Dynamic Penetration Research Articles

Discrete-element based simulation of CPT and SPT on a volcanic sand

In situ soil characterization often involves penetration tests. The response to both static and dynamic penetration in volcanic sands is known to be controlled by particle crushing, obscuring the effect of density and confinement on the response. This severely limits the use of penetration tests for soil characterization. In this work a virtual calibration chamber (VCC) built using the discrete element method (DEM) is employed to explore the relationship between cone penetration tests CPTs (static) and standard penetration tests SPTs (dynamic) results on a volcanic sand. The simulated CPT results are shown to capture well experiments from the literature over a range of density and confining stress. The comparison between the simulated CPT and SPT results shows good agreement with empirical expressions based on particle size. It was found that energy-based equivalent dynamic tip resistance obtained from the SPT is a good match for static cone tip resistance if shaft resistance effects are discounted. The results presented confirm the potential of DEM based VCC to examine the performance of in-situ tests in complex soil conditions.

Surface strengthening mechanism of graphene-oxide membrane and its modified aluminium lamina under penetration loading

The contact surface is crucial in determining the ability of membranes or laminas to absorb energy during penetration. This study conducted experiments to explore the mechanical properties of the pristine graphene oxide (GO) membrane when dry, as well as the anti-penetration performance of four surface-modified GO membranes (dry, oil, water, and grease) under various loading velocities. Dynamic penetration occurs when the kinetic energy exceeds a specific threshold, as opposed to the quasi-static outcomes. Additionally, the examination of failure mode indicated that the GO membrane demonstrates significant elastic rebound when subjected to comparatively lower levels of dynamic loading. Further analysis after penetration revealed a transition from brittleness to ductility under dynamic loading conditions. Uniaxial tensile tests of aluminium sheets revealed a distinct negative velocity sensitivity behaviour. Moreover, surface treatment with the GO membrane can enhance the penetration failure strength and energy absorption capacity of the sheet. This study provides crucial insights into the physical principles governing the energy absorption of membrane structures and how they are influenced by surface conditions.

Thickness Estimation of the Soil‐Sedimentary Cover Inside Causewayed Enclosures to Locate an Occupation Layer: Map of the Archaeological Potential of the Neolithic Causewayed Enclosure of Le Pontet

ABSTRACTThe western centre of France is one of the richest regions of Western Europe in terms of causewayed enclosures from the Neolithic period. To date, more than 300 such sites have been identified. Most causewayed enclosures in the region range in size from some hectares to over 10 ha. Exhaustive excavation of such sites is rarely performed because such operations are both financially expensive and time intensive. Completing an exhaustive excavation of these sites is also extremely complicated due to their complexity. Recording the most complete possible site plan is a major challenge for optimizing excavation. Traditionally, aerial photography has been the primary method used for delineating causewayed enclosure plans. A magnetic survey can also provide complementary information. Magnetic imaging reveals both enclosure ditches and internal features (pits, postholes, etc.) quickly and with high spatial resolution. At some sites, occupation layers dating from the time of enclosure may be preserved and contain archaeological artefacts or small features in situ. This article proposes a protocol for locating a Neolithic occupation layer inside a Neolithic causewayed enclosure. To locate the areas where this layer is likely to be present, a map of the archaeological potential of the Le Pontet site was produced based on a thickness map of the soil‐sedimentary cover. This map was created by combining an apparent electrical resistivity map, the results of electrical resistivity tomography, an orthophotograph with contrasting cropmarks and the results of dynamic cone penetration tests. To validate the archaeological potential map, an excavation campaign was conducted in 2020 to investigate several sectors; the aim was to prove the presence of the occupation layer and study the pedo‐sedimentary stratigraphy of the site.

Amino-functionalized rare earth hexanuclear cluster based MOFs for CO2/CH4 separation

Climate pollution and global warming caused by greenhouse gases have become one of our toughest environmental challenges. CO2 capture and separation from natural gas can effectively reduce CO2 emissions and improve energy efficiency, accordingly, it is a serious challenge faced by industrial separation and scientific research to effectively reduce the carbon dioxide concentration in natural gas pipeline transportation and achieve the acquisition of high-purity methane (>99.5 %). In this study, three stable hexanuclear microporous rare earth cluster-based MOFs (Sm-BDC-NH2, Er-BDC-NH2, Y-BDC-NH2) were successfully synthesized. The selectivity of CO2/CH4 was improved by the introduction of amino groups to achieve better CO2/CH4 separation performance, which was proved by dynamic penetration experiments.

Study on the Adsorption of Trace Water in N-Methyl-pyrrolidone Solvents by A-Type Molecular Sieves.

N-Methyl-pyrrolidone (NMP) is an important coating solvent for the production of lithium batteries, and its water content will greatly affect the coating quality and energy density of lithium batteries, which needs to be reduced to 200 ppm. The current vacuum distillation technology suffers from high operating costs and high energy consumption, whereas the pervaporation technology only achieves solvent dehydration up to 99.5%. Therefore, it is of great significance to carry out the study of trace water removal from NMP solvents. In this paper, the A-type molecular sieve adsorption method was used to remove trace water from the NMP solvent, and the effects of molecular sieve type, particle size, adsorption temperature, feeding amount, and contact time on the dehydration performance of NMP system were first investigated. Adsorbed at 25 °C for 240 min at a feeding amount of 120 g/L, 3A molecular sieves were able to reduce the water content of the NMP solvent from 5000 to 140 ppm. Second, Langmuir and Freundlich equations were used to fit the static isothermal adsorption data, and the results showed a better correlation of the Langmuir equation. Then, the adsorption kinetics and diffusion mechanism were analyzed by the kinetic model and the Crank single-pore diffusion model. The R2 of the pseudo-first-order kinetic model was 0.9993, which was more suitable for describing the process of adsorption of water from the NMP solvent by 3A molecular sieves, and the effective diffusion coefficient De = 2.986 × 10-8 cm2/s was calculated for the Crank single-pore adsorption model, which proved water molecules on the 3A molecular sieve. The diffusion of water molecules on the inner surface of the pores is the controlling step of the adsorption process. Finally, the fixed-bed dynamic penetration curves were investigated to obtain the experimental data of fixed-bed adsorption, and the experimental data were fitted using the Thomas and Yoon-Nelson models, which showed that both models could describe the adsorption behavior of trace water in NMP solvents on 3A molecular sieves. This study provides a new idea for the removal of trace water in NMP systems, and a series of model fitting parameters provide basic data for industrial scale-up.

Analysis of influencing factors of penetration mechanism and vertical bearing characteristics of monopile in calcareous sand: Laboratory model testing and in-situ testing

The construction of islands and reef engineering structures in marine environments has been a hot topic in recent years, and calcareous sand, which possesses unique physical properties, is widely distributed on islands and reefs. Due to the properties of calcareous sand, engineering problems such as pile slipping while driving and a low bearing capacity during service can occur. To address the key problem of pile‒soil interactions in calcareous sand foundations, laboratory model and in situ tests were conducted, accounting for factors such as impact energy, relative density, pile-forming method, and pile aspect ratio. First, the penetration mechanism of hammered piles in calcareous sand was studied. Then, the differences in vertical bearing characteristics between hammered and pre-embedded piles under different conditions were explored. The pile driving test results showed that a higher impact energy and lower relative density are more conducive to pile sinking. Moreover, as the number of hammer drops and dynamic penetration resistance increase with increasing burial depth, the pile tip resistance is the main factor limiting pile penetration in calcareous sand. The vertical static loading test revealed that particle breakage accelerates soil redistribution around the pile and that compaction enhances the bearing capacity of the pile. The pile aspect ratio, relative density and pile-forming method also play major roles in the vertical bearing capacity of piles in calcareous sand. In addition, the skin friction of a pile rapidly increases to the ultimate value along a multisegment trend of polyline functions. Similarly, the pile tip resistance rapidly increases at the initial loading stage, exhibiting the behavior of an end-bearing pile. The in situ test results indicated that the pile penetration depth in coral calcareous sand is an important factor affecting the bearing capacity.

Dynamic penetration prediction based on continuous video learning

Dynamic penetration prediction based on continuous video learning

Prediction of Soil Expansivity with Direct and Indirect Method in Banten Region, Indonesia

Expansive soils are widespread in Indonesia, particularly in Banten Province, causing extensive road damages. The study aimed to predict the soil expansivity of soil subgrade along the damaged road segments in Malingping, Cikeusik-Cibaliung, and Labuan districts. Indirect and direct expansivity predictions were employed to determine soil swelling potential. Indirect expansivity prediction was conducted based on various criteria using the Atterberg limit and grain size distribution. Direct expansivity prediction was conducted using an oedometer apparatus to measure the expansion index according to ASTM D-4829. A dynamic cone penetration test was also conducted to measure CBR values. Various indirect methods showed inconclusive results of swelling potentials, low to very high. The direct method provided more conclusive results, Expansivity Index = 100-167 and swelling values = 9%-18%, thus, categorized as expansive clay (high to very high swelling potential). CBR values were 1.49%-5% which is lower than minimum provisioned CBR (6%).

Feature analysis of precipitation-induced subgrade defects on a high-speed rail ballasted track using multiple track inspection data: A case study

Heavy rainfall has posed a great challenge to the service performance of high-speed rail (HSR) substructure, resulting in a reduction in the ride quality and safety of high-speed trains. To carry out proper repair work for the substructure, it is imperative to realize efficient identification of precipitation-induced subgrade defects. To this end, this paper aims to extract the features of typical precipitation-induced subgrade defects from the multiple track inspection data to provide a basis for defect identification. Firstly, the geotechnical site investigation including Ground Penetrating Radar (GPR) detection, moisture content test, and dynamic cone penetration (DCP) test of a typical defective spot is performed to determine the condition of the subgrade after heavy rainfall; then, the analysis methods of track inspection data are introduced; finally, the track geometry data and carbody acceleration data of four typical defective sections are analyzed, and the time-domain, frequency-domain and discrete wavelet transform (DWT)-based features which are highly correlated with the precipitation-induced subgrade defects are extracted. The results show that the feature indexes extracted from track surface irregularity and carbody vertical acceleration increase significantly after heavy rainfall; the long wavelength components (8 m and above) of both track irregularity and carbody vibration are more sensitive to the subgrade defects, which is reflected by the sharp increase of the DWT-based features at some levels corresponding to long wavelength ranges. The results of defect feature extraction based on the track inspection data agree well with the geotechnical site investigation results, which demonstrate the feasibility of utilizing multiple track inspection data to identify the typical precipitation-induced subgrade defects.

Effect of hybrid strategies on the ballistic response of aramid/ultra-high molecular weight polyethylene woven fabrics

The increasing demand for advanced personal protection systems has motivated a considerable interest in hybrid woven fabrics and textile composites. However, the effectiveness of the combination method of fibers on ballistic performance remains uncertain, leaving the selection of an appropriate hybridization strategy unresolved. This study conducted a thorough comparison of the ballistic responses of hybrid aramid/ultra-high molecular weight polyethylene (UHMWPE) woven fabrics, aiming to provide a comprehensive understanding of the hybridization effects. Specimens with inter-layer, intra-layer, and intra-yarn hybrid configurations were manufactured, and ballistic impact tests were performed via a light-gas gun. The residual velocity, energy absorption, dynamic penetration process, and perforation modes of the hybrid specimens were recorded at two selected impact velocities and then compared with those of non-hybrid specimens. The results demonstrated that the enhancement effect of hybridization varied with hybrid configuration and impact velocity. The interlacing of aramid yarns and UHMWPE yarns in intra-layer hybrid specimens did not promote the breakage of UHMWPE fibers, which was responsible for the inferior ballistic performance. In contrast, inter-layer hybridization and intra-yarn hybridization could overcome the insufficient friction of UHMWPE and the low mechanical properties of aramid, resulting in superior ballistic performance.

Geotechnical characteristics and seismic stability evaluation of pumice-fall deposits soil on collapse slope by the 2018 Hokkaido eastern Iburi earthquake

The September 6, 2018, earthquake in the eastern part of Hokkaido, Japan, caused extensive slope failures in Atsuma-town, Hokkaido, Japan. In this study, the authors performed in situ investigations, including trenching and portable dynamic cone penetration tests, on weathered fallen pumice sediments, which are one of the causes of the slope failures. In addition, we performed direct box shear tests on undisturbed samples collected from an undisturbed area under various shear conditions to characterize mechanical properties of the soil. The parameters obtained from the mechanical tests were used to evaluate slope stability under normal and seismic conditions with an infinite-length slope model. The results showed that the slopes where seismic failures occurred had a fragile layer from the surface to a depth of approximately 1.5 m, which generally corresponded to the depth of failure. Weathered pumice deposits with extremely high-water content existed at the boundary between the weak layer and the basement layer, and their shear strength was velocity dependent. It has been shown that an infinite-length slope stability analysis can be performed by using mechanical parameters for which velocity dependence of horizontal acceleration and shear strength due to seismic motion are accounted for.

Dynamic penetration behaviors of graphene origami under high-velocity impact

Brittleness remains the key bottleneck for graphene to be used as impact protection materials and this obstacle can be overcome by origami-modified graphene. Herein we employed molecular dynamics simulation to investigate the perforation behaviours of graphene origami (GOri) under ballistic impact from a diamond projectile. We found that the threshold penetration velocity of GOri can be improved significantly by 46.27 % compared with that of its pristine counterpart. Under a small ballistic impact loading at a low speed, GOri experiences a unique unfolding process and hence has improved impact-resistance performance. Depending on the initial velocity of the projectile, three different penetration phenomena are observed, i.e. bounce-back, capture, and perforation state. The penetration energy depends on the roughness of GOri, the initial impact velocity, the projectile's radius and the layer number. This study provides useful insights into the perforation behaviours and energy absorption of GOri and offers useful guidelines for graphene applications as impact protection materials.

Evaluation and analysis of liquefaction potential of gravelly soils using explainable probabilistic machine learning model

Majority of the presently available machine learning (ML) models employed to assess the liquefaction potential of soils are for sands or sands containing silt fraction. In the current study, an explainable ML (EML) model has been developed using the updated liquefaction database of gravelly soils. The Chinese dynamic cone penetration test (DPT) and shear wave velocity test results of gravelly soils are used in the analysis. A new empirical correlation between these two in-situ tests’ results is developed using the final processed database. The light gradient boosting machine (LightGBM) is trained using this processed dataset and further tuned using Fast and Lightweight AutoML library (FLAML). The final tuned model shows relatively better deterministic and probabilistic predictive performance for the test sites as compared to the conventional method. An EML technique, SHapley Additive exPlanations (SHAP) is applied to provide further comprehension into the predictions. The developed LightGBM-SHAP model has achieved a right balance between explainability and accuracy. The obtained SHAP plots are consistent with almost all the existing domain knowledge (DK) in gravelly soil liquefaction. The developed model thus fills the gap between the ML-based procedures and the traditional DK of gravelly soil liquefaction.

Comprehensive evaluation of strength parameters of soils by using DCP, DSCP, and LWD devices

ABSTRACT Traditionally evaluation of strength parameters of soil using plate load test is time-consuming, laborious and cumbersome process. This study is focused on evaluating the strength parameters of compacted soils, quickly and cost-effectively in terms of dynamic penetration index (DPI), dynamic resistance (DR), cone index (CI), and dynamic deformation modulus (E LWD ), analyzing their relationship with water content. Results, show strength parameters increases as water content decreases,with significant increase in DR, CI and E LWD for CBR changes from 5% to 10%, followed by marginal increase This study emphasized that the strength parameters vary with the physical properties of soils, for which correlations were proposed between CBR, DR, CI, and E LWD values, resulting in best-fit models. These parameters effectively indicate targeted in-situ strength conditions, aiding in assessing repeatability and uniformity of compaction. The mean DR, DPI, N, and E LWD were reported as 61.74 MPa, 6.41 mm/blow, 8 blows/100 mm, and 54.11 MPa, respectively from the field case study.

Applicability of shear wave velocity to evaluate state of granular materials with fines

Evaluation of state of cohesionless soils is a key issue in majority of geotechnical projects, especially when the major concern is liquefaction phenomenon. Standard approaches based on static or dynamic penetration tests are of limited or no use in granular materials containing considerable amount of fines. Therefore, there is a need to look for alternative approaches to identify state of materials containing certain amount of fines. One of a conceivable approaches rests on shear wave velocity (Vs) measurement. It results from the fact that Vs reflects state of stress and void ratio as well. A little is known to what extent shear wave velocity might reflect state of soil, especially, when it contains certain amount of fines. The paper concerns possibility of evaluation of state of cohesionless soils containing fines on the basis of shear wave velocity. The approach is based on hybrid approach i.e. laboratory and field measurement of shear waves velocity which enables projection of correlation between void ratio and normalized shear wave velocity measured in the laboratory for a given soil on a field profile. Thus, the determined void ratio profile is used to determine undrained shear strength on the basis of steady state line determined in the laboratory for the same soil batch. This procedure was carried out for twokinds of soil containing 10 and 36% of fines, which represent a sand-like material and transition zone behavior. Comments concerning applicability of this approach are given in the conclusion.

Local Stiffness Assessment of Geogrid-Stabilized Unbound Aggregates in a Large-Scale Testbed

This paper integrates and extends an earlier article presented at the 20th International Conference on Soil Mechanics and Geotechnical Engineering. The generation of a stiffened zone in the proximity of a geogrid is one of the primary mechanisms of mechanical stabilization of pavement unbound aggregate layers using geogrids. This paper focuses on the quantification of the stiffened zone through a local stiffness assessment using bender element (BE) sensors. Unbound aggregate base layers were constructed in a large-scale laboratory testbed. Geogrid-stabilized layers had geogrids with different-sized triangular apertures contributing to the geogrid-stiffened zone. Shear wave velocities were measured at three different heights using BE sensors, and the vertical stiffness profiles of the mechanically stabilized aggregate layers were evaluated. In addition, the conversion method between small-strain stiffness and large-strain stiffness was established from the repeated load triaxial tests with BE pairs to transform the vertical stiffness profile into that of the resilient modulus. Furthermore, dynamic cone penetration (DCP) and light-weight deflectometer (LWD) tests were performed at multiple locations into the stabilized and unstabilized unbound aggregates. From the large-scale experimental study, the local stiffness improvement owing to the geogrid enhancement was up to 16.2% in the vicinity of the geogrid location, and the extent of the local stiffened zone evaluated through various test methods was between 15.2 cm (6 in.) and 25.4 cm (10 in.) above the geogrid.

Free fall penetration test the undrained shear strength of submarine sediments

To perform in-situ testing of deep-sea sediment undrained shear strength, a novel free-fall penetrometer has been developed. This penetrometer is released from above the seabed and penetrates the sediments under gravity, resulting in intense interaction with the sediment. The study conducted free fall penetration tests in the Xisha area of the South China Sea, yielding the following achievements: (I) the establishment of a free-fall penetration governing equation, influenced by penetration attitude, along with the development of a model for undrained shear strength, revealed that at a 5° penetration angle, the sediment support force exceeded 100 N, and the undrained shear strength is approximately 40 kPa. (II) the relationship between dynamic penetration resistance coefficient and penetration velocity was inverted by the data from in situ test and laboratory. An error analysis revealed that inclined penetration and unreasonable penetration resistance coefficient can lead to errors exceeding 40 % in the test results.

Ballistic perforation of aramid laminates: Projectile nose shape sensitivity

The influence of projectile shape on the ballistic properties and mechanism of aramid laminates is investigated through experiments and simulations. Three types of projectiles (blunt, hemispherical, and ogival) are used to obtain ballistic curves. The dynamic penetration process, deformation and damage characteristics of the targets are analyzed. A three-dimensional finite element model is established, and good agreement is observed between the simulation and test results. The findings demonstrate that projectile shape significantly impacts the ballistic response of aramid laminates. As the projectile transitions from blunt and hemispherical to ogival, the ballistic limiting velocity decreases continuously, the area of target plate deformation and damage decreases, and the occurrence of delamination becomes less pronounced. And the energy dissipation through local damage, elastic deformation and overall motion of the aramid material is decreasing and the energy dissipation through friction is increasing.

Seismic-induced landslide hazard analysis of the recreational area of the Makiling Botanic Gardens, Los Baños, Laguna, Philippines

The Makiling Botanic Gardens (MBG) is an educational and eco-tourism site located within the vicinity of Mount Makiling, a dormant volcano susceptible to landslides, and located less than 20 km away from at least two tectonic faults. The study assessed the seismic-induced landslide hazards in the recreational area of MBG mainly based on three parameters: factor of safety (FS), yield acceleration (ay), and slope displacement (Dn). Dynamic Cone Penetration Test (DCPT) served as the primary method for obtaining the shear strength of the soil within the area. Meanwhile, other relevant parameters, including material unit weight and internal angle of friction, were determined through laboratory testing, correlations, and available data and models. Moreover, the Peak Ground Acceleration (PGA) and Spectral Acceleration (SA) values were obtained through an interpretation of a probabilistic seismic hazard analysis (PSHA) study of the Philippines. Using the ArcGIS software, an FS map, yield acceleration map, and slope displacement map were generated. Results showed that the slopes within the area exhibit static stability. However, in the event of an earthquake, it is expected that the amplified PGA will exceed the expected yield acceleration values of the slopes in some parts of the recreational area, which could result in dynamic instability and slope displacements as high as 130 mm. Thus, the recreational area of MBG possesses some susceptibility towards a seismic-induced landslide.

The Angle of the Shear Resistance of Danube Gravel Derived from the Dynamic Penetration Test

Abstract The dynamic penetration test was used to investigate the angle of shear strength of Danube gravel. The correlations for its determination are available in the standards and literature. From the data set of the results, the characteristic value of the angles of shear strength was derived according to the recommended statistical procedure from the second generation of Eurocode 7. The characteristic values of the angle of shear strength were evaluated for well-graded gravels, poor-graded gravels, and gravels with fine-grained particles of the Danube. The correlations, which were based on field tests and considered the genesis of the soil, were compared with laboratory test results and a table of the values from the Slovak standard, which are used for purposes of comparison. In our research we compared the characteristic field values of the angle of shear strength obtained in the laboratory to observe the effect of their genesis on the appropriateness of the correlations used. We conclude with recommendations for the regional correlations and suggest values of the angle of shear strength for the classes of gravels tested.