Cavity Expansion Analysis Research Articles

Evaluation of self-penetration potential of a bio-inspired site characterization probe by cavity expansion analysis

Site investigations at limited-access project sites often require mobilization of smaller rigs that may not have the reaction mass required to perform soundings to the desired depth. This study explores the feasibility of a new conceptual bio-inspired solution by adapting functional principles from organisms whose primary mode of locomotion is soil burrowing, including razor clams, caecilians, and earthworms. These organisms radially expand a segment of their body to increase the normal radial pressure acting on it to temporarily form an anchor. This study evaluates the dimensions required for self-penetration of an idealized bio-inspired probe consisting of a radially expanding shaft and a penetrating tip. Cavity expansion analyses, field test data, and theoretical relationships from the literature are used to evaluate the self-penetration potential in different soil types. The results indicate that the resistance to self-penetration is higher in dense sands than in silts and clays. In sands, the resistance to self-penetration is greater for sands that exhibit a more dilative behavior at a given overburden pressure. On the contrary, the resistance to self-penetration in clays decreases slightly as the overconsolidation ratio is increased. The relative dimensions required to initiate self-penetration predicted by cavity expansion analysis are compared with the dimensions of various burrowing organisms.

Analysis of cylindrical cavity expansion in anisotropic critical state soils under drained conditions

This paper presents a semi-analytical solution for the drained cylindrical cavity expansion problem using the well-known anisotropic modified Cam clay model proposed by Dafalias in 1987. The prominent feature of this elastoplastic model, i.e., its capability to describe both the initial fabric anisotropy and stress-induced anisotropy of soils, makes the anisotropic elastoplastic solution derived herein for the cavity problem a more realistic one. Following the development by Chen and Abousleiman in 2013 of a novel solution scheme that establishes a link between the Eulerian and Lagrangian formulations of the condition of radial equilibrium, the plastic zone solution can eventually be obtained by solving a system of eight partial differential equations with the three stress components, three anisotropic hardening parameters, specific volume, and preconsolidation pressure being the basic unknowns. Parametric studies have been conducted to explore the influences of K0 consolidation anisotropy and overconsolidation ratio (OCR), and their pronounced impacts on the stress patterns outside the cavity as well as on the development of stress-induced anisotropy are clearly observed.

Analysis of dynamic spherical cavity expansion in undrained modified Cam Clay soil

SummaryIn order to capture the influence of the cavity expansion velocity, this paper presents a semianalytical solution for dynamic spherical cavity expansion in modified Cam Clay (MCC) soil. The key problem is solving the six coupled partial differential equations (PDEs) of cavity expansion, in which the dynamic term is considered in the stress equilibrium equation. The similarity transformation technique is used to transform the PDEs into ordinary differential equations (ODEs). Subsequently, the numerical method using the function “ODE45” in MATLAB is selected to solve the ODEs, which allows the stress and excess pore pressure around the expanding spherical cavity wall to be obtained. The proposed semianalytical solution for dynamic spherical cavity expansion was validated by comparting the degenerate solution with the published quasistatic solution for the MCC model. Parametric study was then conducted to capture the influence of the cavity wall velocity on the cavity expansion response. The proposed solution has potential application to geotechnical problems such as dynamic pile driving, the dynamic cone penetration test, and so forth.

Two‐dimensional elastoplastic analysis of cylindrical cavity problems in Tresca materials

SummaryThis paper presents analytical elastic‐plastic solutions for static stress loading analysis and quasi‐static expansion analysis of a cylindrical cavity in Tresca materials, considering biaxial far‐field stresses and shear stresses along the inner cavity wall. The two‐dimensional static stress solution is obtained by assuming that the plastic zone is statically determinate and using the complex variable theory in the elastic analysis. A rigorous conformal mapping function is constructed, which predicts that the elastic‐plastic boundary is in an elliptic shape under biaxial in situ stresses, and the range of the plastic zone extends with increasing internal shear stresses. The major axis of the elliptical elastic‐plastic boundary coincides with the direction of the maximum far‐field compression stress. Furthermore, considering the internal shear stresses, an analytical large‐strain displacement solution is derived for continuous cavity expansion analysis in a hydrostatic initial stress filed. Based on the derived analytical stress and displacement solutions, the influence of the internal shear stresses on the quasi‐static cavity expansion process is studied. It is shown that additional shear stresses could reduce the required normal expansion pressure to a certain degree, which partly explains the great reduction of the axial soil resistance due to rotations in rotating cone penetration tests. In addition, through additionally considering the potential influences of biaxial in situ stresses and shear stresses generated around the borehole during drillings, an improved cavity expansion approach for estimating the maximum allowable mud pressure of horizontal directional drillings (HDDs) in undrained clays is proposed and validated.

Penetration resistance of hybrid-fiber-reinforced high-strength concrete under projectile multi-impact

In this paper, the penetration resistance potential of hybrid-fiber-reinforced high-strength concrete (HFRHSC) is investigated at fiber content of 2%. 12 batches of HFRHSC materials with various hybridizations were manufactured for comparative analyses of hybridization. The uniaxial compression tests were conducted to determine the 7-day and 28-day compressive strength indicating that the steel fiber outperforms the polypropylene fiber and polyvinyl alcohol fiber in improving compressive strength. The sequent multi-impact penetration tests for each mixture HFRHSC target were carried out with projectile impact locations in equilateral triangle shape whereas the penetration response was evaluated in terms of depth of penetration (DOP) and crater area. The experimental results indicate that the penetration resistance improvement potential of steel fiber reinforced concrete goes moderately ahead of that of the polypropylene or polyvinyl alcohol fiber reinforced concrete. Besides, the DOP caused by multi-impact implies the penetration resistance is remarkably decayed by the first impact while the second penetration poses much less deterioration. Moreover, cavity expansion analysis together with impact damage were applied to the DOP analytical model for HFRHSC multi-impact penetration whereby the target resistance term corresponding each impact was achieved via best fitting. The accumulated damage is also found to be dependent on the hybridization.

Influence of fiber mixture on impact response of ultra-high-performance hybrid fiber reinforced cementitious composite

The penetration resistance potential of ultra-high-performance hybrid fiber reinforced cementitious composite (UHP-HFRCC) was investigated at fiber content of 2 %. Plain cementitious composite (PCC) versus 12 groups of UHP-HFRCC materials with various fiber mixtures were adopted herein for comparative analyses. The uniaxial compression tests were conducted to determine the 7-d and 28-d compressive strength indicating that the steel fiber outperforms the polypropylene fiber and polyvinyl alcohol fiber in improving compressive strength. The subsequent penetration tests for each mixture UHP-HFRCC target were performed and the penetration resistant performance was evaluated in terms of depth of penetration (DOP) and crater area. The experimental results suggested that the penetration resistance improvement potential of steel fiber reinforced cementitious composite goes moderately ahead of that of the polypropylene fibers or polyvinyl alcohol fibers cementitious composite. For the UHP-HFRCC targets, the steel fiber proportion increase generally resulted in the reduction of DOP and crater area. Besides, the hybrid batch target with 3 kinds of fibers might exhibit greater penetration resistant performance compared to the steel fiber hybrid mixture with polypropylene or polyvinyl alcohol fiber. Cavity expansion analysis was applied to develop the DOP analytical model for UHP-HFRCC penetration whereby the target resistance parameter was best fitted. Finally, the fiber hybrid reinforcement effect of UHP-HFRCC on the penetration resistance was evaluated via the hybrid effect index. The combination of steel fiber and polypropylene fiber leads to a positive effect against penetration while the incorporation of steel fiber and polyvinyl alcohol fiber to cementitious composite generally poses a negative effect.

Assessment of Rate Effects in Piezocone Tests from Poroelastic Cavity Expansion Analysis

Assessment of Rate Effects in Piezocone Tests from Poroelastic Cavity Expansion Analysis

Drained analyses of cylindrical cavity expansion in sand incorporating a bounding-surface model with state-dependent dilatancy

• Governing differential equations of the cylindrical cavity expansion problem are solved as an initial value problem . • Rigorous definitions of the invariant stresses permit the examination of the effect of k 0 value. • Model parameters that are of paramount importance for the cylindrical cavity expansion analyses are presented. This paper presents a semi-analytical drained solution for cylindrical cavity expansion in sand. By introducing an auxiliary variable, defined as the ratio of the original position to the current position of a material particle, the governing differential equations of the cylindrical cavity expansion problem can be transformed into a group of first-order ordinary differential equations. These equations are solved as an initial value problem by incorporating a bounding-surface model with state-dependent dilatancy. This approach does not require the division of the material around the cavity into an elastic zone and a plastic zone. The state-dependent dilatancy model employed in this study allows the investigation of the effects of the initial relative density and mean normal stress of the sand, whereas the rigorous definitions of the invariant stresses permit the examination of the effect of the initial ratio of the horizontal stress to the vertical stress. Moreover, the model parameters that are of paramount importance for the cylindrical cavity expansion analyses are determined via comprehensive parametric studies.

Upper and lower bound solutions for pressure-controlled cylindrical and spherical cavity expansion in semi-infinite soil

Previous cavity expansion analyses are all performed in infinite soil. However, cavity expansion problem in half space (or semi-infinite soil) is also required in geotechnical engineering (tunneling and compaction grouting). New upper and lower bound solutions are derived for expanded spherical and cylindrical cavities in half space of Tresca soil based on the method of finite element limit analysis in this paper. Two types of case, namely homogenous soil and non-homogenous soil with undrained strength linearly increased with depth, are consider in the analysis. Simple empirical closed-form equations are then proposed for predicting the limit cavity expansion pressure through nonlinear regression analysis. The present solutions provide theoretical reference for the corresponding geotechnical engineering problems such as tunneling and compaction grouting.

Drained cavity expansion analysis with a unified state parameter model for clay and sand

This paper presents an analytical solution for drained expansion in both spherical and cylindrical cavities with a unified state parameter model for clay and sand (CASM). The solution developed here provides the stress and strain fields during the expansion of a cavity from an initial to an arbitrary final radius. Small strains are assumed for the elastic region and large strains are applied to soil in the plastic region by using logarithmic strain definitions. Since its development, the unified CASM model has been demonstrated by many researchers to be able to capture the overall soil behaviour for both clay and sand under both drained and undrained loading conditions. In this study, the CASM model is used to model soil behaviour whilst a drained cavity expansion solution is developed with the aid of an auxiliary variable. This is an extension of the undrained solution presented by the authors in 2017. The parametric study investigates the effects of various model constants including the stress-state coefficient and the spacing ratio on soil stress paths and cavity expansion curves. Both London clay and Ticino sand are modelled under various initial stress conditions and initial state parameters. The newly developed analytical solution highlights the potential applications in geotechnical practice (e.g., for the interpretation of cone penetration test data) and also provides useful benchmarks for numerical simulations of cavity expansion problems in critical state soils.

Numerical study on the hard projectile perforation on RC panels with LDPM

This paper numerically investigates the medium-caliber hard projectile perforation of steel rebar reinforced concrete panels by using the recently developed Lattice Discrete Particles Model (LDPM). With mesoscale constitutive laws governing cohesive fracture, strain hardening in compression and compaction due to pore collapse, LDPM naturally captures the failure mechanisms at the length scale of coarse aggregate of concrete. A constant area and shape partition method for circular cross-section is employed to determine the Gauss integration points distribution for beam elements. The sliding friction model for rebar-concrete interaction, in conjunction with LDPM for concrete are utilized for RC panel perforation modeling. Simulations of normal and high strength concrete panel perforation tests are carried out to validate the numerical model whereby agreement with the experimental data is achieved in terms of projectile residual velocity as well as damage contour. Extensive simulations are further performed to investigate the effect of projectile impact location and reinforcement on high strength concrete (HSC) panel perforation responses. Comparative numerical studies indicate that the projectile residual velocity is significantly reduced when the projectile hits the reinforced rebars. Furthermore, the reinforcement can considerably limit the damage area, crack openings and prevent the concrete shelter from structural failure. Finally, the LDPM simulations of HSC panel perforation are combined with cavity expansion analysis to achieve the RC perforation analytical model whereas the target resistance parameter R (Forrestal et al., 2003) is determined a672 MPa while the shear plugging thickness value is estimated as 33 mm for the cases of interest.

Size-dependent finite strain analysis of cavity expansion in frictional materials

This paper presents unified solutions for elastic–plastic expansion analysis of a cylindrical or spherical cavity in an infinite medium, adopting a flow theory of strain gradient plasticity. Previous cavity expansion analyses incorporating strain gradient effects have mostly focused on explaining the strain localization phenomenon and/or size effects during infinitesimal expansions. This paper is however concerned with the size-dependent behaviour of a cavity during finite quasi-static expansions. To account for the non-local influence of underlying microstructures to the macroscopic behaviour of granular materials, the conventional Mohr–Coulomb yield criterion is modified by including a second-order strain gradient. Thus the quasi-static cavity expansion problem is converted into a second-order ordinary differential equation system. In the continuous cavity expansion analysis, the resulting governing equations are solved numerically with Cauchy boundary conditions by simple iterations. Furthermore, a simplified method without iterations is proposed for calculating the size-dependent limit pressure of a cavity expanding to a given final radius. By neglecting the elastic strain increments in the plastic zone, approximate analytical size-dependent solutions are also derived. It is shown that the strain gradient effect mainly concentrates in a close vicinity of the inner cavity. Evident size-strengthening effects associated with the sand particle size and the cavity radius in the localized deformation zone is captured by the newly developed solutions presented in this paper. The strain gradient effect will vanish when the intrinsic material length is negligible compared to the instantaneous cavity size, and then the conventional elastic perfectly-plastic solutions can be recovered exactly. The present solutions can provide a theoretical method for modeling the size effect that is often observed in small-sized sand-structure interaction problems.

Dynamic spherical cavity expansion analysis of concrete using the Bingham liquid constitutive model

High pressure exists in concrete targets during hypervelocity penetration. An incompressible concrete material under large deformation can be represented by a liquid constitutive model. The present work modifies the cavity expansion theory by characterizing incompressibility using the Bingham liquid constitutive model, in which the viscosity of an incompressible material is considered according to Cleja-Tigoiu's work. An analytic expression is derived for the relationship between the pressure on a cavity boundary and the velocity of cavity expansion. Then, the effects of material parameters in the modified model are studied, which is the basis of the calculation of the drag force in hypervelocity penetration. The viscosity coefficient (μ0) is the most sensitive parameter for the radial stress on the cavity surface. As μ0 increases, the dimensionless stress on the cavity surface (S) increases and the quadratic relation between S and the velocity of cavity expansion (a˙) becomes weaker. Finally, the penetration depths of long rod hypervelocity penetration into a concrete target are predicted based on the modified model, the results are in good agreement with experimental results.

Undrained cavity expansion analysis with a unified state parameter model for clay and sand

This paper presents a new analytical solution for undrained expansion of spherical and cylindrical cavities in soils with a unified state parameter model for clay and sand (CASM). Large strain and effective stress solutions are derived for soils in the elastic, plastic and critical-state regions. The key advantage of using the state parameter model CASM is that it can model both clay and sand and is generally able to capture overall soil behaviour as observed in the laboratory. The newly developed solution provides the stress and strain fields during the expansion of a cavity from an initial to a final radius. Following the validation with the original Cam Clay solution, a simple parametric study is conducted to investigate the effects of key model parameters on stress distributions and cavity expansion curves. Applications to the analysis of pile installation and self-boring pressuremeter tests highlight some important implications in geotechnical practice.

Analytical and experimental study of high-velocity impact on ceramic/nanocomposite targets

In this paper, an analytical model has been developed for modeling high-velocity impact on ceramic/nanocomposite targets. In this model, the penetration resistance of the ceramic is determined based on the cavity expansion analysis. Also semi-angle of the ceramic conoid is modified. For modeling the back-up composite laminate, the kinetic and strain energy of yarns and shear plugging have been determined. Also the effect of nano-zirconia particles dispersed in the matrix of back-up composite, based on the ballistic performance of the ceramic/nanocomposite target, is investigated. Ballistic impact tests were performed to validate analytical predictions. Experimental results revealed an improvement in the ballistic performance of samples with nano-zirconia particles. The analytical predictions of ballistic limit velocity and residual velocity of projectile are found to be in good agreement with the experimental results.

Cavity Expansion Analysis to Predict Side Shear Set-Up in Clayey Soils

In this study, fifty driven piles located in the Santos Coastal Plain (“Baixada Santista”), Brazil, have been dynamically tested at various times after installation, indicating gain of capacity over time. The average side shear resistance, related to a low-OCR clayey layer – known as SFL soil , was evaluated over time, indicating side shear set-up within a relatively narrow range of values (between 2.0 and 2.5) approximately 20 days after installation. The cavity expansion theory, which considers an ideal cohesive soil, has been used to predict the effective radial stress over time, considering two main parameters: undrained shear strength and horizontal coefficient of consolidation. Finally, the average of measured pile shaft capacities were compared to the unit shear resistances predicted by the Method (effective stress method). The theoretical values of side shear set-up are fairly similar to the results of the analyzed load tests, which seems to support the viability of the presented method.

Theoretical Analysis of Dynamic Spherical Cavity Expansion in Reinforced Concretes

This paper aims to establish a model that considers the penetration resistance caused by the constraint effects of steel reinforcements on concrete. Firstly, based on the experiment phenomena that reinforcements increase the toughness and tensile strength of concretes, the fitting relational expression between toughness of reinforced concrete and ratio of reinforcement was used to improve the Griffith yield criterion for reinforced concrete. Then, the dynamic spherical cavity expansion analysis was developed using the improved Griffith yield criterion as constitutive model and the dilation equation as equation of state, and the response regions were consisted of six distinct zones: cavity, compaction zone, dilation zone, radially cracked zone, elastic zone and undisturbed zone. This dynamic analysis considered the compression and dilation of concretes at the same time and was applicable to the penetration problem of reinforced concrete target. At last, based on the theoretical model of this paper, the experiments of projectiles with different weights penetrating into reinforced concrete targets with different reinforcement ratios were calculated using penetration analysis method of rigid projectiles. The comparison results showed that the theoretical analysis model of this paper can be used to predict the depth of penetration and other physical parameters such as velocity and deceleration with certain rationality.

Interpretation of Cone Penetration Test Data in Layered Soils Using Cavity Expansion Analysis

Cavity expansion theory plays an important role in many geotechnical engineering problems, including the cone penetration test (CPT). One of the challenges of interpreting CPT data is the delineation of interfaces between soil layers and the identification of distinct thin layers, a process which relies on an in-depth understanding of the relationship between penetrometer readings and soil properties. In this paper, analytical cavity expansion solutions in two concentric regions of soil are applied to the interpretation of CPT data, with a specific focus on the layered effects during penetration. The solutions provide a large-strain analysis of cavity expansion in two concentric regions for dilatant elastic-perfectly plastic material. The analysis of CPT data in two-layered soils highlights the effect of respective soil properties (strength, stiffness) on CPT measurements within the influence zones around the two-soil interface. Results show good comparisons with numerical results and elastic solutions. A simple superposition method of the two-layered analytical approach is applied to the analysis of penetration in multilayered soils. A good comparison with field data and numerical results is obtained. It is illustrated that the proposed parameters effectively capture the influence of respective soil properties in the thin-layer analysis. It is also shown that results based on this analysis have better agreement with numerical results compared with elastic solutions.

Analysis of Undrained Cylindrical Cavity Expansion Considering Three-Dimensional Strength of Soils

AbstractUndrained cylindrical cavity-expansion solutions that were based on the modified Cam-clay model have been widely used to predict and interpret geotechnical problems, such as pile installation, and in pressuremeter tests in saturated clay. However, the yield and failure of soils around the cavity might not be properly modeled by the extended Mises criterion adopted in the modified Cam-clay model. To consider the three-dimensional mechanical properties of soils during cavity expansion, an analytical solution with the spatially mobilized plane criterion-based Cam-clay model is derived for the undrained cylindrical cavity-expansion problem by using the stress-transformed method. The presented solution is verified by two well-documented pile-installation tests and is compared with the modified Cam-clay model–based solutions in detail. The results show that the prediction from the presented solution is closer to the actual stress field induced by the undrained cylindrical cavity expansion. However, the ...

A Comment on “Review of Quasi-Analytical and Cavity Expansion Methods for Projectile Penetration of Concrete Targets”, by R. Sobeski and G. Urgessa, Int. J. Protective Structures, 6(1), 43–64 (2015)

The relevance of the cavity expansion analyses to the penetration mechanics of rigid projectiles, impacting metallic and concrete targets, is discussed. In the past six years we offered an alternative approach to that reviewed by Sobeski and Urgessa (2015), and we briefly discuss that work in this comment. To our best understanding, the cavity expansion analyses are irrelevant to the penetration mechanics of rigid projectiles impacting metallic or concrete targets.