Shallow Penetration Research Articles

Characterization of PuO2 With Visible and UV Raman Spectroscopy: Discrimination Between the Bulk, Surface, and an Intermediate Disordered Layer

ABSTRACTRaman spectroscopy is an ideal tool in the characterization of materials including PuO2. The wavelength‐dependent absorptivity of the material defines the light penetration depth and the relative Raman scattering contribution from the bulk and the surface. The surface contribution to the total Raman scattering was investigated for PuO2 calcined at various temperatures and recorded with laser wavelengths of 355, 325, and 244 nm. These experiments provided the first glimpse of the wavelength‐dependent disappearance and emergence of new phonons and electronic bands from the PuO2 surface layers. The first indication of the wavelength transition in the Raman spectra was the loss of the 2LO2 (overtone, ~1155 cm−1) band and the weakening intensity of the Г1 → Γ5 electronic band (~2135 cm−1) with the 355‐nm excitation laser. The Γ5 electronic band was barely visible with the 244‐nm excitation. The electronic band located at ~1050 cm−1, corresponding to the Г1 → Γ4 electronic transition was observed to dramatically increase in intensity while the Г1 → Γ3 electronic band (2640 cm−1) sharpened as the UV wavelength was increased in energy from the near‐ to deep‐UV (355–325–244 nm). The FWHM of the T2g band was found to vary with calcination temperature (450°C and 900°C) with the 325‐nm laser and the 244‐nm laser. The T2g band attributes, the strong emergence of the Г1 → Γ4 electronic band, and the disappearance of the 2LO2 overtone acquired with the 244‐nm excitation for the different calcination temperatures suggest a shallow penetration depth.

Recent advances and design strategies for organic afterglow agents to enhance autofluorescence-free imaging performance.

Long-lasting afterglow luminescence imaging that detects photons slowly being released from chemical defects has emerged, eliminating the need for real-time photoexcitation and enabling autofluorescence-free in vivo imaging with high signal-to-background ratios (SBRs). Organic afterglow nano-systems are notable for their tunability and design versatility. However, challenges such as unsatisfactory afterglow intensity, short emission wavelengths, limited activatable strategies, and shallow tissue penetration depth hinder their widespread biomedical applications and clinical translation. Such contradiction between promising prospects and insufficient properties has spurred researchers' efforts to improve afterglow performance. In this review, we briefly outline the general composition and mechanisms of organic afterglow luminescence, with a focus on design strategies and an in-depth understanding of the structure-property relationship to advance afterglow luminescence imaging. Furthermore, pending issues and future perspectives are discussed.

In Vivo Surface-Enhanced Transmission Raman Spectroscopy and Impact of Frozen Biological Tissues on Lesion Depth Prediction.

Plasmonic surface-enhanced transmission Raman spectroscopy (SETRS) has emerged as a promising optical technique for detecting and predicting the depths of deep-seated lesions in biological tissues. However, in vivo studies using SETRS are scarce and typically show shallow penetration depths. Moreover, the optical parameters used in the prediction process are often derived from frozen samples and there is limited understanding of how freezing affects the optical properties of biological tissues and the accuracy of depth prediction in living models. In this work, we conduct in vivo SETRS measurements on thick abdominal tissue region of the live rats to investigate the impact of freezing on the measured optical properties for the purpose of depth prediction. First, we fabricated ultrahigh bright surface-enhanced Raman spectroscopy (SERS) nanotags and utilized a custom transmission Raman system. We then measured the change of optical attenuation at two different wavelengths (Δμ) for four types of rat tissues (including skin, fat, muscle, and liver) following freezing. The freezing process dramatically affects Δμ values, even after only 1 day of freezing. In contrast, Δμ values obtained from fresh samples enable precise localization of SERS lesion phantoms in the live rat with only 5% deviation. The total thickness of the live rat is 2.6 cm, which, to the best of our knowledge, is the highest value of in vivo SETRS studies so far. This work helps to fill the gap in the SERS field of tissue localization and optical coefficient studies in highly heterogeneous tissues, and demonstrates the potential of the SETRS technique to achieve precise clinical localization of deep lesions.

Beveled microneedles with channel for transdermal injection and sampling, fabricated with minimal steps and standard MEMS technology.

Microneedles hold the potential for enabling shallow skin penetration applications where biomarkers are extracted from the interstitial fluid (ISF) and drugs are injected in a painless and effective manner. To this purpose, needles must have an inner channel. Channeled needles were demonstrated using custom silicon microtechnology, having several needle tip geometries. Nevertheless, all the proposed fabrication sequences are not compatible with mass production based on mature, standard microfabrication techniques. Furthermore, ISF extraction was also demonstrated with channeled needles but under poorly controlled conditions and over long periods of time, the latter being impractical for medical use. A range of factors may impede or slow ISF extraction that require controlled experiments. In this work we address the above tasks in terms of microfabrication sequence design, tip geometry design and experimental validation under controlled conditions. We report the development and fabrication of a silicon channeled microneedle array using conventional, industrial micromechanic processes. With only 2 lithography steps, a hypodermic needle tip profile is achieved. Using the fabricated microneedles, fluid extraction is experimented on chicken skin mockups. Extraction tests are carried out by inducing a controlled pressure gradient between the two ends of the microneedle channels, generated by loading the chip or by applying vacuum to the chip's backside. The extraction of more than 1 μL of fluid in 20 minutes is demonstrated with a maximum applied pressure gradient of 500 mbar. A correlation between the extraction rate efficiency and needles' density is observed, both for short and long extraction times. These results provide the first demonstration of in vitro interstitial fluid collection under controlled experimental conditions using silicon hollow microneedles fabricated with standard micro electro mechanical systems (MEMS) fabrication technology and minimal steps. Based on the obtained data, a comparison is drawn between pressure load and vacuum as drivers for ISF extraction, according to modelling and controlled experiments.

Resistive force modeling for shallow cone penetration into dry and wet granular layers

AbstractEstimating penetration resistive forces on granular materials is important for applications in various research fields. This paper investigates resistive forces into dry and wet granular layers through theoretical analysis and discrete element simulations. Theoretical model is derived from slip line field theory by assuming materials with cohesion and inter-particle friction. This model indicates that penetration resistive forces are composed of the sum of the buoyancy-like force proportional to the penetration volume and the cohesion-derived force proportional to the penetration cross-sectional area. The model is compared with the simulation results of various cones shallowly penetrating into granular layers with/without liquid-bridge forces between particles. For cohesion-derived force, the simulated resistive forces agree with the theoretical model within a factor of two. For buoyancy-like force, on the other hand, the simulated resistive forces deviate from the theoretical model by up to five times as the cone-tip angle increased. To solve the discrepancy, this paper introduces the correction factor depending on the relationship between stagnant zone and cone shape. As a result, a maximum difference between the proposed model and simulated force are reduced to twice. Thereby, it turns out that the proposed model can compute penetration resistive forces on granular layers in a wide range of cone-tip angles and water content conditions.

The Optical Forces and Torques Exerted by Airy Light-Sheet on Magnetic Particles Utilized for Targeted Drug Delivery.

The remarkable properties of magnetic nanostructures have sparked considerable interest within the biomedical domain, owing to their potential for diverse applications. In targeted drug delivery systems, therapeutic molecules can be loaded onto magnetic nanocarriers and precisely guided and released within the body with the assistance of an externally applied magnetic field. However, conventional external magnetic fields generated by permanent magnets or electromagnets are limited by finite magnetic field gradients, shallow penetration depths, and low precision. The novel structured light field known as the Airy light-sheet possesses unique characteristics such as non-diffraction, self-healing, and self-acceleration, which can potentially overcome the limitations of traditional magnetic fields to some extent. While existing studies have primarily focused on the manipulation of dielectric particles by Airy light-sheet, comprehensive analyses exploring the intricate interplay between Airy light-sheet and magnetic nanostructures are currently lacking in the literature, with only preliminary theoretical discussions available. This study systematically explores the mechanical response of magnetic spherical particles under the influence of Airy light-sheet, including radiation forces and spin torques. Furthermore, we provide an in-depth analysis of the effects of particle size, permittivity, permeability, and incident light-sheet parameters on the mechanical effects. Our research findings not only offer new theoretical guidance and practical references for the application of magnetic nanoparticles in biomedicine but also provide valuable insights for the manipulation of other types of micro/nanoparticles using structured light fields.

A novel NIR-activatable and photodegradable mitochondria-targeted nano-photosensitizer for superior photodynamic therapy

Photodynamic therapy (PDT) has garnered significant interest as a promising approach for cancer treatment due to its effectiveness, versatility, and non-invasiveness. However, its clinical application is hindered by several factors, such as suboptimal efficacy, poor targeting capabilities, shallow penetration depth, and safety concerns. Herein, we introduce B-SQ, a novel nano-photosensitizer that addresses these challenges. B-SQ is a self-assembling, cancer mitochondria-targeting agent that is both activatable and photodegradable, designed by strategically modifying a near-infrared fluorescent squaraine dye. We extensively assessed the PDT potential of B-SQ in various cancer cell models and explored the molecular mechanisms of PDT-induced cell death. Importantly, B-SQ demonstrated high specificity for cancer cells, and its PDT efficiency was activatable, with near-infrared fluorescence to distinguish cancer cells from normal cells. This work provides the first evidence of B-SQ inducing the intrinsic mitochondrial apoptosis pathway and cell cycle arresting in cancer cells via PDT. Additionally, its photodegradable nature is likely to minimize side effects after treatment. This research introduces an innovative class of nano-photosensitizers that are activatable, targeting cancer mitochondria, and are photodegradable with near-infrared fluorescence. These qualities present new possibilities for safer and more effective clinical cancer treatments in the future.

Optical penetration depth and periodic motion of a photomechanical strip

Liquid crystal elastomers (LCEs) containing light-sensitive molecules exhibit large, reversible deformations when subjected to illumination. Here, we investigate the role of optical penetration depth on this photomechanical response. We present a model of the photomechanical behavior of photoactive LCE strips under illumination that goes beyond the common assumption of shallow penetration. This model reveals how the optical penetration depth and the consequent photomechanically induced deformation can depend on the concentration of photoactive molecules, their absorption cross-sections, and the intensity of illumination. Through a series of examples, we show that the penetration depth can quantitatively and qualitatively affect the photomechanical response of a strip. Shallow illumination leads to monotone curvature change while deep penetration can lead to non-monotone response with illumination duration. Further, the flapping behavior (a cyclic wave-like motion) of doubly clamped and buckled strips that has been proposed for locomotion can reverse direction with sufficiently large penetration depth. This opens the possibility of creating wireless light-driven photomechanical actuators and swimmers whose direction of motion can be controlled by light intensity and frequency.

An Acceptor-Donor-Acceptor Structured Nano-Aggregate for NIR-Triggered Interventional Photoimmunotherapy of Cervical Cancer.

Compared with conventional therapies, photoimmunotherapy offers precise targeted cancer treatment with minimal damage to healthy tissues and reduced side effects, but its efficacy may be limited by shallow light penetration and the potential for tumor resistance. Here, an acceptor-donor-acceptor (A-D-A)-structured nanoaggregate is developed with dual phototherapy, including photodynamic therapy (PDT) and photothermal therapy (PTT), triggered by single near-infrared (NIR) light. Benefiting from strong intramolecular charge transfer (ICT), the A-D-A-structured nanoaggregates exhibit broad absorption extending to the NIR region and effectively suppressed fluorescence, which enables deep penetration and efficient photothermal conversion (η=67.94%). A suitable HOMO-LUMO distribution facilitates sufficient intersystem crossing (ISC) to convert ground-state oxygen (3O2) to singlet oxygen (1O2) and superoxide anions (·O2 -), and catalyze hydroxyl radical (·OH) generation. The enhanced ICT and ISC effects endow the A-D-A structured nanoaggregates with efficient PTT and PDT for cervical cancer, inducing efficient immunogenic cell death. In combination with clinical aluminum adjuvant gel, a novel photoimmunotherapy strategy for cervical cancer is developed and demonstrated to significantly inhibit primary and metastatic tumors in orthotopic and intraperitoneal metastasis cervical cancer animal models. The noninvasive therapy strategy offers new insights for clinical early-stage and advanced cervical cancer treatment.

Achieving Ultrasound-Excited Emission with Organic Mechanoluminescent Materials.

Unlike traditional photoluminescence (PL), mechanoluminescence (ML) achieved under mechanical excitation demonstrates unique characteristics such as high penetrability, spatial resolution, and signal-to-background ratio (SBR) for bioimaging applications. However, bioimaging with organic mechanoluminescent materials remains challenging because of the shallow penetration depth of ML with short emission wavelengths and the absence of a suitable mechanical force to generate ML in vivo. To resolve these issues, the present paper reports the achievement of ultrasound (US)-excited fluorescence and phosphorescence from purely organic luminogens for the first time with emission wavelengths extending to the red/NIR region, with the penetrability of the US-excited emission being considerably higher than that of PL. Consequently, US-excited subcutaneous phosphorescence imaging can be achieved using a mechanoluminescent-luminogen-based capsule device with a quantified intensity of 9.15 ± 1.32 × 104 p s-1 cm-2 sr-1 and an SBR of 24. Moreover, the US-excited emission can be adequately tuned using the packing modes of the conjugated skeletons, dipole orientation of mechanoluminescent luminogens, and strength and direction of intermolecular interactions. Overall, this study innovatively expands the kind of excitation sources and the emission wavelengths of organic mechanoluminescent materials, paving the way for practical biological applications based on US-excited emission.

NIR-triggered NO production combined with photodynamic therapy for tumor treatment

Photodynamic therapy (PDT), as one of the most promising cancer therapy methods, is still limited by several drawbacks, such as tissue hypoxia and shallow light penetration of blue-violet light (200–450 nm), and red light (750 nm) is more penetrating to tissues than blue-violet light, but still lower than near-red light (750–1350 nm). Therefore, we proposed a synergistic therapy system by combining the near-infrared light-triggered PDT with nitric oxide (NO)-based gas therapy to enhance the anti-tumor effects. Upconversion nanoparticles (UCNPs) were loaded with the photosensitizers of ZnPc and the NO donors of l-arginine (L-Arg) to obtain the nanocomposites of UCN@mSiO2@ZnPc@L-Arg. Under 980 nm laser irradiation, reactive oxygen species (ROS) could be produced for PDT and react with l-Arg to produce NO, which is previously reported to have a greater killing effect on tumor cells than ROS and also plays an important role in promoting PDT in our study. Both the in vitro and in vivo tests demonstrated that the combined therapy of PDT with NO therapy could enhance the tumor killing effect significantly compared with the unique application of PDT. The UCNPs-based nanocomposites are expected to be widely used in biomedicine for tumor inhibition.

Shallow penetration conformance sealants (SPCS) based on organically cross-linked polymer and particle gels—An overview

Shallow penetration conformance sealants (SPCS) based on organically cross-linked polymer and particle gels—An overview

Dissecting Exciton Dynamics in pH‐Activatable Long‐Wavelength Photosensitizers for Traceable Photodynamic Therapy

AbstractTumor‐specific activatable long‐wavelength (LW) photosensitizers (PSs) show promise in overcoming the limitations of traditional photodynamic therapy (PDT), such as systemic phototoxicity and shallow tissue penetration. However, their insufficient LW light absorption and low singlet oxygen quantum yield (Φ 1O2) usually require high laser power density to produce thermal energy and synergistically enhance PDT. The strong photothermal radiation causing acute pain significantly reduces patient compliance and hinders the broader clinical application of LW PDT. Through the exciton dynamics dissection strategy, we have developed a series of pH‐activatable cyanine‐based LW PSs (LET‐R, R = H, Cl, Br, I), among which the activated LET‐I exhibits strong light absorption at 808 nm and a remarkable 3.2‐fold enhancement in Φ 1O2 compared to indocyanine green. Transient spectroscopic analysis and theoretical calculations confirmed its significantly promoted intersystem crossing and simultaneously enhanced LW fluorescence emission characteristics. These features enable the activatable fluorescence and photoacoustic dual‐modal imaging‐escorted complete photodynamic eradication of tumors by the folic acid (FA)‐modified LET‐I probe (LET‐I‐FA), under the ultralow 808 nm laser power density (0.2 W cm−2) for irradiation, without the need for photothermal energy synergy. This research presents a novel strategy of dissecting exciton dynamics to screen activatable LW PSs for traceable PDT.

Energy-Dispersive X-Ray Microanalysis – as a Method for Study the Aluminium-Polysilicon Interface after Exposure with Long-Term and Rapid Thermal Annealing

Energy dispersive X-ray microanalysis is one of the main methods for determining the elemental composition of matter. Possessing high locality and a relatively shallow penetration depth of the electron beam (< 1 μm), this method has found wide application in the field of microelectronics, as the main method for analyzing the elemental composition of matter. The method allows to study the surface of a substance both pointwise and over an area with the construction of element distribution maps. In the paper we investigated the influence of long-term and rapid heat treatments on the formation of the aluminum-polysilicon interface in order to study the formation of ohmic contacts in the element base of integrated circuits. The aluminumpolysilicon interface was studied using energy-dispersive X-ray microanalysis. It has been established that during long-term thermal annealing (450 °C, 20 min) polysilicon is completely dissolved in aluminum followed by its segregation in the form of separate agglomerates in the aluminum film, which can lead to a complete failure of the integrated circuit. During rapid thermal annealing (450 °C, 7 s) such a phenomenon was not detected. Thus it is advisable to use rapid thermal annealing as an alternative to traditional long-term thermal annealing in microelectronics. This makes it possible to significantly reduce the dissolution of polysilicon in aluminum, avoid the destruction of ohmic contacts and increase the percentage of yield of workable 0products in the process of integrated circuits' manufacturing.

Dual-modal fiber-optic sensor for simultaneous pH and temperature monitoring in tumor microenvironment

The tumor microenvironment (TME) is a complex system. Temperature, pH, oxygen content, and other biomarkers comprehensively reflect the growth state of the tumor, necessitating a multi-parameter detection strategy to garner the precise status of tumor for treatment guidance. Fluorescence imaging technology is a promising tool for realizing this goal due to its advantages of low cost, real-time responses, and high sensitivity. However, several limitations, including the shallow penetration depth of fluorescence signals in biological tissues and the potential crosstalk between multiple fluorescence signals, hinder the practical application of current fluorescence imaging technology. In this paper, a dual-mode optical fiber sensor consisting of a fiber fluorescence pH sensor and a fiber Bragg grating (FBG) temperature sensor is presented. The compact sensor uses different principles for pH and temperature monitoring, thus effectively eliminating potential crosstalk between different signals. In addition, its small size allows it to be inserted into deep tissues for detection. The sensor responds quickly to changes in pH.Moreover, the temperature sensitivity of FBG packaged with PDMS is 34 % higher than the uncoated FBG. In vivo experiments confirmed that the sensor can accurately distinguish normal tissues and tumor tissues. The proposed sensor provides a novel way to realize multi-parameter monitoring of tumor microenvironment and improve the specificity of tumor detection.

Estimating relative density from shallow depth CPTs in normally consolidated and overconsolidated siliceous sand

Current interpretation of relative density (<i>D<sub>r</sub></i>) based on CPT end resistance (<i>q<sub>c</sub></i>) data in sand relies on empirical expressions established from calibration chamber studies for which a deep failure penetration mechanism is attained. These expressions are mainly based on stress normalised <i>q<sub>c</sub></i> data. Previous studies have highlighted the importance of performing the normalisation procedure with respect to the mean effective stress (<i>p'</i>) in overconsolidated (OC) sand deposits instead of the vertical effective stress (<i>σ'<sub>v</sub></i>) that has been used in normally consolidated (NC) deposits. Due to a large variation in the coefficient of earth pressure at rest (<i>K<sub>0</sub></i>), on which <i>p'</i> depends, in the uppermost (3-5) m of OC sand, a recent study has demonstrated a rigorous unified approach for estimating a varying <i>K<sub>0</sub></i> with depth. However, the surficial shallow failure penetration effects are not accounted for, and consequently, interpretation of the upper (0.5-1.5) m of sand is still erroneous. This depth range is very important for low stress geotechnical applications such as offshore flowlines and mudmats. With a reinterpretation of previously published data, a new global model is presented that enables estimation of <i>D<sub>r</sub></i> from shallow CPTs in siliceous sand by taking into account both the shallow failure penetration effects (important in the uppermost 0.5-1.5 m) as well as the varying <i>K<sub>0</sub></i> with depth for OC sand (important in the uppermost 3-5 m).

Relationships among soil moisture at various depths under diverse climate, land cover and soil texture

Soil moisture is an important component of the hydrological cycle and a key mediator between land surface and atmospheric interactions. Although substantial progress has been made in remote sensing of soil moisture at different spatial scales, the shallow penetration depth of remote sensors greatly limits their utility for applications in meteorological modelling and hydrological studies where the critical variable of interest is the root-zone soil moisture content. Therefore, this study assesses the relationship between soil moisture at the surface (10 cm) and in lower soil layers (20, 40, 60, 80, 100, and 120 cm) under varying climates, soils, and crop types. Cross-correlation analysis is applied to daily in-situ soil moisture measurements from 4712 locations in agricultural lands across the contiguous United States. Our analysis demonstrates that zero-day lag always produced the highest correlation between 10 cm soil moisture and soil moisture in the lower layers. In addition, a positive and strong relationship between 10 and 20 cm soil moisture (r = 0.84) was observed, while the relationships between 10 and 40 cm soil moisture were moderate (r = 0.52). The decline in cross-correlation continued to the deeper soil layers, which indicated that, on a daily timescale, the surface soil moisture gradually becomes decoupled with soil moisture at greater depths. Therefore, our research suggests that the estimation of soil moisture in the soil layers up to 40 cm based on surface soil moisture is most promising. However, the influence of climate, crop type, and soil texture on the strength of relationships between surface and lower layers makes the prediction difficult. The comparatively weak relationship between precipitation and soil moisture (0.09–0.32), as well as the relationship between reference evapotranspiration (ETo) and soil moisture (−0.19–0.18), in this study can be attributed to scale mismatching from different data sources.

Hyaluronic acid modified indocyanine green nanoparticles: a novel targeted strategy for NIR-II fluorescence lymphatic imaging.

The lymphatic system, alongside blood circulation, is crucial for maintaining bodily equilibrium and immune surveillance. Despite its importance, lymphatic imaging techniques lag behind those for blood circulation. Fluorescence imaging, particularly in the near-infrared-II (NIR-II) region, offers promising capabilities with centimeter-scale tissue penetration and micron-scale spatial resolution, sparking interest in visualizing the lymphatic system. Although indocyanine green (ICG) has been approved by the Food and Drug Administration (FDA) for use as a near-infrared-I (NIR-I) region fluorescent dye, its limitations include shallow penetration depth and low signal-to-noise ratio. Research suggests that ICG's fluorescence emission tail in the second near-infrared window holds potential for high-quality NIR-II imaging. However, challenges like short circulation half-life and concentration-dependent aggregation hinder its wider application. Here we developed HA@ICG nanoparticles (NPs), a superior ICG-based NIR-II fluorescent probe with excellent biocompatibility, prolonging in vivo imaging, and enhancing photostability compared to ICG alone. Leveraging LYVE-1, a prominent lymphatic endothelial cell receptor that binds specifically to hyaluronic acid (HA), our nanoprobes exhibit exceptional performance in targeting lymphatic system imaging. Moreover, our findings demonstrate the capability of HA@ICG NPs for capillary imaging, offering a means to assess local microcirculatory blood supply. These compelling results underscore the promising potential of HA@ICG NPs for achieving high-resolution bioimaging of nanomedicines in the NIR-II window.

Boundary effect on the soil strength estimation from T-bar penetration tests

The T-bar penetration tests have gained widespread use in assessing the undrained shear strength of marine clays. However, when dealing with model tests or sampled soil with a small diameter of the tube, the reliability of T-bar test results is influenced by both the boundary effect and the soil flow mechanism around the T-bar. In this paper, a comprehensive investigation into the boundary effect on T-bar penetration resistance was conducted by using the large deformation finite element (LDFE) method in conjunction with laboratory tests. The study reveals that the boundary conditions significantly impact the T-bar resistance when the lateral boundary dimension is smaller than 12D. Specifically, the T-bar penetration resistance is underestimated for smooth boundaries and overestimated for rough boundaries. For soils with higher strength, a larger boundary size is required. The bottom boundary also affects the T-bar resistance until the full-flow mechanism is established. However, once the full-flow mechanism is achieved, the boundary effect on T-bar penetration resistance diminishes, even for small lateral boundary sizes (2D). Considering the fact that it is challenging to attain the full-flow mechanism, especially for higher strength soils, a simple algorithm is proposed to estimate soil strength based on a shallow penetration depth (2D). This algorithm is validated through laboratory tests. To address the difficulty in achieving the full-flow mechanism, by applying the overburden pressure during the T-bar test, a novel T-bar test method is suggested. This innovative approach promises to resolve the issue effectively.

Effect of soil stiffness on end bearing resistance of foundations in clay from large deformation numerical modelling

Accurately predicting the installation resistance is of great benefit to a rational and economical design of foundations. This research performs a large-deformation finite-element analysis to investigate the effect of soil stiffness on the end bearing resistance in uniform clay. Different types of geotechnical structures and foundations, e.g., cone penetrometer, strip foundation, bucket foundation, and deep piled foundation are considered. Results show that soil stiffness has a negligible impact during shallow penetration but becomes pronounced at deep penetration. It is found that for strip footings, effect of soil stiffness is minimal, whereas the end bearing resistances of CPT and deep piled foundation with a partial plug are highly dependent on the soil stiffness. For a rough pile foundation, the resistance factor Nc,pf increases by approximately 30% as soil rigidity Ir increases from 50 to 500. For a bucket foundation, the effect of soil stiffness on the end bearing resistance falls between that of “shallow” and “deep” foundations. Based on the numerical results, empirical expressions are proposed to predict the end bearing resistance factor accounting for the effect of soil stiffness.