Surface Location Research Articles

Full-scale test and numerical modeling on deformation and damage behavior of segmental joints under ultimate compression-bending load

Investigating the deformation and damage behavior of segmental joints is of great significance for design optimization safety evaluation of shield tunnel. In this study, the full-scale tests of segmental joint under compression-bending load were carried out. A three-dimensional numerical calculation model with concrete damaged plasticity (CDP) constitutive was developed, of which the accuracy was validated by the full-scale test. The mechanical behavior and damage evolution process of the segmental joint, the strain of the bolt and the reinforcement are investigated. The experimental and numerical results revealed that the bending moment-rotational angle curves of segmental joint can be divided into four stages under positive bending moment and three stages under negative bending moment. The difference is mainly due to that the waterproof structure is only set outside the segmental joint. The maximum stress of the bolt occurred in the front of the thread rather than the corresponding location of the joint surface. Compared with Von Mises stress criterion, the method of judging the yield of bolt by the ultimate elastic strain usually adopted in the full-scale test is conservative. The bolt yields under negative bending moment later than that under positive bending moment, and the difference is about 49.8%. The maximum strain of the reinforcement is located at the first stirrup near the joint surface. The strain of the reinforcement at the sleeve side is obviously larger than that at the hand hole side under positive bending, while the opposite is true under negative bending.

Morphometric Examination of the Sacroiliac Region and Variable Positions of the Sacral Auricular Surface: Anatomical Classification and Importance.

Anatomical variations of the sacrum involve alterations in the number of sacral segments, auricular surface area, and neural arch dimensions and are associated with biomechanical, surgical, and obstetric implications. Due to the complex functional structure of the sacroiliac (SI) joints, it was aimed to evaluate their morphometric structure, classify the sacrum, and group different locations of the auricular surface in the sacrums. Sex determination was made in 91 dry human sacra. Determination of the alpha angle on the sagittal axis of the auricular surface of the sacrum and classification of the auricular surface of the sacrum wasperformed.The sacra were studied to determine the position and extent of their auricular surfaces in relation to the sacral segments. Specimens were grouped as "normal," "high-up," and "low-down" auricular surface-bearing sacra. The sacral surface areas were measured, and SI joints were classified into three types morphologically (types I, II, and III). The depth and anterior-posterior length of the cranial, middle, and caudal impressions observed in the posterior sacrum and anterior-posterior lengths were measured. The measurements made for sex determination showed that 46 of the sacra were from females and 45 were from males.The alpha angle on the sagittal axis of the sacral auricular surface was found to be greatest at the level of the first posterior sacral foramina. While the most common sacrum type was Type III, the least common type was Type I. The surface area of facies auricularis was found to be larger in males than in females. With regard to facies auricularis in all sacrum groups, although it covered approximately 2.5 sacral vertebrae, there was a difference in the location of facies auricularis in the sacral vertebrae. A statistically significant difference was found between right and left in the depth values of the impressions in the dorsal surface of the sacrum (p <0.05). The position of the auricular surface in the sacrum differed among individuals. These differences are associated with variable load-bearing in the SI joints. The biomechanical classification of the sacrum and localization of the auricular surface can provide information about the anatomic source of low back pain or help predict the location of low back pain. Changes in the synovial surface morphology of the SI joints may elicit sacroiliac joint pain. This study was conducted because it is considered that the location of the auricular surface can significantly affect load-bearing patterns of the sacrum.

Prediction of Surface Location Error Considering the Varying Dynamics of Thin-Walled Parts during Five-Axis Flank Milling

Surface location error (SLE) caused by forced vibration is a key factor to determine the quality of the finished part. When machining thin-walled structures with sculptured surfaces, the complicated milling process is significantly influenced by the vibration due to the flexibility of the part. The dynamics of the part are dominant and vary with the material removal during machining. This paper presents a prediction method of SLE considering the varying dynamics of thin-walled parts in five-axis flank milling. The in-process part is decomposed into unmachined and machined portions, which are both modelled based on the thin-plate theory. The dynamics models of the two portions are coupled using the substructure method. Coordinate transformation based on the screw theory and the general cutting dynamics model for five-axis flank milling is employed to transform the cutting force vectors and frequency response function (FRF) to the same coordinate system for the prediction of SLE. The proposed method is validated with five-axis flank milling tests and SLE measurements on a thin-walled twisted part. It is shown that the average error of the proposed method for SLE prediction is less than 5 μm, and the calculation is almost 8 times faster than the typical finite element method.

Study on the application of 3D printing head film fixation technology in cranial radiotherapy.

Objective: To investigate the use of 3D printing technology to customize individualized precise radiotherapy head masks for cranial radiotherapy patients. Through the comparison with thermoplastic head film, evaluate the effect of this material on deep dose attenuation and body surface dose, and evaluate its positioning accuracy and repeatability for clinical application. Methods: Thirty patients with head and neck radiotherapy were divided into the control group and the experimental group. The control group used the traditional thermoplastic head film fixation technique for body position fixation, and the experimental group used the 3D printing head film fixation technique. The patient setup was verified by kV-CBCT scanning to obtain the translational setup error and rotational setup error in the X, Y, and Z directions. Results: At a depth of 5 cm, both materials have a radiation attenuation rate of <1%. At the surface location, the body surface dose of control group increased by approximately 27%. With a 3D printing head film, the body surface dose increased by approximately 18%. The positioning of two groups of patients was verified by the kV-CBCT, and a total of 232 data sets were obtained. The average translation positioning errors in the X, Y, and Z direction of control group and experimental group were 1.29 mm, 1.42 mm, 1.38 mm and 1.16 mm, 1.24 mm, 1.16 mm, respectively. The average rotation positioning error in the X, Y, and Z direction of control group and experimental group were 1.29°, 1.02°, 1.01° and 1.08°, 0.96°, 1.00°, respectively. The translational setup errors in the Y and Z directions and rotational setup errors in the X direction significantly differed between the control and experimental groups (all p<0.05), but no statistical significance was found in the other directions (all p>0. 05). Conclusion: Compared to the traditional thermoplastic head membranes, 3D printing head membranes has shown a reliable and reproducible interactional positioning accuracy. Of course, further investigations are needed before the new technology can be used on a regular basis.

Directly tracing the vertical stratification of molecules in protoplanetary disks

Context. The specific location from where molecules emit in a protoplanetary disk depends on the system properties. Therefore, directly constraining the emitting regions radially, azimuthally, and vertically is key to studying the environment of planet formation. Due to the difficulties and lack of high resolution observations, most of the current observational constraints for the vertical distribution of molecular emission rely on indirect methods. Aims. We aim to directly trace the vertical location of the emitting surface of multiple molecular tracers in protoplanetary disks. Our sample of disks includes Elias 2-27, WaOph 6, and the sources targeted by the MAPS ALMA Large Program. The set of molecules studied includes CO isotopologues in various transitions, HCN, CN, H2CO, HCO+, C2H, and c-C3H2. Methods. The vertical emitting region is determined directly from the channel maps by tracing the location of emission maxima along the upper surface. This method has been used in previous studies, but here we implement an accurate masking of the channel emission in order to recover the vertical location of the emission surface even at large radial distances from the star and for low-S/N lines. Parametric models are used to describe the emission surfaces and characterize any structure within the vertical profile. Results. The vertical location of the emitting layer is obtained for ten different molecules and transitions in HD 163296. In the rest of the sample it is possible to vertically locate between four and seven lines. Brightness temperature profiles are obtained for the entire sample and for all CO isotopologues. IM Lup, HD 163296, and MWC 480 12CO and 13CO show vertical modulations, which are characterized and found to be coincident with dust gaps and kinematical perturbations. We also present estimates of the gas pressure scale height in the disks from the MAPS sample. Compared to physical-chemical models, we find good agreement with the vertical location of CO isotopologues. In HD 163296, CN and HCN trace a similar intermediate layer, which is expected from physical-chemical models. For the other disks, we find that UV flux tracers and the vertical profiles of HCN and C2H are lower than predicted in theoretical models. HCN and H2CO show a highly structured vertical profile, possibly indicative of different formation pathways in the case of H2CO. Conclusions. It is possible to trace the vertical locations of multiple molecular species that in turn trace a wide variety of physical and chemical disk properties. The distribution of CO isotopologues is in agreement with theoretical predictions, and the emission is found at a wide range of vertical heights, z/r = 0.5–0.05. The vertical location of CO may be inversely related to the stellar mass. Other molecular lines are mostly found at z/r ≤ 0.15. The vertical layering of molecules is in agreement with theoretical predictions in some systems, but not in all. Therefore, dedicated physical-chemical models are needed to further study and understand the diversity of the emission surfaces.

Digital rock workflow to calculate wettability distribution in a reservoir rock

Wettability has a strong influence on multi-phase flow behavior through reservoir rock. Reservoir rocks tend to have spatially varying wettability. Prior to contact with oil, rocks are almost always naturally water-wet. As oil invades the pore-space over geologic time, the initial water-wet state may be altered in certain locations due to adhesion of substances within the oil phase to the grains. Mechanisms of wettability alteration depend on various properties such as pressure, temperature, mineral chemistry, surface roughness and fluid composition. In this study wettability alteration in a reservoir rock is studied through direct simulation using multiphase Lattice Boltzmann method where the computational grid is constructed from segmented micro-CT images of the rock sample. The pore-grain interface is defined by a triangulated surface mesh for accurate fluxes near boundary and local curvature calculation. A capillary pressure drainage simulation is conducted in a water-wet Berea sandstone sample initially filled with water. When oil invades the pore space as the capillary pressure is increased, a fraction of the pore-grain surface is altered towards an oil-wet condition, as determined by a novel wettability alteration process. This process calculates local curvature at every surface element of the rock, obtains local capillary pressure from the simulation and assumes a disjoining pressure to determine water-film breakage at every location of the pore-grain surface. As a result, a spatially varying rock wettability is created. Using this new wettability distribution, the simulation is continued to allow the fluid phases to redistribute accordingly. The process is iteratively carried out until both fluid saturation and wettability distribution converged at a given applied capillary pressure. Afterwards, the pressure is ramped up to the next stage and the process is repeated again. It has been found that the wettability alteration is a slow dynamic process where the non-wetting phase can gradually invade finer pore space as the surrounding grain wettability is altered. In this study, it has also been found that wettability alteration of the reservoir rock produces lower connate water saturation during primary drainage compared to the simulation results without alteration. The resulting spatially varying wettability distribution from primary drainage is used for a subsequent water flooding simulation to calculate water-oil relative permeability curves. The methodology presented in this work can be leveraged to better understand and predict an improved mixed wetting conditions found in the reservoir rocks which is needed for more accurate displacement tests such as relative permeability simulations.

Alterations of motor unit characteristics associated with muscle fatigue.

This study aims to characterize motor unit (MU) features associated with muscle fatigue, using high-density surface electromyography (HD-sEMG). The same MUs recruited before / after, and during muscle fatigue were identified for analysis. The surface location of the innervation zones (IZs) of the MUs was identified from the HD-sEMG bipolar motor unit action potential (MUAP) map. The depth of the MU was also identified from the decay pattern of the MUAP along the muscle fiber transverse direction. Both the surface IZ location and the MU depth information were utilized to ensure the same MU was examined during the contraction before / after muscle fatigue. The MUAP similarity, defined as the correlation coefficient between MUAP morphology, was adopted to reveal the alterations in MU characteristics under the condition of fatigue. The biomarkers of the same MUs were compared before / after fatigue (task 1) at 5%, 10%, and 15% maximal voluntary contraction (MVC) and in the process of continuous fatigue (task 2) at 20% MVC. Our results indicate that the MUAP morphology similarity of the same MUs was 0.91 ± 0.06 (task 1) and 0.93 ± 0.04 (task 2). The results showed that MUAP morphology maintained good stability before / after, and during muscle fatigue. The findings of this study may advance our understanding of the mechanism of MU neuromuscular fatigue.

Features of projection surface locations in construction engineering in different countries

Engineering graphics is a real language that allows people from different countries to talk to each other, but today it is not universal. In this paper, the authors set out to identify differences in techniques and approaches to projecting objects onto different surfaces. Different countries use different systems, as well as with the International System of Units, which has been used successfully since the last century. The projection of detail in the European part of the world is significantly different than in the western hemisphere. The “European” method of projection formation assumes an opaque projection plane behind the projected object; the “American” method assumes that there is a transparent projection plane between the observer and the object, and the projection rays are directed towards the observer. An experiment was conducted in Russia to teach schoolchildren a particular system, which showed the complexity of the “American” projection system. In the future, countries that will enter a large agglomerate to solve global problems will benefit from creating a common projection standard that takes into account the views and interests of the world scientific and engineering community. This step will improve the speed of communication and design of new technical complexes, as well as eliminate possible mistakes when working in a large, multinational team.

Optimization of site investigation program for reliability assessment of undrained slope using Spearman rank correlation coefficient

Site investigation programs (e.g., boreholes) are crucial in characterizing soil properties and stratigraphic configurations. However, the traditional borehole patterns are generally of equally spaced distribution for the slope design, and the locations and total number of boreholes are considerably determined depending on engineers’ experience, which may lead to cost-inefficient geotechnical design, especially considering the soil spatial variability. To address this dilemma, this paper presents a Spearman rank correlation coefficient-based scheme to optimize site investigation in slope design, where both locations and total number of boreholes are optimized. Conditional random field simulations are performed to consider the effect of the borehole data on the estimation of the soil property distribution. The superiority of the proposed method to the traditional method is illustrated by a comparison study in an undrained slope example. In this example, the accuracy of the characteristics of the slope (i.e., the factor of safety, location of slip surface, and sliding volume), robustness of the estimated characteristics of the slope, and risk reduction are examined. The comparison results show the effectiveness of the proposed method in accurately estimating the characteristics of the slope without prior knowledge about the slip surface, since the slip surface is unknown for most practical cases prior to the site investigation. The most robust estimate results and risk reduction are obtained using the proposed method. This study can also provide useful references to build an adaptive unequally spaced borehole pattern in practice.

Epidermal Structure and Leaf Stomata of Several Accessions of Banana Plants (Musa spp.)

This study aimed to determine the structure of epidermal cells and leaf stomata in Jarum, Merah, Tanduk, Kepok, and Pei or wild banana. The type of research used was quantitative to calculate the number of epidermis, epidermal cell size, number of stomata, and stomata index. Meanwhile, qualitatively described the structure of epidermal cells, epidermal cell shape, stomata shape, and stomata type of banana leaves based on the longitudinal incision method. The results showed that four accessions of bananas have epidermal cell shapes: rectangular, pentagon, hexagon, heptagon, octagonal, and regularly length. Meanwhile, Merah have different epidermal cell shapes, namely rectangular, pentagon, hexagon, and irregular, with untidy arrangements. The stomata of the five samples are surrounded by four to six subsidiary cells and are kidney-shaped. Based on the location of the leaf surface, stomata in five banana accessions have an amphistomatic type. Pei or wild bananas have a long epidermal size compared to the other four species but have a small number of epidermis. Then, the number of stomata in all banana species differs on the upper and lower surfaces. The number of stomata is more on the lower surface of the leaves. Stomata index in all banana species is low

Integrating Protein Interaction Surface Prediction with a Fragment-Based Drug Design: Automatic Design of New Leads with Fragments on Energy Surfaces.

Protein-protein interactions (PPIs) have emerged in the past years as significant pharmacological targets in the development of new therapeutics due to their key roles in determining pathological pathways. Herein, we present fragments on energy surfaces, a simple and general design strategy that integrates the analysis of the dynamic and energetic signatures of proteins to unveil the substructures involved in PPIs, with docking, selection, and combination of drug-like fragments to generate new PPI inhibitor candidates. Specifically, structural representatives of the target protein are used as inputs for the blind physics-based prediction of potential protein interaction surfaces using the matrix of low coupling energy decomposition method. The predicted interaction surfaces are subdivided into overlapping windows that are used as templates to direct the docking and combination of fragments representative of moieties typically found in active drugs. This protocol is then applied and validated using structurally diverse, important PPI targets as test systems. We demonstrate that our approach facilitates the exploration of the molecular diversity space of potential ligands, with no requirement of prior information on the location and properties of interaction surfaces or on the structures of potential lead compounds. Importantly, the hit molecules that emerge from our ab initio design share high chemical similarity with experimentally tested active PPI inhibitors. We propose that the protocol we describe here represents a valuable means of generating initial leads against difficult targets for further development and refinement.

A novel approach to estimating urban land surface temperature by the combination of geographically weighted regression and deep neural network models

Growing concerns on excessive urban heat call for better approaches to modeling urban thermal environment and developing effective mitigation strategies. A hybrid model integrating the geographically weighted regression (GWR) and deep neural network (DNN) was developed to estimate land surface temperature (LST). This model was compared with three other data-driven approaches to predicting LST, including the ordinary least squares (OLS) regression, GWR, and DNN. Sixteen satellite image datasets (a total of 155,728 data points) during a four-year period in Hong Kong were used for model development, validation, and comparison. The datasets cover two distinguishable geographical regions and consist of sixteen explanatory variables from five groups, including (1) land use and land cover (LULC) composition and surface characteristics, (2) LULC configuration, (3) urban form, (4) anthropogenic activities, and (5) location and local climate. The results indicate that the hybrid model performs the best in terms of model fitness and prediction accuracy, with R2 equal to 0.85 and 0.73 and the mean squared error (MSE) equal to 0.52 and 0.70 in the two regions, respectively. Compared to the OLS, DNN, and GWR models, the overall R2 for all the datasets of the hybrid model increases by 97.3%, 16.6%, and 6.9%, respectively. The promising result of the hybrid model is due to its ability to capture both spatial heterogeneity and address possible correlations between explanatory variables. Sensitivity of LST to various explanatory variables is also discussed and strategies to mitigate excessive heat are recommended. This study is anticipated to contribute to model development in urban LST estimation and quantitative evaluation of those factors driving LST variations.

Extent of the frontal sinuses in the aspect of neurosurgical craniotomy approaches.

Frontal sinuses within the frontal bone can be a potential obstacle in neurosurgical approach in this region. Their unintended opening during craniotomy is not beneficial due to the risk of brain infections by bacteria inhabiting the sinus mucosa. Therefore, such opening should be avoided whenever the surgical procedure does not involve the sinus itself. The aim of the study was the morphometric analysis of the frontal sinuses based on computed tomography imaging. The width, height, projection surface area and location of the highest and most lateral points of the sinuses were determined. The vertical diameter of the sinuses was found to be greater in men compared with women. The most lateral point of the sinuses was located higher in men, and in men was located higher on the left side. The results obtained may indicate that the frontal sinuses tend to be larger in men and that air cells in men extend further in the upper-lateral direction on the left side of the frontal bone. This may cause an increased risk of unintentional opening of the left frontal sinus during frontal craniotomy or pterional craniotomy with frontal extension.

Mathematical Modeling of Transient Electromagnetic Sounding Signals for Monitoring the State of Permafrost

Abstract —The study is aimed at theoretical development and scientific substantiation of a high-resolution transient electromagnetic (TEM) geophysical technique for monitoring the state of permafrost. The electromagnetic monitoring configuration includes spatially distributed sounding systems for surface and borehole locations of the field sources and receivers. Changes in the electrophysical properties of the earth can be traced for the cases of both ground thawing and freezing. We developed the theory of TEM signals modeling, upon which created an algorithm for rapid and accurate numerical simulation of the electromagnetic field. The signals are scrutinized from the various sounding systems in the basic earth models as function of registration time. We show how the features associated with a spatial arrangement of frozen rocks appear on the EMF diagrams. It follows that a set of the measured data enables visual detection of the boundary between frozen and thawed rocks.

Numerical Study of Heat Transfer Characteristics of Impinging Syngas Flames From Multi-Slot Burner

Abstract Characteristics of impinging flames from a multi-slot burner fueled by synthetic gas are studied using a comprehensive numerical model. A multi-slot burner with five fuel slots and six air slots arranged in an alternately has been analyzed. The power rating of the burner is kept at 10 kW, and the air flowrate is fixed at 400% of the stoichiometric air required for the net fuel flowrate. The numerical model incorporates a short chemical kinetic mechanism, variable thermophysical properties, full multicomponent diffusion, thermal diffusion and a radiation sub-model. The location of the solid surface from the burner exit, primary air in fuel stream, dimensions of solid surfaces, and their temperatures have been varied to study the heat flux distributions from impinging flames. Results show that the location of the solid surface from the burner ports and partial premixing affect the heat transfer characteristics. The heat fluxes received by the side and top surfaces depend on the characteristics of neighboring flames located around the central flame. The heat flux distribution and the net heat flux received by the surface are found to be uniform and optimum at a height of 90 mm from the burner exit. Increasing the length of the impinging surface has negligible influence on average heat flux and CO production. The mass fraction of CO is affected by heating height and partial premixing. It remains almost constant for varying temperatures of the impinging surfaces. Primary aeration of 20% is found to be optimum for higher net heat flux and lower CO emissions.

Simplified method for analyzing soil slope deformation under cyclic loading

Reasonable assessment of slope deformation under cyclic loading is of great significance for securing the safety of slopes. The observations of centrifuge model tests are analyzed on the slope deformation behavior under cyclic loading conditions. The potential slip surface is the key for slope failure and follows two rules: (i) the relative horizontal displacement along the potential slip surface is invariable at an elevation, and (ii) the soil along the slip surface exhibits the same degradation pattern. These rules are effective regardless of the location of the potential slip surface throughout the entire deformation process of a homogeneous slope, ranging from the initial deformation stage to the failure process and to the post-failure stage. A new, simplified method is proposed by deriving the displacement compatibility equation and unified degradation equation according to the fundamental rules. The method has few parameters that can be determined through traditional element tests. The predictions from the proposed method agree with the centrifuge test results with vertical loading and shaking table loading. This result confirms that the proposed method is effective in predicting the full deformation process of slopes under different cyclic loading conditions.

Case Study: Hitting the Bullseye: The Evolution of RSS and LWD Technology in Horizontal Wells

_ For nearly a century, conventional directional drilling served as the benchmark for drilling nonvertical wellbores. It enabled operators to access multiple parts of a reservoir from a single surface location, reducing the overall environmental impacts. Traditional directional drilling used some type of nonrotating bent sub to tilt the drill bit in a different direction from the central axis. But with the demands of the modern energy industry driven by the unconventional horizonal well market, the industry needed a step change. Operators required a system that could precisely steer through extended-reach wells, often traversing complex trajectories, with precision control and greater reliability. The evolution of rotary steerable systems (RSS) and logging-while-drilling (LWD) technology in the early 2000s addressed this demand by deploying fit-for-purpose tools and services to improve the economic viability of oil and gas fields around the world. High-Performance Drilling With Full Directional Control With more operators needing an RSS system that could drill through longer horizontals and deliver quality wellbores in as few runs as possible, Weatherford recognized the demand and responded with the Magnus RSS. Using a push-the-bit design, the system combines reliable, high-performance drilling with precise directional control to enable operators to extend the performance of each drilling run, providing faster drilling, better wellbore quality, and high-quality measurements. Directional drilling requires tools to stay in the wellbore for extended periods of time. To keep costs as low as possible, the optimal solution is to perform all drilling operations in one run. To account for the downhole stresses, a rugged design was developed for the RSS. A streamlined design, featuring a ¼-in. undergauge stabilizer and 20% junk-slot area, a fully rotating bias unit, minimal bottomhole assembly (BHA) stabilization, and an optimized junk-slot area combine to reduce the risk of expensive stuck-pipe events. The system also incorporates metal-on-metal piston seals in the mud-actuated pad, enhancing mechanical integrity in harsh and high-pressure drilling environments and greater overall system reliability. Operators also need the ability to precisely steer the bit to stay on the well plan no matter if the plan requires verticals, curves, or laterals. Three independent pads and valves provide proportional control and allow the pads to fully retract for reaming, cement/shoe drilling, or tight-hole applications. This independence also provides redundancy in the system in the event of pad or valve failure. The three pads actively manage the direction through the entire wellbore and achieve a true-inclination hold in the lateral. In many conventional directional drilling operations, even a successful run can leave the wellbore in need of underreaming to prepare it for the installation of contingency liners and casing or completions equipment. Ideally, to optimize drilling efficiency, the directional drilling and underreaming should be performed in the same run. To meet operators’ desire for hole enlargement while drilling, our engineers developed the RipTide drilling reamer, which is often coupled with the Magnus RSS, to drill a smooth, concentric underreamed hole to total depth in one trip.

Efficient simulation of stochastic seismic response of long-span bridges in river valleys using hybrid BEM-FEM

Determining ground motions is essential for seismic analysis of long-span bridges located at complex sites. However, there is a lack of earthquake records for local site conditions. Thus, this study focused on the effect of local site conditions on the stochastic response of long-span high-pier rigid frame bridges crossing a valley with an overlying water layer. For this purpose, a hybrid boundary element and finite element method (BEM-FEM) is proposed to investigate the stochastic seismic response of long-span bridges at such a complex site. First, a simulation method for 3-D spatially varying ground motions ascribed to wave scattering from irregular surface topography, sedimentary soil, and water layers was established based on the BEM combined with the spectral representation method. Furthermore, the statistical properties of the bridge response were explored based on the FEM and Monte Carlo simulations. The advantage of this work is that it reveals how the seismic wave propagation in this particular valley topography and water layer affects the stochastic response of the bridge considered. Moreover, the results indicate that seismic wave scattering leads to a significant energy redistribution of the input waves in the tri-directions related to the surface location, and a decrease in the coherency loss functions at all frequencies. Owing to this change, the peak ground accelerations (PGAs), bridge response means, and response variability are doubled. The beneficial effect of the water layer on the PGAs is weakened, while the adverse effect of hydrodynamic pressure dominates. The parameter analysis results demonstrate that a 10-m-deep sedimentary soil layer produces a 47% increase in the internal force of the pier bottom. The solid-liquid dynamic coupling effect should be accurately quantified for bridges located at saturated sites. Considering the local site conditions, the coefficient of variation (COV) of the response of the pier top exceeded 0.3, indicating strong randomness.

Upper-bound solutions for the soil thrust of clay under a track system in 3D conditions

This study proposes a quick and reliable method for estimating the soil thrust in clay ground for a tracked vehicle based on limit analysis in three-dimensional conditions. With respect to the shape and location of failure surfaces in clayey ground, block, triangular wedge, and trapezoidal wedge failure modes were considered. Between the upper-bound solutions from the different failure modes, the least upper-bound solution was proposed as the soil thrust. To verify the proposed solution, it was compared to the model test and numerical simulations for a track system over model clay ground. The proposed upper-bound solution is expected to produce a reliable soil thrust quickly in real time, especially for submerged heavy-weight remotely operated vehicles (ROVs).

Experimental study on shear characteristics of the silty clay soil-ice interface

During the spring thawing, the decrease of soil-ice interface strength by temperature may lead to slope instability. For this reason, some researchers have explored the relationship between temperature and soil-ice interface strength. However, previous studies have not systematically explored the change law of strength at the soil-ice interface from negative temperature to 0 °C. Therefore, direct shear tests were conducted at different shear temperatures and different moisture contents. The effects of temperature and moisture content on strength, cohesion, and internal friction angle are analyzed, while the shear failure mechanism of specimens at different temperatures is discussed according to the location of the shear failure surface. The results show that: Shear properties of soil ice specimens are related to the unfrozen moisture content. The strength of the sample decreases with increasing temperature, and the change in strength is most significant from − 2 to − 0 °C. The strength reduction in this range is from 21.8 to 74.8%, and the higher the moisture content the more obvious this phenomenon is. The shear index tends to decrease with the increase of unfrozen water content, and the greater the increase of unfrozen water, the faster the decrease of both, especially in stage 2. When the temperature is higher than − 5℃, the failure surface is located above the soil-ice interface, and the strength of the specimen is similar to that of the frozen soil. When the temperature is − 10℃, the shear damage surface appears at the soil-ice interface, and the strength of the specimen is determined by the strength of the soil-ice interface.