Stress Direction Research Articles

Piezoelectricity and flexoelectricity in biological cells: the role of cell structure and organelles.

Living tissues experience various external forces on cells, influencing their behaviour, physiology, shape, gene expression, and destiny through interactions with their environment. Despite much research done in this area, challenges remain in our better understanding of the behaviour of the cell in response to external stimuli, including the arrangement, quantity, and shape of organelles within the cell. This study explores the electromechanical behaviour of biological cells, including organelles like microtubules, mitochondria, nuclei, and cell membranes. A two-dimensional bio-electromechanical model for two distinct cell structures has been developed to analyze the behavior of the biological cell to the external electrical and mechanical responses. The piezoelectric and flexoelectric effects have been included via multiphysics coupling for the biological cell. All the governing equations have been discretized and solved by the finite element method. It is found that the longitudinal stress is absent and only the transverse stress plays a crucial role when the mechanical load is imposed on the top side of the cell through compressive displacement. The impact of flexoelectricity is elucidated by introducing a new parameter called the maximum electric potential ratio ( ). It has been found that depends upon the orientation angle and shape of the microtubules. The magnitude of exhibit huge change when we change the shape and orientation of the organelles, which in some cases (boundary condition (BC)-3) can reach to three times of regular shape organelles. Further, the study reveals that the number of microtubules significantly impacts effective elastic and piezoelectric coefficients, affecting cell behavior based on structure, microtubule orientation, and mechanical stress direction. The insight obtained from the current study can assist in advancements in medical therapies such as tissue engineering and regenerative medicine.

Four-parameter punching theory for reinforced concrete flat slabs without transverse reinforcement

Despite extensive scientific research, the underlying physical principles in theoretical models for understanding punching behavior remain a concern. In this paper, a four-parameter punching theory for reinforced concrete flat slabs without transverse reinforcement has been introduced and validated. The kinematic behavior of the slab was characterized by three key parameters, i.e., critical shear crack inclination, slab rotation, and slab translation. Four distinct shear transfer effects from aggregate interlocking, concrete residual tensile stress, reinforcement dowel action, and the shear-compression ring, were considered and quantified using a novel algorithm based on these three parameters, and the fourth parameter, i.e., the direction of the minimum principal stress within the shear-compression ring. The punching capacity was subsequently determined by summing the contributions from these effects. This model was evaluated through extensive comparisons with experimental data, demonstrating that it accurately captures the influence of various parameters. Across the collected 260 test data, the average ratio of experimental to predicted punching capacity was 1.01, with a coefficient of variance of 0.11 and a coefficient of determination of 0.97. The average ratio, coefficient of variation, and coefficient of determination improved by 8 %, 21 %, and 1 %, compared to the optimal results from other design and theoretical models. The developed model can also assess all shear contributions, slab deformation, and critical shear crack inclination. It is ultimately confirmed that the proposed model can elucidate the physical phenomena and underlying mechanisms involved in punching behavior. Slab deformation primarily arises from flexural deformation, whereas shear forces are predominantly transmitted through the shear-compression ring. Punching failure is attributed to the failure of the shear-compression ring under tension-compression-compression triaxial stress.

A new three-dimensional strength criterion considering the transverse isotropy based on the α-Spatial Mobilized Plane

Natural geotechnical materials are affected by sedimentation and exhibit significant anisotropy. To study the transverse isotropy characteristics of soil, the influence of intermediate principal stress and loading direction must be considered. Currently, research on transverse isotropy primarily focuses on the modified stress space, which is cumbersome to apply in multi-yield surface constitutive models. To describe the three-dimensional mechanical properties of geomaterials in real stress space, the α-Spatial Mobilized Plane strength criterion is introduced. Then, combined with the structure tensor, the transverse isotropic three-dimensional strength criterion can account for the effect of the loading angle. Finally, the three-dimensional strengths of Fukakusa clay, unsaturated SP-SC soils, uncemented Monterey sands, Yamaguchi marble, San Francisco Bay mud, Toyoura sand, and Santa Monica Beach sand are predicted on the π-plane. The results show that the αmn-SMP criterion, in the context of transverse isotropy, can describe the three-dimensional mechanical properties reasonably, and it can provide an accurate strength criterion for geotechnical engineering practice.

Investigating the Effects and Mechanisms of Thermal–Vibration-Coupled Stress Relief Treatment on Residual Stress in SiC/Al Composites

Aluminum matrix composites reinforced with particles (PRAMCs) frequently develop considerable residual stresses post-quenching, which can negatively affect fatigue life and dimensional accuracy. Traditional stress relief methods for aluminum alloys are only partially effective. This study examined thermal stress relief (TSR), vibratory stress relief (VSR), and a combined thermal–vibratory stress relief (TVSR) approach for SiC/Al composites. All treatments proved successful in diminishing residual stresses, with the most significant reduction along the direction of peak dynamic stress. Additionally, this study analyzed micro-residual stresses via a macro–micro-residual stress finite element model to understand differences in stress relief outcomes. Optimizing the TVSR process could be key to more effectively reducing residual stresses in SiC/Al composites.

Particle morphology and principal stress direction dependent strength anisotropy through torsional shear testing

The major principal stress direction angle (ασ) experienced by granular soils varies widely in engineering, causing different strengths. However, how particle morphology affects the strength anisotropy behavior under different ασ remains unclear. To address this gap, this study performed drained hollow cylinder torsional shear tests under different ασ on six granular materials with distinct morphologies. Results highlight the significant dependence of peak strengths of granular materials on both particle morphology and ασ. Increasing particle shape irregularity and surface roughness leads to a considerable enhancement in peak strength, while this peak strength significantly degrades with increasing ασ. Materials with more irregular shapes were found to have a more pronounced strength anisotropy. Furthermore, the initial fabric of particle packings, derived from three-dimensional X-ray microtomography, was used to interpret microscopic mechanisms behind the morphology-dependent strength anisotropy. Irregular-shaped materials display broader preferred particle orientations and higher initial fabric anisotropy compared to relatively regular-shaped materials. This higher morphology-induced fabric anisotropy contributes to strength anisotropy, and a correlation was established for describing this trend. Additionally, an anisotropic failure criterion incorporating fabric anisotropy was developed to characterize the strength envelope for granular materials with diverse shapes.

Modelling of enhanced gas extraction in low permeability coal seam by controllable shock wave fracturing

The controlled shock wave (CSW) fracturing is an effective method for enhancing permeability of coal seam to promote gas extraction. Based on Fick’s law, Darcy’s law, the ideal gas law and the Langmuir equation, a damage-seepage-deformation coupling mathematical model of CSW fracturing in coal seam combined with the maximum tensile stress and the Mohr-Coulomb criterion is established. This model is implemented into COMSOL Multiphysics to simulate the coal seam CSW fracturing and subsequent gas extraction. When the shock wave and isotropic in-situ stress are applied on the borehole wall, the coal damage zone is an annular shape, and the permeability in the damage zone increases sharply. The CSW can effectively increase the efficiency of gas extraction and reduce the gas pressure and gas content in coal seam. With the increase of CSW action times, the damage in coal mass reaches a threshold and tends to be stable after several shocks. The damage area and the gas extraction efficiency are positively correlated with the shock intensity. Under the anisotropic ground stress, the larger diversity of the stress in different directions is, the more obvious damage extension in the fractured coal along the maximum stress direction is. Ground stress can inhibit the extension of cracks in the CSW fractured coal seam. This inhibition effect becomes more obvious with the increase of in-situ stress. Parameters are substantiated of controlled shock wave impact on the coal seam, which ensures increased methane extraction from low-permeability reservoirs, are substantiated.

Stress analysis and dislocation cluster generation in silicon crystal with artificial grain boundaries

We conducted a dislocation and stress analysis on various grain boundaries (GBs) using silicon ingots that contained artificial GBs to permit systematic comparison of experimental and analytical results. Through photoluminescence imaging, we found that the number of dislocation clusters generated around the 〈110〉-oriented GBs was significantly higher than those around the 〈100〉-oriented GBs. The stress analysis revealed that this difference is linked to the maximum shear stress around the GB. However, there were some GBs where dislocation cluster generation was not observed despite the presence of high shear stress. For most of these GBs, the direction of the maximum shear stress in the 12 slip system of silicon crystal was found to be oblique downward to the growth direction, which appears to inhibit dislocation propagation.

Crack propagation behavior and failure prediction of rocks with non-parallel conjugate flaws: Insights from the perspective of acoustic emission and DIC

Rock-like containing non-parallel conjugate flaws specimens (NPCFS) were prepared and uniaxial compression crack propagation tests were conducted employing acoustic emission (AE) and digital image correlation (DIC) techniques. The results show that: the angle of conjugate unilateral cracks increases, the average load-bearing capacity of the rock rises. Dominant frequencies from different conjugate defect angles exhibit distinct bimodal characteristics (low-frequency: 80–140 kHz, intermediate-frequency: 260–320 kHz). The concept of AE dominant frequency ratio β is proposed and introduced to quantify the strength of macro-scale failure of the specimens. The AE multiparameter is proposed to predict the failure load, and the mean value of failure load is predicted to be in the range of 86–93 % (failure load), the prediction interval of Ib value is in the range of 95–99 %, the prediction interval of critical slowing down variance value is in the range of 90–95 %, while the prediction interval of autocorrelation coefficient is in the range of 83–90 %. A favorable correlation was observed between AE events in NPCFS and surface deformations observed through DIC technology. Both ends of the conjugate flaw cannot propagate simultaneously; once one extends, the other ceases further expansion, forming a primary failure line that propagates towards the direction of the primary compressive stress.

Stability Characteristics of Natural Gas Hydrate Wellbores Based on Thermo-Hydro-Mech Modeling

During drilling operations, drilling fluids undergo heat exchange with hydrate-bearing formations. The intrusion of drilling fluids affects hydrate stability, leading to variations in stress fields around a wellbore and complex scenarios such as borehole collapse, significantly hindering the efficient development of natural gas hydrate resources. This study establishes a thermo-hydro-mech model for hydrate-bearing inclined wells based on linear thermoelastic porous media theory and an appropriately high inhibitive drilling fluid temperature. This research reveals that drilling should follow directions of minimum horizontal stress or perpendicular to maximum horizontal stress during drilling operations to control wellbore stability. Hydrate decomposition due to factors like drilling fluid pressure and temperature can rapidly reduce the strength of low-saturation formations, significantly increasing the risk of wellbore instability. Therefore, selecting appropriate highly inhibitive and low-temperature drilling fluids during drilling operations helps control hydrate decomposition and reduce fluid intrusion, thereby mitigating risks associated with wellbore instability.

Influence mechanism of the principal stress axis rotation effect on the propagation of blast-induced cracks under in-situ stress

In-situ stress plays a pivotal role in controlling both the propagation speed and trajectory of blast-induced cracks. Previous studies have primarily placed emphasis on the qualitative analysis of the propagation morphology of such cracks, but the principal stress axis rotation effect under static-dynamic coupling loading was ignored. Consequently, the mechanical mechanism of the propagation of blast-induced cracks has not been figured out yet. In this study, a combination of laboratory tests, theoretical analysis, and numerical simulations was employed to explore the influence mechanism of the principal stress axis rotation effect on the propagation of blast-induced cracks under in-situ stress. The results suggest that the hydrostatic pressure does not change the propagation trajectory of blast-induced cracks, but a higher hydrostatic pressure will inhibit both their propagation speed and length. In contrast, the deviatoric stress can change the propagation trajectory of blast-induced cracks, and a higher deviatoric stress makes it easier for blast-induced cracks to deflect to the maximum loading stress direction. Besides, the propagation of blast-induced cracks exhibits different features in different stages under in-situ stress. In the zone near the blast source, the dynamic stress is dominant; the maximum principal stress of the mass points is distributed in the radial direction; and blast-induced cracks expand mainly along the radial direction. On the contrary, in the zone far from the blast source, the static load is dominant; the maximum stress direction of the mass point alters to the maximum loading stress direction; and blast-induced cracks deflect from the radial direction to the maximum loading stress direction. Therefore, the propagation of blast-induced cracks under in-situ stress is a dynamic process in which dynamic and static stresses compete for crack initiation, and the changes in both stress value and principal stress direction are identified as the main reasons for the deflection of blast-induced cracks.

Vibration fatigue behavior and failure mechanism of Ni-based single-crystal film cooling hole structure under high temperature

Film cooling hole structures significantly influence vibration fatigue performance of Ni-based single crystal turbine blades. This study investigates the vibration fatigue behavior and failure mechanism of film cooling hole structure of Ni-based single crystal superalloy at high temperature by using the plate specimens with film cooling holes. The vibration fatigue cracks are all initiated at the edge of the film cooling hole on specimen surface, and the macroscopic crack path is a straight line path. At the microscopic scale, the crack path at 850 °C is a Zigzag path, but the crack path at 980 °C still shows a straight line path. The crack initiation of the specimen shows the oxidation crack nucleation in the stress concentration area under the coupling effect of high temperature and alternating stress. The macroscopic crack propagation direction at high temperature depends on the stress gradient direction of the resolved shear stress. At the microscopic scale, the crack propagation at 850 °C is the dislocation slip-climb mechanism, and the crack propagation at 980 °C more inclined to produce only the dislocation climb mechanism. The vibration fatigue cracks have the temperature dependence. The high temperature environment promotes the activation of slip system and the enhancement of dislocation mobility, the microscopic raft structure promotes the crack propagation along the γ phase with a large number of dislocations, the oxidation crack promotes the oxygen to enter the alloy matrix, which accelerates the Mode-I crack propagation.

Mechanism and controlling factors of mass transport complexes migration: A case study of the mass transport complexes in the taranaki deep water basin, New Zealand

Mass transport Complexes (MTCs) form significant sediment accumulations in continental slopes, hold key insights for natural hazard prediction and offshore oil exploration. This paper uses high-definition 3D seismic data to reconstruct the seismic geomorphology and sedimentary dynamics of MTCs, meticulously exploring the depositional systems of the Tanaraki Basin, New Zealand. It deciphers by kinematic notation, seismic faciess, quantifies megaclast morphological characteristics, in conjunction with the basal slope and channel structure development as the migration or kinematics of MTCs. Five seismic facies categories and dynamic traits—compression ridges, thrust faults, slides, grooves and slope terraces are distinguished in MTCs. Based on attributes maps and geomorphological interpretations, MTCs is segmented into four zones, showing combined effects of levée, basal slopes, and megaclast clusters on its migration. Lithological and topographical variations along these features modulate erosion properties and MTCs mobility, with base height shifts guiding local migration trajectories. The results of megaclast parameters in Zones 1 and 3 tune our understanding of stress patterns and directionality shifts, highlighting the complex dynamics at play. Notably, the differential motion triggered by levees instigates longitudinal shear zones. At critical migration disparities, MTCs fracture at these weak points, discharging pore pressure and filling fractures with fines, birthing “promontory” formations marked by low-amplitude fills. This work, therefore, establishes a groundbreaking migratory model that synthesizes the impacts of levees height, rock type variability, and megaclasts accumulation intensity, depicting a fragmented migration pattern. This study not only enriches our grasp of MTCs behavior in deep-water contexts but also furnishes a robust scientific foundation and predictive tool for gauging the hazards that MTCs may pose to underwater structures, thus carrying substantial theoretical and applied significance.

High temperature tensile creep behavior and microstructure evolution of Ti60 alloy rolled sheet

In this work, the high temperature tensile creep test of 2mm Ti60 alloy rolled sheet was carried out, and the creep behavior and microstructure evolution were studied. The initial microstructure of the 2mm Ti60 alloy rolled sheet is mainly composed of primary α phase and secondary α phase, and there are many dislocations and dynamic recrystallization (DRX) inside the rolled sheet. According to Norton-Bailey law, the creep stress exponent at 600 °C is calculated to be 3.6, and creep activation energy at 200MPa is calculated to be 286.4kJ/mol. It implies that the creep mechanism of the rolled sheet includes dislocation slip and dislocation climb. The initial Ti60 alloy rolled sheet has the {0001}<10-10>α texture. Stretching along the RD makes the texture direction gradually change from B-type (<0001>//ND) to T-type (<0001>//TD). Whether it is the B-type texture or T-type texture, the (0001) plane of the α phase always exhibits a basal texture state parallel to the tensile stress direction, contributing a good tensile creep property of this alloy sheet.

Calculation method and evolution rule of the strain energy density of sandstone under true triaxial compression

Deep rock masses are typically in complex stress states, and research on the evolution of their strain energy density is of highly important for understanding their failure characteristics. In this work, a true triaxial stress‒balanced unloading test is designed to analyze the ud and ue evolution of sandstone under true triaxial compression conditions. The study results indicate that as σ1 increases, the elastic strain decreases in the σ2 and σ3 directions, whereas the residual strain progressively increases, and the magnitude of decrease in elastic strain exceeds the magnitude of increase in residual strain. Throughout the loading process of σ1, ue progressively decreases in the σ2 and σ3 directions, whereas ud gradually increases, and the magnitude of decrease in ue surpasses the magnitude of increase in ud. The ud and ue of sandstone under different stress levels were calculated via true triaxial stress‒balanced unloading tests, and the evolution of ud and ue in the three principal stress directions and the overall strain energy density of sandstone followed a linear energy storage law. On the basis of this law and the true triaxial stress‒balanced unloading test, a new method for calculating the true triaxial ud and ue was proposed. A study on the σ1 unloading stress path revealed that the σ1 unloading stress path significantly affects the storage and dissipation of the strain energy density in the three principal stress directions of sandstone. On the basis of the research results, the criteria for determining rockbursts were discussed.

Crust and Mantle Flow From Central Tibetan Plateau to the Indo‐Burma Subduction Zone

AbstractThe extremely oblique Indo‐Burma subduction zone exhibits dextral strike‐slip faulting along the Sagaing, Kabaw, and Churachandpur‐Mao Faults as well as east‐west shortening between the Sagaing Fault and Bengal Basin. Through regional stress analysis, considering areas from central Tibet, around the eastern Himalaya Syntaxis, to Burma, it has been determined that the principal compressive stress directions align with the principal strain rates. The northeast‐southwest oriented compressive stress direction from the western Shan Plateau continues into Burma. Notably, P axes align with the topographic gradients, and T axes are sub‐parallel to the topographic contours in the Shan Plateau region south of 27°N. These stress patterns are consistent with a gravitational potential energy induced crustal and mantle flow. The alignment of the fast shear wave with the maximum strain rate and the colinear NW‐SE to E‐W fast direction of the SKS wave and T axis determined from focal mechanisms in the Shan Plateau suggest that the mantle lithosphere deforms in concert with the crust. We suggest crust and mantle flow south of the Red River Fault has resulted in widening of the lithosphere in the Shan Plateau in an east‐west direction. Therefore, the Sagaing Fault has bowed approximately 50–100 km westward if we assume that the Sagaing Fault was originally straight. Our results of regional stress inversion are consistent with late Miocene to present E‐W shortening in the Indo‐Burma subduction zone resulting from the release of gravitational potential energy from the central Tibetan Plateau.

Mechanical mechanism of dip effect on bearing capacity of the pillar strength

Abstract The dip effect on pillar strength in underground ore-body mining is well established, but the variation in stress path (magnitude and direction of stress) due to changing inclination angles requires further study. Using elasticity theory, the Euclidean mean stress tensor characterizes the stress state in pillar zones. Numerical simulations provided the second-order tensor of peak stress for each pillar unit. Through tensor statistical analysis, the Euclidean mean stress tensor matrix was calculated, and its eigenvalues and eigenvectors, representing the magnitude and direction of the principal stress, were derived. This analysis explained the intrinsic dip effect on pillar strength through principal stress characteristics. Finally, the pillar strength envelope function for varying width-height ratios at any dip angle was obtained using the random gradient descent algorithm. Results indicate that in the peak stress state, the average principal stress directions of the pillar change with orebody dip angle, affecting the stress path. The average principal stress increases with pillar size due to increased constraints. These findings offer theoretical insights for pillar design and stability analysis.

Identifying the high potential zones for hydraulic fracture propagation / Eastern Baghdad field

For a reservoir with high storage capacity and low ability to produce, the serious problem is the sharp reduction in the recorded well productivity within a short period. One solution to this problem is to create hydraulic fractures that increase formation permeability and keep its production at high rates for a sufficient time. The field under study is the East Baghdad oil field of three formations: Saadi, Tanuma, and Khasib. Knowing the geomechanical behavior of these reservoirs has a critical effect on the success of hydraulic fracturing operations. In this study, rock stress magnitude and direction, rock elasticity, rock strength to fracturing initiation, and all these parameters in addition to petrophysical properties will be used to identify whether the hydraulic fracturing operation could be successful or not. An integrated modeling of the studied reservoir is an essential step including 1-D geomechanical evaluation of many formations in order to choose the perfect layer to create hydraulic fracture. Then, a 3-D distribution of geomechanical properties and petrophysical properties was presented to make a perfect selection of these properties. The geomechanical evaluation of the reservoirs under study is supported by experimental evaluation of core samples including Energy Dispersive X-ray spectroscopy (EDS), Scanning Electron Microscopic (SEM) image, and thin section (TS) image. The results show that a reduction in the calculated geomechanical properties in terms of Poisson ratio young modulus and compressive strength are favorable for candidate layer selection. Among the studies of rock mechanical properties, it is also noticed that unconfined compressive strength is a crucial parameter for best layer selection. The suitable depths for fracturing jobs are given in detail in this study using brief data collected from four wells.

Propagation prediction of asymmetrically originated fractures by use of displacement discontinuity method

In existing fracture propagation simulation studies, the fracture propagation simulation is based on the assumption that the fracture originates symmetrically with respect to the wellbore. However, the drilling treatments can induce stress reorientation near the wellbore, resulting in asymmetrically originated fractures, which is different from the assumption of existing studies. In such cases, it can be difficult to predict the fracture geometries. In this work, the authors propose a fracture propagation model to simulate the propagation of asymmetrically originated fractures with the displacement discontinuity method. With the aid of the proposed model, the authors investigate the impact of the redistribution of stress field on the propagation of asymmetrically originated fractures and conduct a comprehensive study to investigate the effects of various geological and fluid parameters on the propagation of asymmetrically originated fractures. The results show that the redistribution of the stress field renders the newly generated fracture segments to deviate from the initial originations so that although the initial fracture origination is asymmetric, the asymmetrically originated fractures rapidly propagate along an approximately symmetrical path and propagate parallel to the direction of maximum principal stress as it goes away from the wellbore. The closer the two wings of the fracture are to the symmetric origin, the faster it is for the change of propagation direction to the direction of the maximum principal stress. A large principal stress difference tends to cause asymmetrically originated fractures to quickly deviate from the initial originations and propagate parallel to the direction of maximum principal stress. As the fluid power law index decreases, the fluid viscosity is significantly reduced due to the effect of shear thinning, causing the asymmetrically originated fractures to propagate parallel to the direction of maximum principal stress. The fluid leak-off coefficient only influences the fracture length and width, whereas its influence on the propagation trajectory can be slight.

Potential formational scenarios of the mud volcanoes in the Zhurong landing area in Utopia Planitia, observed by Tianwen-1

The widely distributed pitted cones in Utopia Planitia have several explanations, and they have been interpreted as mud volcanoes in the Zhurong landing area. The morphology and distribution characteristics of mud volcano cones can serve as indicators of stress direction and can also be used to calculate potential depth for mud sources. This information may assist in elucidating the potential formational scenarios of the mud volcanoes, which is of great significance to study the tectonic evolution in Utopia Planitia and possible water ice depths. The digital orthophoto map (DOM) and the digital elevation model (DEM) with spatial resolutions of 0.7 m and 3 m obtained by High Resolution Imaging Camera (HiRIC) from Tianwen-1 show that the mud volcanoes are distributed as both isolated cones and clustered cones in the Zhurong landing area. The age of the mud volcanoes is limited to the middle to late Amazonian (∼2.0 Ga - 400 Ma) based on the crater size-frequency distribution (CSFD); the depth range of the mud source is estimated to be ∼0.6–7.2 km by self-similar clustering analysis. The orientations of the aligned cones and the elongated mud vents indicate that the maximum horizontal stress (SH) directions during the formation of the mud volcanoes in the landing area are in the direction of N67°E, which is in good agreement with the orientations of the nearby troughs, suggesting that the formation of the mud volcanoes in the landing area may have been controlled by the fracturing of the lower part of the troughs. These features, compared with those reported in previous study of mud volcanism/cone morphology on Mars, collectively suggest that the mud volcanoes in the landing area may have formed in a geological scenario under conditions of volcanic destabilization. Further, the formation of the mud volcanoes, with the analysis of the SH, may have been influenced by both basin subsidence and the volcanism in the Elysium region. This study provides a new example of Martian mud volcano geologic formation scenarios, offers the feasibility of using the SH to analyze Martian mud volcano formation, and hints at active geologic phenomena on Mars during the Amazonian period.

Effects of overconsolidation on seismic rock physics — A comparative study between unconsolidated sands and weakly cemented sandstone

In seismic rock physics, models typically assume rocks are normally consolidated, often neglecting the effects of overconsolidation. Recent studies reveal that overconsolidated sands, resulting from stress release, show different physical property variations than normally consolidated sands. However, similar research is lacking for weakly cemented sandstones, a common reservoir analog. This study aims to systematically compare the effects of overconsolidation and stress direction on unconsolidated sandstones and weakly cemented sandstones. It also assesses the impact of overconsolidation on seismic interpretation, monitoring, and rock physics modeling applied to the two types of rocks. Experimental measurements of porosity, P-wave, and S-wave velocities were collected under different stress paths between loading and unloading. For weakly cemented sandstone, well-log data from the Norwegian Sea and Barents Sea were compared with experimental data. Analyses focused on the velocity-porosity relationship, VP/VS ratio vs. AI, and VP/VS ratio vs. effective stress.