analysis model used in previous sensitivity analysis studies on the factors influencing slope stability, this study improved the dimensionless processing method and resolution coefficient value. Considering that the importance of each influencing factor is different, the vector resemblance degree theory was applied to determine the weight of each influencing factor. Finally, based on an actual cut and fill multistage slope, the sensitivity of the factors affecting stability was analyzed according to the improved grey incidence analysis theory. The results revealed that the unloading platform width, cohesion force, and internal friction angle are most sensitive to the stability of the cut and fill multistage slope. The step height, slope width, and slope height are slightly sensitive, while the soil unit weight, seismic peak acceleration, and slope ratio are the least sensitive.

Ultimate bearing capacity of strip footing on sands under inclined loading based on improved radial movement optimization

Improved radial movement optimization (IRMO) is adopted to investigate the critical slip surface and ultimate bearing capacity of a rough embedded strip footing on sands under inclined loading using the upper-bound limit analysis. Based on the Mohr–Coulomb yield criterion, a planar kinematically admissible multi-block failure mechanism of strip footing under inclined loading is formulated. The soil is assumed to be elastic–perfectly plastic material with an associated flow rule, and a solution procedure for the ultimate bearing capacity is established based on the virtual work principle. The results show that IRMO can calculate the ultimate bearing capacities efficiently, accurately and stably. The size and shape of normalized failure envelopes and inclination factors depend on the friction angle and embedment ratio. Moreover, the errors of the joint and individual influences of soil unit weight and surcharge for the bearing capacity of strip footing decrease with increasing load inclination angle α.

New approach for face stability assessment of tunnels driven in nonuniform soils

Abstract A novel approach to assess the face stability of a plane strain tunnel driven in nonuniform soils is proposed herein. The failure mechanism of a tunnel face is established by a discretization-based approach within the framework of the limit analysis method. It is generated point by point and the vertical length of each element is fixed, which is beneficial for addressing stability problems involving depth-dependent soil parameters. The cohesion, internal friction angle, and unit weight of soils are modelled as varying with depth, which is closer to the true characteristics of the soils. First, the proposed approach is degraded to a conventional upper bound analysis by considering a uniform soil case to validate the proposed approach. A practical problem concerning longitudinal weak strata positioned ahead of the tunnel face is investigated using the presented approach. To highlight the effects on the critical support pressure and failure domain of the tunnel face, the thicknesses, positions, and soil parameters of weak strata are further discussed. Finally, numerical simulations are performed to demonstrate the accuracy of the proposed approach in the face stability assessment of tunnels affected by weak strata.

Support pressure for circular tunnels advanced below water bodies

The limiting support pressure required to be exerted by a support system for maintaining stability of circular tunnel driven in granular soils below water bodies has been computed. The analysis was performed on the basis of lower bound theorem of plasticity in conjunction with finite elements and second order cone programming. The effect of anisotropy in both strength and hydraulic properties of granular soil on the magnitude of required support pressure has been examined. The required support pressure is defined in terms of non-dimensional factors normalized with respect to unit weight of soil and diameter of tunnel. The variation of support pressure for different combinations of strength and hydraulic properties of soil, height of water level above bed of water body, and diameter and cover of tunnel has been established. The magnitude of support pressure is observed to be substantially influenced by strength anisotropy of soil; whereas, the influence of hydraulic anisotropy is shown to be insignificant on the support pressure. Moreover, the support pressure is found to be increasing with increase in the height of water level and is found to be higher in the case of tunnel driven below water bodies than that advanced in dry soil.

Support pressure for circular tunnels in two layered undrained clay

Abstract To estimate the required support pressure for stability of circular tunnels in two layered clay under undrained condition, numerical solutions are developed by performing finite element lower bound limit analysis in conjunction with second-order cone programming. The support system is assumed to offer uniform internal compressive pressure on its periphery. From the literature, it is known that the stability of tunnels depends on the overburden pressure acting over it, which is a function of undrained cohesion and unit weight of soil, and cover of soil. When a tunnel is constructed in layered undrained clay, the stability depends on the undrained shear strength, unit weight, and thickness of one layer relative to the other layer. In the present study, the solutions are presented in a form of dimensionless charts which can be used for design of tunnel support systems for different combinations of ratios of unit weight and undrained shear strength of upper layer to those of lower layer, thickness of both layers, and total soil cover depth.