This paper describes a computational framework for the numerical analysis of quasi-static soil-structure insertion problems in water saturated media. The Particle Finite Element Method is used to ...solve the linear momentum and mass balance equations at large strains. Solid-fluid interaction is described by a simplified Biot formulation using pore pressure and skeleton displacements as basic field variables. The robustness and accuracy of the proposal is numerically demonstrated presenting results from two benchmark examples. The first one addresses the consolidation of a circular footing on a poroelastic soil. The second one is a parametric analysis of the cone penetration test (CPTu) in a material described by a Cam-clay hyperelastic model, in which the influence of permeability and contact roughness on test results is assessed.
Microbially induced calcite precipitation (MICP) is a potentially environmentally conscious ground improvement method that can improve the engineering properties of granular soils through the ...precipitation of calcite. In this study, an experiment involving two 1.7 m diameter tank specimens was completed to investigate the effect of bio-cementation on cone penetrometer and geophysical measurements in sands. Following nonuniform bio-cementation treatments, specimens achieved calcite contents ranging from 0.5% to 5.3% by mass, shear wave velocity (V
s
) values between 131 and 967 m/s, and mid-depth cone penetration resistances (q
c
) ranging between 3.6 and 32.1 MPa. At calcite contents exceeding 5.0%, q
c
and V
s
improvements were as high as 527% and 686%, respectively. Although cone penetration resistance, sleeve friction, and friction ratio measurements exhibited limited sensitivity to bio-cementation at calcite contents of less than 3.0%, V
s
measurements successfully detected bio-cementation at calcite contents near 1.0%. When q
c
and V
s
measurements were compared at similar locations, increases in an empirical parameter (K
G
) enabled improved detection of bio-cementation at calcite contents near 0.5%. Large increases in normalized tip resistances (Q
tn
) and small decreases in normalized friction ratios (F
r
) with increasing bio-cementation resulted in cemented materials plotting near and within the gravelly sand and sand-like dilative soil behavioral type regions using two soil behavior type (SBT) charts.
Shear wave velocity, V
s
, is a soil mechanical property that can be advantageously measured in both the field and laboratory under real and controlled conditions. The measured V
s
values are ...customarily used in conjunction with other in situ (e.g., standard penetration test blow count, N-SPT, and cone penetration resistance, q
c
-CPT) and laboratory (e.g., effective confining pressure,
σ
m
′
, and void ratio, e) measurements to establish an abundant number of V
s
-based correlations that could later be utilized to augment (in some cases, replace) designated testing. An attempt is made here to present the salient features of some existing widely used correlations to provide the reader with a comprehensive understanding about the nature of these correlations and their applicability in geotechnical engineering practices. It is recognized that the reliability of some of these empirical formulations, still in general use today, has been questioned, as they are characterized by their lack of dependence on stress state and particle characteristics. A new V
s1
–(N
1
)
60
(where V
s1
is the stress-normalized shear wave velocity, and (N
1
)
60
is the stress-normalized penetration blow count) correlation that accounts for grain sizes is highlighted by combining a recently published V
s1
–q
c1
(where q
c1
is the stress-normalized cone tip resistance) formulation and available (N
1
)
60
–q
c1
relationships. The new formulation is applicable to uncemented relatively young Holocene-age soil deposits. The estimated V
s1
values based on the proposed correlation are compared with reliable laboratory and field measurements, and the comparison shows that accounting for grain size of granular soils yields more realistic results regarding the V
s
values than when particle size is not considered. The prime effect of grain size was to change the range of possible void ratios, which in turn had a substantial impact on V
s
values. Moreover, a new V
s1
–(N
1
)
60
chart has been proposed, allowing the practitioner to estimate V
s1
values based on a combination of data including N-SPT, e, grain size, and relative density.
Abstract
For the new marine Ti6321 titanium alloy, the penetration tests were carried out under vertical and oblique penetration conditions. The ballistic properties of Ti6321 titanium alloy with ...different structures and the macro and micro damage characteristics of the target were obtained. The influence of the structure on the ballistic performance and failure mechanism of the titanium alloy target plate was analyzed. The results show that Ti6321 titanium alloy exhibits different properties under vertical and oblique penetration conditions. In the vertical penetration test, the absolute penetration depth and the average crater diameter of the equiaxed target plate are smaller than those of the bimodal and Widmanstatten structure, which show a better resistance to vertical penetration. In the oblique penetration, the safety angle of the bimodal structure was smaller and showed better resistance to the oblique penetration.
Aiming to improve the density of calcium hexaaluminate (CA6), Zr4+ doped CA6 with the structural formula of CaAl11.73◊0.25Zr0.02O18.41◊0.59 (CaAl11.73Zr0.02O18.41) was successfully synthesized at ...1600℃ for 4 h in air. The effect of Zr4+ doping on the crystal structure of CA6 was investigated using first principle calculation, structure refinement in combination with experimental characterization. The results suggest that Zr4+ prefers to substitute the Al3+ at Al3 site, which can increase the lattice parameter of c‐axis and the amount of Al vacancies. The average thickness of Zr4+ doped CA6 is increased by approximate 36% in comparison with the pure one. In addition, molecular dynamics (MD) simulation indicates that Zr4+ doping can reduce the wettability of CA6 to slag to some extent. The reaction test method was carried out and it shows that CA6 with Zr4+ doping possesses better slag penetration resistance. Based on this, the reaction mechanism is also discussed.
This paper presents a novel perspective to understanding the spatial and statistical patterns of a cone penetration dataset and identifying soil stratification using these patterns. Both local ...consistency in physical space (i.e., along depth) and statistical similarity in feature space (i.e., logQ
t
–logF
r
space, where Q
t
is the normalized tip resistance and F
r
is the normalized friction ratio, or the Robertson chart) between data points are considered simultaneously. The proposed approach, in essence, consists of two parts: (i) a pattern detection approach using the Bayesian inferential framework and (ii) a pattern interpretation protocol using the Robertson chart. The first part is the mathematical core of the proposed approach, which infers both spatial pattern in physical space and statistical pattern in feature space from the input dataset; the second part converts the abstract patterns into intuitive spatial configurations of multiple soil layers having different soil behavior types. The advantages of the proposed approach include probabilistic soil classification and identification of soil stratification in an automatic and fully unsupervised manner. The proposed approach has been implemented in MATLAB R2015b and Python 3.6, and tested using various datasets including both synthetic and real-world cone penetration test soundings. The results show that the proposed approach can accurately and automatically detect soil layers with quantified uncertainty and reasonable computational cost.
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Remarkable advances in nano delivery systems have provided new hope for tumor prevention, diagnosis and treatment. However, only limited clinical therapeutic effects against solid ...tumors were achieved. One of the main reasons is the presence of abundant physiological and pathological barriers in vivo that impair tumoral penetration and distribution of the nanodrugs. These barriers are related to the components of tumor microenvironment (TME) including abnormal tumor vasculature, rich composition of the extracellular matrix (ECM), and abundant stroma cells. Herein, we review the advanced strategies of TME remodeling to overcome these biological obstacles against nanodrug delivery. This review aims to offer a perspective guideline for the implementation of promising approaches to facilitate intratumoral permeation of nanodrugs through alleviation of biological barriers. At the same time, we analyze the advantages and disadvantages of the corresponding methods and put forward possible directions for the future researches.
•The impact experiments of projectile and concrete target have been conducted for impact velocities in range of 500 m/s to 1700 m/s covering three penetration regimes. Parameters of the residual ...projectiles and damage of targets were obtained with large range of impact velocities.•A deforming model has been proposed to investigate the deformable process of projectiles based on the observation of the residual projectiles and penetration depths.•The applicability of existing eroding penetration models penetration into concrete were validated and discussed based on the experimental results.•The eroding penetration process was further discussed by taking the deforming penetration regime into consideration. Influence of projectile and target strength on penetration process were investigated based on the theoretical model.
To have a better understanding of behaviors of projectiles and concrete targets during impacts at different velocities, experiments and analysis of medium carbon steel long-rod projectiles impact on concrete targets have been carried out in this paper. The impact mechanics of projectiles and concrete targets has been investigated for impact velocities in range of 500 m/s to 1700 m/s covering three penetration regimes. Based on the observation of the residual projectiles and penetration depths, a deforming model has been proposed to investigate the deformable process of projectiles. Furthermore, deforming penetration model was established based on a rigid penetration model and the projectile deformation parameters, which was validated by the experimental results. The applicability of existing eroding penetration models penetration into concrete were validated and discussed based on the experimental results. At last, the eroding penetration model was further justified and improved by taking the deforming penetration regime into consideration. Influence of projectile and target strength on penetration process were investigated based on the theoretical model. Results show that the crater diameter and depth are linearly proportional to the impact velocity, while the volume of the crater and the initial impact kinetic energy of the projectile have a linear relationship. The calculated diameters of residual projectiles and Depth of Penetration (DOP) with a board range of impact velocities are in good agreement with experimental results. It is noted that the strength of projectiles and concrete targets have significantly influences on DOPs and critical velocities.
This paper develops Bayesian approaches for underground soil stratum identification and soil classification using cone penetration tests (CPTs). The uncertainty in the CPT-based soil classification ...using the Robertson chart is modeled explicitly in the Bayesian approaches, and the probability that the soil belongs to one of the nine soil types in the Robertson chart based on a set of CPT data is formulated using the maximum entropy principle. The proposed Bayesian approaches contain two major components: a Bayesian model class selection approach to identify the most probable number of underground soil layers and a Bayesian system identification approach to simultaneously estimate the most probable layer thicknesses and classify the soil types. Equations are derived for the Bayesian approaches, and the proposed approaches are illustrated using a real-life CPT performed at the National Geotechnical Experimentation Site (NGES) at Texas A&M University, USA. It has been shown that the proposed approaches properly identify the underground soil stratification and classify the soil type of each layer. In addition, as the number of model classes increases, the Bayesian model class selection approach identifies the soil layers progressively, starting from the statistically most significant boundary and gradually zooming into less significant ones with improved resolution. Furthermore, it is found that the evolution of the identified soil strata as the model class increases provides additional valuable information for assisting in the interpretation of CPT data in a rational and transparent manner.
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