Outward Movement Research Articles

Investigation of comparative entropy in different nanofluids inspired by solar radiations and unsteady effects: Model analysis for permeable channel

Entropy analysis in nano as well as conventional fluids is of paramount interest and highly affected by the active physical quantities. The research provides comprehensive comparative entropy performance of multiple nanofluids in the view of model quantities. The physical model considered in the presence of solar radiations, dissipation energy and magnetic field. The multiple fluids squeezed in a channel formed by two horizontal sheets with upper non-stationary surface. The entropy modeling performed using similarity variables for transient flow and governing laws. The numerical approach (RK method coupled with shooting scheme) is used for entropy results which obtained for ternary, hybrid, nano and base fluids. It is found that entropy optimized in ternary nanofluid while hybrid, nano and common fluids caused reduction in it. Dissipation effects (Ec=0.1,0.3,0.5,0.7) increases the entropy while significant reduction is observed for Ω1=0.1,0.2,0.3,0.4. The solar radiations in the range of Rd=1.0 to Rd=7.0 contributes effectively to improve entropy phenomena in both inward and outward plate movement. Thus, the system can be maintained at low entropy by strengthening the effects of Ω1 and optimum entropy is subject to Eckert number, α=0.1,0.2,0.3,0.4, radiations (Rd=1.0,3.0,5.0,7.0) for S>0.0 and S<0.0, respectively.

Incorporation of Mg/Al metal oxide into ionic liquids for CO2 capture and conversion into cyclic carbonate under solvent-free conditions: effect of coordination ability, recyclability, and catalytic study

The direct conversion of carbon dioxide (CO2) and propylene oxide (PO) into propylene carbonate (PC) offers a green way to utilize anthropogenic CO2. However, this reaction is limited by low conversion of PO and harsh reaction conditions. In this study, we solve this problem using ionic liquids (ILs)/metal oxide composites (ILs@MAO). The catalytic activity of MAO-500 (500 = annealing temperature) is poor evidenced by its low conversion of PO (24.94%). However, ILs@MAO-500 has a high conversion of PO (97.54%) under similar reaction conditions (2 h at 1.5 MPa CO2 pressure, 90 oC, and 0.85 g catalyst). The ILs consist of imidazolium cation with weak coordinated [NTf2]- anion leading to outward movement of anion resulting in the formation of “heterodinuclear complex”. This complex generates an amorphous-crystalline intermediate with balanced acid-base sites that activate PO and stabilize the catalytic intermediate. The high PO conversion is theorized to be primarily due to in large part the abundant reactive sites in the ILs that are covalently immobilized on the MAO-500 carrier. Furthermore, even after multiple recycling, ILs@MAO-500 remains stable and exhibits high yield and selectivity. The proposed solvent-free catalytic system is mild, kinetically fast, and naturally safe for coupling CO2 and PO into PC synthesis.

Mapping and engineering RNA-controlled architecture of the multiphase nucleolus.

Biomolecular condensates are key features of intracellular compartmentalization. As the most prominent nuclear condensate in eukaryotes, the nucleolus is a layered multiphase liquid-like structure and the site of ribosome biogenesis. In the nucleolus, ribosomal RNAs (rRNAs) are transcribed and processed, undergoing multiple maturation steps that ultimately result in formation of the ribosomal small subunit (SSU) and large subunit (LSU). However, how rRNA processing is coupled to the layered nucleolar organization is poorly understood due to a lack of tools to precisely monitor and perturb nucleolar rRNA processing dynamics. Here, we developed two complementary approaches to spatiotemporally map rRNA processing and engineer de novo nucleoli. Using sequencing in parallel with imaging, we found that rRNA processing steps are spatially segregated, with sequential maturation of rRNA required for its outward movement through nucleolar phases. Furthermore, by generating synthetic de novo nucleoli through an engineered rDNA plasmid system in cells, we show that defects in SSU processing can alter the ordering of nucleolar phases, resulting in inside-out nucleoli and preventing rRNA outflux, while LSU precursors are necessary to build the outermost layer of the nucleolus. These findings demonstrate how rRNA is both a scaffold and substrate for the nucleolus, with rRNA acting as a programmable blueprint for the multiphase architecture that facilitates assembly of an essential molecular machine.

Structural changes of Natronomonas pharaonis halorhodopsin in its late photocycle revealed by solid-state NMR spectroscopy

Natronomonas pharaonis halorhodopsin (NpHR) is a light-driven Cl− inward pump that is widely used as an optogenetic tool. Although NpHR is previously extensively studied, its Cl− uptake process is not well understood from the protein structure perspective, mainly because in crystalline lattice, it has been difficult to analyze the structural changes associated with the Cl− uptake process. In this study, we used solid-state NMR to analyze NpHR both in the Cl−-bound and -free states under near-physiological transmembrane condition. Chemical shift perturbation analysis suggested that while the structural change caused by the Cl− depletion is widespread over the NpHR molecule, residues in the extracellular (EC) part of helix D exhibited significant conformational changes that may be related to the Cl− uptake process. By combining photochemical analysis and dynamic nuclear polarization (DNP)-enhanced solid-state NMR measurement on NpHR point mutants for the suggested residues, we confirmed their importance in the Cl− uptake process. In particular, we found the mutation at Ala165 position, located at the trimer interface, to an amino acid with bulky sidechain (A165V) significantly perturbs the late photocycle and disrupts its trimeric assembly in the Cl−-free state as well as during the ion-pumping cycle under the photo-irradiated condition. This strongly suggested an outward movement of helix D at EC part, disrupting the trimer integrity. Together with the spectroscopic data and known NpHR crystal structures, we proposed a model that this helix movement is required for creating the Cl− entrance path on the extracellular surface of the protein and is crucial to the Cl− uptake process.

Structural Rearrangement of the AT1 Receptor Modulated by Membrane Thickness and Tension.

Membrane-embedded mechanosensitive (MS) proteins, including ion channels and G-protein coupled receptors (GPCRs), are essential for the transduction of external mechanical stimuli into biological signals. The angiotensin II type 1 (AT1) receptor plays many important roles in cardiovascular regulation and is associated with diseases such as hypertension and congestive heart failure. The membrane-mediated activation of the AT1 receptor is not well understood, despite this being one of the most widely studied GPCRs within the context of biased agonism. Here, we use extensive molecular dynamics (MD) simulations to characterize the effect of the local membrane environment on the activation of the AT1 receptor. We show that membrane thickness plays an important role in the stability of active and inactive states of the receptor, as well as the dynamic interchange between states. Furthermore, our simulation results show that membrane tension is effective in driving large-scale structural changes in the inactive state such as the outward movement of transmembrane helix 6 to stabilize intermediate active-like conformations. We conclude by comparing our simulation observations with AlphaFold 2 predictions, as a proxy to experimental structures, to provide a framework for how membrane mediated stimuli can facilitate activation of the AT1 receptor through the β-arrestin signaling pathway.

Dark resonance: On the possibility of resonance with death

The concept of resonance, introduced by Hartmut Rosa, denotes a vital relationship to the world and offers a starting point for discussing meaningfulness in peoples’ lives by serving as an antithesis to alienation. An unexplored aspect of the concept is the potential for resonance with death, which Rosa dismisses as an impossibility. This article challenges this view by introducing the term dark resonance, based on the ‘dark turn’ in the philosophy of nature. Dark resonance comes in (at least) two variants, both implying a transcendence of the self: (1) as reunion, an implosion of the self and an inwards movement, and (2) as release, an explosion of the self and an outwards movement. For both variants, the borders between self and environment and between life and death, becomes fuzzy, which also challenges the idea that resonance demands an experiencing subject. These variants are explored through examples from black metal, palliative care and near-death experiences. An implication is that we may need to broaden the scope of what can be seen as desirable ways of connecting to the world and acknowledge that there is potential for resonance also in dark thoughts, or, in some cases, even in death.

The preliminary study of the effects of individual musculoskeletally stable position in the treatment of temporomandibular disorders

BackgroundTemporomandibular Disorders (TMD) is the dysfunction of group of muscles and bones in the joint area, the main symptoms of TMD are the pain of the chewing muscles and (or) the temporomandibular joints, mandibular movement disorders and joint noise. This study was designed to explore the therapeutic effects following Individual Musculoskeletally Stable (IMS) position stabilization splint therapy for TMD patients using Fricton index, cone beam computed tomography (CBCT) and surface-Electromyogram (sEMG).MethodsIn this study, we enrolled 31 TMD patients (ranging from 18 to 26 years old, including 7 males and 24 females), first Fricton index was used to evaluate the clinical curative effect of TMD with the treatment of IMS stabilization splint; then CBCT was used to observe the TMJ condylar position changes of TMD before and after the treatment of IMS stabilization splint; finally sEMG was used to observe the changes of electromyography of anterior temporalis (AT) and masseter muscles (MM) of TMD before and after the treatment of IMS stabilization splint.ResultsThe course of treatment was 6–8 months, with an average of 7.6 months. After the IMS stabilization splint treatment, TMD symptoms relieved, especially in pain, mandibular movement disorder, but still slightly inferior in the treatment of joint noise. And there was a statistically significant difference in the anterior and inner joint space, the condyle had the tendency of moving forward and outward. AT presented reduction significantly of EMG value at rest position after treatment.ConclusionsIMS stabilization splint is a therapeutic reversible treatment for TMD, especially for pain and mandibular movement disorder; it produces effects of forward and outward condylar movement and elimination of the masticatory muscles antagonism.

Comparing Line-Field Confocal Optical Coherence Tomography and Reflectance Confocal Microscopy on the In Vivo Healing Process of Lesions Induced by Fractional Photothermolysis.

The advent of ablative fractional photothermolysis has revolutionized laser dermatology by providing a method to produce well-standardized, precise, and repeatable microscopic lesions. These wounds typically heal within 1-3 weeks, depending on the body site, with a minimal risk of permanent scarring. This positions ablative fractional photothermolysis as an exemplary in vivo model for studying the skin's wound healing processes. This study aims to evaluate and compare the effectiveness of two noninvasive imaging techniques, reflectance confocal microscopy (RCM) and line-field confocal optical coherence tomography (LC-OCT), in assessing skin wound healing following microscopic injuries induced by ablative fractional photothermolysis. The forearms of participating volunteers were treated and ablated with a CO2-Laser in a fractional pattern using varying power settings (2.5-10 mJ/MTZ). In vivo RCM and LC-OCT images were obtained at predefined time intervals post-laser treatment, ranging from 6 h to 14 days. Vertical visualization of the lesions through both imaging modalities revealed a healing process characterized by the upward and outward movement of microscopic epidermal necrotic debris, thereby reducing the depth of the injury while forming an external crust. LC-OCT imaging demonstrated more comprehensive results with fewer movement artifacts. Conversely, horizontal visualization with both techniques highlighted a gathering of keratinocytes around the wounds, indicating the initiation of the regenerative process. RCM provided superior image clarity in this horizontal plane. RCM and LC-OCT offer valuable and complementary noninvasive alternatives to conventional biopsy methods for the assessment and characterization of the skin's wound healing process post-ablative fractional photothermolysis. These findings underscore the potential of such imaging techniques in enhancing our understanding of the wound healing process. ClinicalTrials.gov identifier: NCT05614557.

Reading Austen’s Fiction as Modern: Women’s Outward and Social Movements in Jane Austen’s Novels

Reading Austen’s Fiction as Modern: Women’s Outward and Social Movements in Jane Austen’s Novels

Improving the oxidation resistance by forming continuous Al2O3 protective layer in alumina-forming austenitic stainless steel

The effect of varying aluminum (Al) levels on the high-temperature oxidation resistance of Alumina-Forming Austenitic stainless steels (AFA) has been investigated under dry air conditions at 800 °C and 900 °C. Mass gain assessments indicate that AFA stainless steel containing a higher concentration of Al, with a composition of Fe-20Ni-15Cr-2.4Al-1.6Mn, demonstrates enhanced resistance to oxidation when contrasted with steel of lower Al content, characterized as Fe-23Ni-15Cr-1.9Al. This phenomenon is attributed to the development of a compact CrMn1.5O4 layer on the exterior and an Al2O3 layer on the interior. The dense oxide layers that form on the high-Al steel impede the permeation of oxygen and deter the peeling of the oxide layer, thus preserving structural stability of the material upon exposure to high temperatures. Conversely, the steel with a lower Al content undergoes considerable chipping of its oxide layer. The morphology and distribution of Al2O3 are determined by the relative rates of oxygen inward movement and aluminum outward movement. In the case of the Fe-20Ni-15Cr-2.4Al-1.6Mn steel, the tight oxide film significantly reduces the inward movement of oxygen and increases the outward movement of Al, leading to a denser Al2O3 layer underneath the Cr2O3.

MICROSTRUCTURE AND PROPERTIES OF 6082/7075 MAGNETIC-FIELD-ASSISTED RESISTANCE-SPOT-WELDED JOINTS

To advance automotive lightweighting, a study was conducted on steady-state magnetic-field-assisted resistance spot welding of 6082 aluminum alloy (1.0 mm thick) and 7075 aluminum alloy (1.5 mm thick) with thermal compensation. The influence of varying magnetic induction intensity on the microstructure and tensile properties of welded joints was assessed under the same welding current, time and electrode pressure. The results revealed that the Lorentz force induced by magnetic induction intensity ranging from 0 mT to 60 mT could promote an outward circumferential movement of molten metal within the weld nugget. This movement, at the same time, led to an increase in the weld-nugget size and improved the efficiency of thermal resistance. At a magnetic induction intensity of 80 mT, no weld-nugget formation occurred in the welded joint. Microstructural observations at magnetic induction intensities of 0 mT and 60 mT revealed equiaxed grains at the nugget center and columnar dendrite grains at the nugget edge in the welded joints. The Lorentz force accelerated the weld cooling rates after the addition of magnetic field, refining the weld grain structure. Tensile properties of the welded joints gradually improved with increasing the magnetic induction intensity from 0 mT to 60 mT, driven by the weld nugget size expansion and weld grain refinement. Overall, the present study indicated that the magnetic induction intensity of 60 mT resulted in the most favorable comprehensive mechanical properties of the investigated welded joints.

Allosterism in the adenosine A2A and cannabinoid CB2 heteromer.

Allosterism is a regulatory mechanism for GPCRs that can be attained by ligand-binding or protein-protein interactions with another GPCR. We have studied the influence of the dimer interface on the allosteric properties of the A2A receptor and CB2 receptor heteromer. We have evaluated cAMP production, phosphorylation of signal-regulated kinases (pERK1/2), label-free dynamic mass redistribution, β-arrestin 2 recruitment and bimolecular fluorescence complementation assays in the absence and presence of synthetic peptides that disrupt the formation of the heteromer. Molecular dynamic simulations provided converging evidence that the heteromeric interface influences the allosteric properties of the A2AR-CB2R heteromer. Apo A2AR blocks agonist-induced signalling of CB2R. The disruptive peptides, with the amino acid sequence of transmembrane (TM) 6 of A2AR or CB2R, facilitate CB2R activation, suggesting that A2AR allosterically prevents the outward movement of TM 6 of CB2R for G protein binding. Significantly, binding of the selective antagonist SCH 58261 to A2AR also facilitated agonist-induced activation of CB2R. It is proposed that the A2AR-CB2R heteromer contains distinct dimerization interfaces that govern its functional properties. The molecular interface between protomers of the A2AR-CB2R heteromer interconverted from TM 6 for apo or agonist-bound A2AR, blocking CB2R activation, to mainly the TM 1/7 interface for antagonist-bound A2AR, facilitating the independent opening of intracellular cavities for G protein binding. These novel results shed light on a different type of allosteric mechanism and extend the repertoire of GPCR heteromer signalling.

Structural basis of tethered agonism and G protein coupling of protease-activated receptors

Protease-activated receptors (PARs) are a unique group within the G protein-coupled receptor superfamily, orchestrating cellular responses to extracellular proteases via enzymatic cleavage, which triggers intracellular signaling pathways. Protease-activated receptor 1 (PAR1) is a key member of this family and is recognized as a critical pharmacological target for managing thrombotic disorders. In this study, we present cryo-electron microscopy structures of PAR1 in its activated state, induced by its natural tethered agonist (TA), in complex with two distinct downstream proteins, the Gq and Gi heterotrimers, respectively. The TA peptide is positioned within a surface pocket, prompting PAR1 activation through notable conformational shifts. Contrary to the typical receptor activation that involves the outward movement of transmembrane helix 6 (TM6), PAR1 activation is characterized by the simultaneous downward shift of TM6 and TM7, coupled with the rotation of a group of aromatic residues. This results in the displacement of an intracellular anion, creating space for downstream G protein binding. Our findings delineate the TA recognition pattern and highlight a distinct role of the second extracellular loop in forming β-sheets with TA within the PAR family, a feature not observed in other TA-activated receptors. Moreover, the nuanced differences in the interactions between intracellular loops 2/3 and the Gα subunit of different G proteins are crucial for determining the specificity of G protein coupling. These insights contribute to our understanding of the ligand binding and activation mechanisms of PARs, illuminating the basis for PAR1’s versatility in G protein coupling.

Molecular dynamics investigation of the influenza hemagglutinin conformational changes in acidic pH.

The surface protein hemagglutinin (HA) of the influenza virus plays a pivotal role in facilitating viral infection by binding to sialic acid receptors on host cells. Its conformational state is pH-sensitive, impacting its receptor-binding ability and evasion of the host immune response. In this study, we conducted extensive equilibrium microsecond-level all-atom molecular dynamics (MD) simulations of the HA protein to explore the influence of low pH on its conformational dynamics. Specifically, we investigated the impact of protonation on conserved histidine residues (His106 2 ) located in the hinge region of HA2. Our analysis encompassed comparisons between non-protonated (NP), partially protonated (1P, 2P), and fully-protonated (3P) conditions. Our findings reveal substantial pH-dependent conformational alterations in the HA protein, affecting its receptor-binding capability and immune evasion potential. Notably, the non-protonated form exhibits greater stability compared to protonated states. Conformational shifts in the central helices of HA2 involve outward movement, counterclockwise rotation of protonated helices, and fusion peptide release in protonated systems. Disruption of hydrogen bonds between the fusion peptide and central helices of HA2 drives this release. Moreover, HA1 separation is more likely in the fully-protonated system (3P) compared to non-protonated systems (NP), underscoring the influence of protonation. These insights shed light on influenza virus infection mechanisms and may inform the development of novel antiviral drugs targeting HA protein and pH-responsive drug delivery systems for influenza.

Structural basis for activation of somatostatin receptor 5 by cyclic neuropeptide agonists

Somatostatin receptor 5 (SSTR5) is an important G protein-coupled receptor and drug target for neuroendocrine tumors and pituitary disorders. This study presents two high-resolution cryogenicelectron microscope structures of the SSTR5-Gi complexes bound to the cyclic neuropeptide agonists, cortistatin-17 (CST17) and octreotide, with resolutions of 2.7 Å and 2.9 Å, respectively. The structures reveal that binding of these peptides causes rearrangement of a "hydrophobic lock", consisting of residues from transmembrane helices TM3 and TM6. This rearrangement triggers outward movement of TM6, enabling Gαi protein engagement and receptor activation. In addition to hydrophobic interactions, CST17 forms conserved polar contacts similar to somatostatin-14 binding to SSTR2, while further structural and functional analysis shows that extracellular loops differently recognize CST17 and octreotide. These insights elucidate agonist selectivity and activation mechanisms of SSTR5, providing valuable guidance for structure-based drug development targeting this therapeutically relevant receptor.

Large eddy simulation investigation of the effect of radiative heat transfer on the ignition progress in a model combustor

Radiation significantly influences turbulent combustion. This paper investigates the impact of radiative heat transfer on the ignition process in a multi-staged model combustor. The ignition process is simulated both without and with consideration of radiation. Large Eddy Simulations based on the Euler-Lagrange description of the liquid spray and the Dynamic Thickened Flame model coupled with a skeletal chemical reaction mechanism are employed. The Weighted Sum of Gray Gases method are employed to solve the spectral properties and the Discrete Ordinates method is employed to solve the radiative transfer equation. The results indicate that radiative heat transfer influences the flame structure during the ignition process. In the flame propagation phase, both the total heat transfer and the exit average temperature are higher, with the radiative heat transfer during ignition being less than 15% of the total heat transfer. During the kernel generation phase, radiative heat transfer leads to a 7.24% increase in the maximum temperature of the flame kernel, a 7.74% expansion of the flame surface area, and outward movement of the position of the maximum heat release rate. Additionally, the ignition delay time extends by 14.91%. In the flame propagation phase, the flame transfers heat to the mixed gas and droplets near the flame surface through radiation, promoting flame spread.

Study of Panel Zone Behavior in Interior Beam–Column Joints with Reduced Beam Section (RBS)

Based on the post-earthquake investigation of the Beiling and Hanshen earthquakes, many welded rigid beam–column joints were found to exhibit brittle failure. The failure modes of the joint region and the overall steel frame structure under the action of the earthquake need to be studied. The seismic performance of different types of weakened beam-end interior joints was investigated. The finite element method was verified by high-strength steel beam–column joint tests conducted by our research team. Finite element modeling of weakened steel beam flanges and weakened steel beam web joints was carried out based on the validated finite element modeling method. The joints were studied and analyzed using seismic parameters such as joint stress clouds, equivalent story shear–inter-story displacement ratio curves, panel zone bending moment–shear ratio curves, ductility, stiffness, and energy dissipation. The results of this study showed that honeycomb open hole-type joints exhibit a better deformation and energy dissipation capacity compared to open circular web hole-type joints. However, their load carrying capacity is reduced, which is mainly due to the larger area of the web openings. Additionally, double reduced beam section (DRBS) joints exhibit superior seismic performance and plastic hinge outward movement characteristics compared to single reduced beam section (RBS) joints. It was also found that the deformation and energy dissipation of DRBS joints and steel beam honeycomb hole-type joints are mainly borne by the beams, with the panel zone’s participation in energy dissipation accounting for a smaller proportion of the energy.

Microstructures and properties of 7075 aluminum alloy and CP780 steel resistance spot welded joint assisted by magnetic field

Joining steel and aluminum is vital for lightweight automobile but still challenging due to their different physical properties. Herein, resistance spot welding tests were performed on CP780 high-strength steel (thickness 1 mm) and 7075 aluminum alloy (thickness 1.5 mm) dissimilar metals under steady-state magnetic field. The influences of magnetic field (B = 40 mT) on the structure of welded joints, the phase composition/content of intermetallic compounds, and tensile properties of welded joints were analyzed under different welding current conditions (I = 9 kA,10 kA, 11 kA, and 12 kA). At the same welding current, the Lorentz force generated by the additional magnetic field promoted the outward circumferential movement of the molten metal in the weld along the horizontal surface , as well as increased the diameter of the Fe/Al contact interface in the weld nugget along the horizontal direction, conducive to the effective utilization of heat of the resistance spot welding. Except under (11 kA-0 mT) and (11 kA-40 mT), welded joints under other welding parameters displayed a few welding defects, such as incomplete fusion and shrinkage cavity formed at the cross-section of the welded joints. Therefore, the synergism between the magnetic field and appropriate welding current held important roles in the formation of welded joints without obvious welding defects. The intermetallic compounds of all the welds were mainly composed of (Fe, Si)Al2 and (Fe, Si)Al5. Meanwhile, the thickness and content of the intermetallic compounds layer reduced under a magnetic field at the same welding current, significantly improving the tensile properties of the welded joints. The comprehensive properties of welded joints were the best under 11 kA-40 mT, with an average shear force increase from 3.02 kN to 3.49 kN (15.56%) and an average displacement increase from 1.01 mm to 1.22 mm (20.79%). Overall, the proposed dissimilar aluminum/steel resistance spot welded joint assisted by magnetic field looks promising for lightweight automobile use.

Molecular Determinant Underlying Selective Coupling of Primary G-Protein by Class A GPCRs.

G-protein-coupled receptors (GPCRs) transmit downstream signals predominantly via G-protein pathways. However, the conformational basis of selective coupling of primary G-protein remains elusive. Histamine receptors H2R and H3R couple with Gs- or Gi-proteins respectively. Here, three cryo-EM structures of H2R-Gs and H3R-Gi complexes are presented at a global resolution of 2.6-2.7 Å. These structures reveal the unique binding pose for endogenous histamine in H3R, wherein the amino group interacts with E2065.46 of H3R instead of the conserved D1143.32 of other aminergic receptors. Furthermore, comparative analysis of the H2R-Gs and H3R-Gi complexes reveals that the structural geometry of TM5/TM6 determines the primary G-protein selectivity in histamine receptors. Machine learning (ML)-based structuromic profiling and functional analysis of class A GPCR-G-protein complexes illustrate that TM5 length, TM5 tilt, and TM6 outward movement are key determinants of the Gs and Gi/o selectivity among the whole Class A family. Collectively, the findings uncover the common structural geometry within class A GPCRs that determines the primary Gs- and Gi/o-coupling selectivity.

Investigation on the Mechanical Characteristics of the Excavation of a Double-Line Highway Tunnel Underpass Existing Railway Tunnel under the Influence of Dynamic and Static Load

Research on the excavation mechanical properties of underpass tunnels has already had certain results, but only a few of them consider the effects of dynamic and static loads on the excavation mechanical properties of underground tunnels at the same time; particularly, there is a lack of research investigating double-line highway tunnels with angled underpasses of existing railway tunnels. In this paper, based on the tunnel project of the new double-line Shiqian Highway Tunnel passing under the Hurong Railway with an oblique angle, based on the method of over-advance geological prediction and investigations into the palm face surrounding the rock, the rock degradation caused by dynamic and static loads is quantified using the perturbation system. Additionally, the mechanical parameters of the rock under the influence of dynamic and static load coupling in the influence area of the cross-tunneling project are determined using the Hoek–Brown criterion, and the mechanical characteristics of the excavation of a tunnel under the double-lane highway tunnel passing under the existing railroad are constructed with the mechanical characteristics of the double-lane highway tunnel, taking into consideration the influence of the dynamic and static load coupling in a three-dimensional model. The results show that, in line with the new tunnel rock movement law for the top of the arch sinking, the bottom plate bulging, the side wall outward movement, the height and width of the arch, and the bottom plate arch show an increase with the tunnel excavation, while the side wall rock displacement effect is smaller; the left and right line tunnel disturbed area of the rule of change is similar; the existing tunnel bottom plate displacement is larger than the top plate and the left and right side wall, under the influence of the excavation time step. Typical profile point displacement is mainly determined by the distance from the excavation surface; von Mises stress extremes are observed in the top plate and side walls of the existing tunnel, which occur in the tunnel structure, and there are unloading and pressure-bearing zones in the bottom plate; the new tunnel has the same rock disturbance angle under the four calculation conditions and, based on the displacement control criterion, the excavation method is preferred and the upper and lower step blasting excavation method is recommended.