Post-peak Strain Softening Research Articles

Research on the effects of heating and cooling processes on the mechanical properties of yellow rust granite

Geological hazards caused by high-temperature rocks cooling down after encountering water are closely related to underground mining and tunneling projects. To fully understand the impact of temperature changes on the mechanical properties of rocks, yellow rust granite samples were subjected to heating-natural cooling and heating-water cooling cycles to experimentally study the effects of these processes on the mechanical properties of the samples. The mechanism of the heating-cooling process on the macromechanical properties of the rock was discussed. Based on the Drucker-Prager criterion and Weibull distribution function, a damage variable correction factor was introduced to reflect the post-peak strain softening characteristics, and a thermo-mechanical coupled damage constitutive model of the granite was established. The results showed that in the natural cooling mode, the mechanical properties deteriorate significantly when the temperature exceeded 600 ​°C, and the failure mode changed from brittle failure to ductile failure. In the water cooling mode, the peak strength and deformation modulus increased at temperatures below 400 ​°C with an increase in the cycle number, while at 600 ​°C, the peak strength and elastic modulus notably decreased. The peak strain increased with the increase of the cycle number and temperature at all temperatures, and the failure mode of the granite tended to change from tensile failure mode to shear failure mode. The experimental results were used to validate the damage constitutive model. The shape parameter r and scale parameter S in the Weibull distribution function of the model were used as indicators to reflect the brittleness degree and peak strength. This study helps to understand the behavior of rocks in high-temperature environments, in order to prevent and mitigate potential geological hazards.

FRP bar-reinforced ultra-high-performance concrete plates with a grouting sleeve connection: Development and flexural behavior

Fiber reinforced polymer (FRP) bars have been proposed for use in ultra-high performance concrete (UHPC) as the reinforcement to mitigate/avoid the post-peak strain softening of UHPC under tension and to reduce the fiber dosage used in UHPC. The so-formed FRP-reinforced UHPC plates could be adopted for both structural strengthening and constructing novel structural elements. In this paper, a novel connection based on FRP bars and steel grouting sleeves has been developed for prefabrication construction of FRP bar-reinforced UHPC structures. Flexural tests were conducted to gain understandings of the effects of the connection mode (the staggered connection and the horse tooth connection) and reinforcing fiber type (polyethylene (PE) fibers and steel fibers) in the UHPC on the flexural behavior of connected FRP bar-reinforced-UHPC composite plates. The test results revealed that the proposed connection system is reliable since the composite plates always failed outside the connection zone, and most of the crack opening displacements at the interface of the connection are smaller than 0.2 mm at ultimate. The connection mode and the fiber type had little influence on the first cracking load and the initial bending stiffness of the FRP bar-reinforced UHPC plates, while the horse tooth connection led to a better ductility of the composites plates than the staggered connection mode. At given tolerable deflection of 1/200 span (about 5 mm), the longitudinal strains developed in the CFRP bars were about 2000 με for all specimens.

Effect of Viscoplasticity on Localization in Saturated Clays and Plastic Silts

A numerical study is presented of the effects of viscoplasticity on localization processes in sensitive, saturated clays and plastic silts. Numerical simulations of laboratory specimens of sensitive, viscoplastic soil subjected to monotonic, undrained, direct simple shear loading were performed using a viscoplastic constitutive model. Parametric analyses evaluated the effects of soil sensitivity, postpeak strain-softening rate, and strain rate dependency, as well as specimen size, mesh discretization, and loading rate. The numerical results showed that the global strain at which a localization forms primarily depends on the strain rate dependency of the soil’s shearing resistance relative to its rate of postpeak strain softening. A regression model is subsequently presented that relates the global strain at the onset of localization to the soil’s strain rate dependency and postpeak strain-softening rate. The results indicate that the inclusion of reasonable levels of viscoplasticity significantly increases the strain that can develop before a localization develops in clays and plastic silts with modest strain-softening rates. The consistency of the numerical results with available laboratory observations is discussed. Implications for practice and future research needs are discussed.

Comparative study on the impact-induced microstructural damage in concrete using X-ray computed micro-tomography

To better understand the failure behavior of cementitious materials during dynamic loading, the microstructural damage initiation and development in an ultra-high-performance concrete (UHPC) and a special type of conventional concrete (CC) with an average aggregate size of only 2–3 mm are comparatively studied using the X-ray computed micro-tomography (micro-CT) technique. Quantitative measurements of reconstructed 3D crack morphology are performed on specimens recovered from controlled intermittent dynamic loading experiments, with different extents of damage introduced through a modified Kolsky bar apparatus. By correlating the loading history of the recovered specimen with the crack development within the bulk, a quantitative relationship between several crack parameters (e.g., crack volume, crack surface area, and void-crack interaction) and the increasing plastic strain are obtained. The results demonstrate the formation of cracks prior to the peak stress and reveal a fundamental difference in crack development between the two different concretes being investigated. Further evaluation between the measured crack parameters and the calculated constitutive damage variables indicates that compared to UHPC, CC is capable of sustaining considerable post-peak strain softening and its residual mechanical properties (strength and stiffness) are more susceptible to crack development in the bulk material. Comparative analyses on the size distribution of different void subsets also reveal the inherent connection between the pre-existing large-size voids in the bulk material and the loading-induced crack network. These experimental results provide a comprehensive view on the microstructural damage evolution mechanisms for these two concrete materials under dynamic loading conditions and may shed light on the development of future multi-scale concrete damage models.

Study on the Failure Mechanism and Permeability Characteristics of Gas Containing Sandstone Intercalated Coal.

The deformation failure mechanism and permeability characteristics of loaded coal sandstone samples under triaxial stress loading were analyzed based on the experimental platform of the coal-rock fluid solid coupling triaxial servo system. The results show that the stress–strain curve of coal intercalated sandstone can be divided into five stages: compaction closure, elastic deformation, stable fracture expansion, unstable fracture expansion, and post-peak strain softening. With the increase of confining pressure, the peak strength and residual strength of the sample increase linearly with the confining pressure. The permeability of the sample decreases slowly with the increase of axial strain, increases rapidly after reaching the stage of unstable fracture propagation, and changes in “V” shape. The relationship between initial permeability and confining pressure can be fitted with exponential function. Based on the fracture volumetric strain model, the progressive failure mechanism of damage expansion of coal mixed sandstone is discussed. The fracture volume strain of each sample under different stress states is given, and the failure mode and crack distribution characteristics of the sample are obtained. The research results can provide reference for reasonable, safe, and efficient coal mining and gas disaster control.

Investigation of Deep Shaft-Surrounding Rock Support Technology Based on a Post-Peak Strain-Softening Model of Rock Mass

To control the large deformation that occurs in deep shaft-surrounding rock, the post-peak strain-softening characteristics of deep jointed rock mass are discussed in detail. An equivalent post-peak strain-softening model of jointed rock mass is established based on continuum theory and the geological strength index surrounding rock grading system, and numerical simulations are performed using FLAC3D software. The convergence-constraint method is used to analyze the rock support structure interaction mechanism. A composiste support technique is proposed in combination with actual field breakage conditions. During the initial support stage, high-strength anchors are used to release the rock stress, and high-stiffness secondary support is provided by well rings and poured concrete. This support technology is applied in the accessory well of a coal mine in Niaoshan, Heilongjiang, China. The stability of the surrounding rock support structure is calculated and analyzed by comparing the ideal elastic-plastic model and equivalent jointed rock mass strain-softening model. The results show that a support structure designed based on the ideal elastic-plastic model cannot meet the stability requirements of the surrounding rock and that radial deformation of the surrounding rock reaches 300 mm. The support structure designed based on the equivalent joint strain-softening model has a convergence rate of surrounding rock deformation of less than 1 mm/d after 35 days of application. The surrounding rock deformation is finally controlled at 140 mm, indicating successful application of the support technology.

Modeling delamination migration in composite laminates using an enhanced semi-discrete damage model (eSD2M)

This paper presents an extension of the semi-discrete damage model (SD2M) (Nguyen and Waas, 2020a,b), implemented using the finite element (FE) method, to capture the interaction of intra-laminar matrix cracks and inter-laminar failure (delamination migration). In the enhanced semi-discrete damage model (eSD2M), the plies are modeled with continuum finite elements and the interlayers are represented with cohesive elements. A meshing strategy is presented to create compatible meshes for interlayers in order to capture a proper load transfer between the laminae and the interfaces. The material pre-peak non-linearity of the composite is modeled with Schapery theory (ST), the post-peak strain softening is captured with the crack band (CB) method including a mixed-mode law for matrix failure. For the cohesive behavior of the interfaces, a novel mixed-mode traction–separation law is proposed. The model is validated on the basis of a ply-scaled quasi-isotropic open-hole tensile (OHT) laminate that shows a delamination-dominated failure. The eSD2M model is able to capture major matrix cracks at the hole including 0° splitting as well as distributed matrix cracks and free edge cracking. The present model is capable of predicting the delamination migration mechanism with an accurate peak load and the total failure due to fiber tensile rupture in a realistic manner.

Investigation of the influence of gas fracturing on fracturing characteristics of coal mass and gas extraction efficiency based on a multi-physical field model

Coal seam gas recovery is a critical way to achieve clean energy development and reduce greenhouse gas emissions. Gas fracturing, as a necessary and advantageous stimulation measure, can effectively achieve gas extraction from deep coal seams and ensure safe production in deep coal mines. In this study, a hydro-mechanical coupling model is established to analyze the damage characteristics of coal seams during gas fracturing. The model focuses on three aspects: (a). the fracture criterion of type-I fracture under the action of multiple stress states in the fracturing process; (b). the characteristics of post-peak strain softening of coal and its influence on coal permeability; (c). the influence of non-uniform stress state on directional compression deformation and directional permeability of coal. The difference between gas fracturing (nitrogen, CO2) and hydraulic fracturing is studied based on this coupling model. The development of fractures in coal seam gas reservoirs after gas fracturing is investigated, and the influences of the coal parameters of the gas extraction process after fracturing are determined. Results show that because of the different compression coefficients, viscosities of water and gas and the slippage effect, there are obvious differences in the fracturing pressure of gas and water. Under the same parameters, the hydraulic fracturing method needs larger fracture initiation pressure than the gas fracturing method (nitrogen, CO2). For two kinds of media (nitrogen, CO2) in gas fracturing, in addition to the parameter difference of gas itself, the adsorption of CO2 is also the main factor affecting the fracturing pressure. The increase of coal permeability and Biot's coefficient will reduce the fracture initiation pressure, and the increase of confining pressure will increase the fracture initiation pressure.

Study on Damage Constitutive Model of High-Concentration Cemented Backfill in Coal Mine

In order to construct the damage constitutive model (DCM) of high-concentration cemented backfill (HCCB) in coal mine, the generalized Hoek-Brown strength criterion was used as the failure criterion. For the difference of theoretical derivation of constitutive relation, a new DCM based on residual strength was proposed. Combined with the conventional triaxial compression test, the correctness and rationality of the DCM were verified. The damage evolution characteristics of HCCB were analyzed, and the physical meaning of model parameters was clarified. The results show that (a) the theoretical curves of stress-strain relation are in good agreement with its experimental curves, which means DCM can simulate the deformation and failure process of HCCB. (b) The damage evolution curve of HCCB is S -shaped. To some extent, the confining pressure can inhibit the development of damage. (c) The parameter F 0 reflects the position of the peak point of the DCM, and parameter n is the slope of the straight line segment in the postpeak strain softening stage, which are, respectively, used to characterize the strength level and brittleness of HCCB. The establishment of DCM of HCCB is helpful to reveal its deformation and failure mechanism and provides theoretical basis for its strength design.

Experimental and Numerical Studies on the Direct Shear Behavior of Sand-RCA (Recycled Concrete Aggregates) Mixtures with Different Contents of RCA.

Recycled concrete aggregate (RCA) is a typical construction and demolition (C&D) material generated in civil engineering activities and has been widely used as the coarse-grained filler added to sand for roadbed fillings. The effect of RCA content on the mechanical behavior of sand–RCA mixtures is complicated and still not fully understood. To explore the effect of RCA content on the macroscale and microscopic behavior of the sand–RCA mixtures with various RCA contents, laboratory direct shear tests and numerical simulations using the 3D discrete element method were performed. Experimental direct shear tests on sand–RCA mixtures with different contents of RCA were first carried out. Numerical direct shear models were then established to represent the experimental results. The particle shape effect was also considered using a new realistic shape modeling method to model the RCA particles. Good agreement was observed between the DEM simulation and experimental results, verifying the ability of the numerical direct shear models to represent the direct shear behavior of sand–RCA mixtures. The macroscopic responses of both experimental and numerical tests showed that all samples presented an initial hardening followed by a post-peak strain softening. The peak-state friction angles increased with the RCA content for samples under the same vertical stress. The effect of RCA content on the microscopic behavior based on DEM simulation was also found. The microscopic properties of RCA–sand mixtures, such as coordination numbers, PDFs and contact force transformation features, were analyzed and related to the macroscopic results.

Evaluation Method of Production Pressure Differential in Deep Carbonate Reservoirs: A Case Study in Tarim Basin, Northwest China

Deep and even ultra-deep petroleum resources play a gradually increasing and important role with the worldwide continuous advancement of oil and gas exploration and development. In China, the deep carbonate reservoirs in the Tarim Basin are regarded as the key development areas due to their huge reserves. However, due to the unreasonable design of production pressure differential, some production wells suffered from severe borehole collapse and tubing blockage. Therefore, the main purpose of this paper is to optimize a more practical method for predicting the critical production pressure differential. The commonly used analytical methods with different failure criteria for predicting production pressure differential were summarized. Furthermore, their advantages and disadvantages were analyzed. A new numerical model is established based on the finite element theory in order to make the prediction of production pressure differential more accurate. Additionally, both analytical and numerical methods were applied to evaluating the production pressure differential of deep carbonate reservoirs in the Tarim Basin, and the results were discussed compared with field data. In addition, a series of laboratory tests, including porosity and permeability measurements, electron microscope scanning, XRD for mineral analysis, uniaxial and triaxial compressive strength test, etc., were carried out by using the collected carbonate cores from formations deeper than 7000 m to obtain the input parameters of the simulation such as the rock properties. The experimental results showed that the carbonate rocks exhibited a remarkable brittleness and post-peak strain softening. The calculation results revealed that the Mogi-Coulomb criterion is slightly conservative; however, it is more suitable than other criteria to evaluate pressure differential. Furthermore, it has been confirmed by the field data that the finite element numerical method can not only reveal the instability mechanism of the wellbore but also predict the critical production pressure differential accurately. Unfortunately, the on-site operators sometimes require a more convenient way, such as an analytical method, to figure out the pressure differential, even though the evaluation of the numerical method is more accurate. Therefore, the discussion in this paper can provide a basis for the operators to determine the production pressure differential flexibly.

Analysis on Characteristics of Surrounding Rocks of Roadway and Bearing Structure Based on Stress Regulation

To address the prominent status of great deformation and difficult maintenance of the roadway under high stresses, this study investigated the mechanical characteristics of surrounding rocks and bearing structural stability in a roadway under adjustment and redistribution of stresses through theoretical analysis, numerical simulation, and engineering field test. Stability forms of the bearing structure of roadway surrounding rocks were analyzed by using the axis-changing theory from the perspectives of surrounding rock, mechanical properties of roadways, surrounding rock stress distribution, and mechanical mechanism of the bearing structure. It is suggested that the surrounding rock stress distribution state is improved and the bearing structure is optimized through unloading and reinforcement construction. A mechanical model of roadway excavation was constructed to analyze the influences of excavation spatial effect on the stress releasing and bearing structure of surrounding rocks. A rock postpeak strain softening and dilatation model was introduced to investigate the mechanical characteristics of the surrounding rock mass in the rupture residual zone and plastic softening zone in a roadway. Moreover, we analyzed the influences of unloading and reinforcement construction on the stress path and mechanical characteristics of the rock unit model, which disclosed the adjustment mechanism of the bearing structure of surrounding rocks by the failure development status of rocks. A numerical simulation on the distribution of surrounding rock stress fields and adjustment features of the bearing structure after roadway excavation and unloading and reinforcement construction was carried out by using the FLAC3D program. Results demonstrate that the unloading construction optimizes the axial ratio of spatial excavation in a roadway and the reinforcement zones on both sides are the supporting zones of the bearing structure. Moreover, the ratio between the distance from two side peaks to the roadway sides and the distance from the roof and floor peaks to the excavation space is equal to the coefficient of horizontal pressure. In other words, the final collapse failure mode of surrounding rock is that the long axis of the excavation unloading space points to the same direction with the maximum principal stress of the primary rock. Reinforcement forces the surrounding rocks to form a “Ω-shaped” bearing structure, which is in favor of the long-term maintenance of the roadway.

Mechanical Strength Characterization of Plastic Fiber Reinforced Cement Concrete Composites

The reinforcing efficiency of plastic fibers obtained from shredded plastic waste was tested in plain concrete mixes and experimentally verified in this study. Plastic fibers up to 0.15% Vf were added to the design concrete mix to assess the fiber effectiveness in terms of improved load carrying capability of various plastic fiber incorporated concrete composites. The effects of plastic fibers distributed homogenously in the entire depth of concrete and confined in the tension zone were evaluated in flexural bending properties. Mechanical strength properties were evaluated for two different types of concrete containing (i) plastic fibers added homogenously throughout the entire depth of concrete and (ii) the plastic fibers confined in the tension zone only. Flexural bending parameters such as toughness, residual strength, crack width, post-peak drop load resistance, and fiber performance index of various plastic fiber substituted concrete mixes were tested in compressive and flexural bending to assess the fiber reinforcing efficiency. Test results indicated that the plastic fibers added in tension zone confinement exhibited higher flexural strength (5.26 N/mm2) improvements compared to homogeneously distributed concrete systems. Flexural bending characteristics in terms of absolute toughness and post peak strain softening were found to be appreciably higher (132%) in tension zone confined plastic fiber concretes compared to homogeneous fiber concrete systems.

Investigations of the effects of particle morphology on granular material behaviors using a multi-sphere approach

This article studies the influences of particle morphology on the behaviors of granular materials at both macroscopic and microscopic levels based on the discrete element method (DEM). A set of numerical tests under drained triaxial compression was performed by controlling two morphological descriptors, i.e. ratio of the smallest to the largest pebble diameter, ξ , and the maximum pebble–pebble intersection angle, β . These descriptors are vital in generating particle geometry and surface textures. It was found that the stress responses of all assemblies exhibited similar behavior and showed post-peak strain-softening. The normalized stress ratio and volumetric strains flatten off and tended to reach a steady value after an axial strain of 40%. While the friction angles at peak state varied with different morphological descriptors, the friction angles at critical state showed no significant variation. Moreover, evolution of the average coordination numbers showed a dramatic exponential decay until an axial strain of about 15% after which it stabilized and was unaffected by further increase of axial strain. In addition, stress ratio q / p and strong fabric parameter ϕ d s / ϕ m s were found to follow an approximately linear relationship for each assembly. These findings emphasized the significance of the influences of particle morphology on the macroscopic and microscopic responses of granular materials.

A generic computational model for three-dimensional fracture and fragmentation problems of quasi-brittle materials

Fracture and fragmentation in three dimensions are of great importance to understand the mechanical behaviour of quasi-brittle materials in failure stress states. In this paper, a generic computational model has been developed in an in-house C/C++ code using the combined finite-discrete element method, which is capable of modelling the entire three-dimensional fracturing process, including pre-peak hardening deformation, post-peak strain softening, transition from continuum to discontinuum, and explicit interaction between discrete fragments. The computational model is validated by Brazilian tests and polyaxial compression tests, and a realistic multi-layer rock model in an in situ stress condition is presented as an application example. The results show that the computational model can capture both continuum and discontinuum behaviour and therefore it provides an ideal numerical tool for fracture and fragmentation problems.

A study on mechanical properties and damage model of rock subjected to freeze-thaw cycles and confining pressure

red sandstone was tested in the freeze-thaw cycle under open and saturated conditions, and the mechanical properties of samples after different freeze-thaw cycles (0, 5, 10, 20, and 40 freeze-thaw cycles) were tested under the four kinds of confining pressures (0 MPa, 2 MPa, 4 MPa, 6 MPa). The whole process characteristics of deformation and failure of red sandstone were analyzed, and the effects of freeze-thaw cycles and confining pressure on red sandstone mechanical properties were studied. According to the characteristics of rock material non-uniformity and randomness, the effect of freeze-thaw and load coupling effect on the total damage was quantitatively expressed, and established a damage model can reflect the whole process of rock deformation. The theoretical expression of model parameters were derived by using the multivariate function to obtain total differential method, and the damage mechanical properties of rock were analyzed. The results has shown that: With the increase of the freeze-thaw cycles and confining pressure, the compressibility of rock is continuously enhanced, the peak strain is gradually increasing, the plastic yielding section is becoming more and more obvious, the post-peak stress reduction rate slows down, and the failure mode is transformed from brittleness to ductility. Meanwhile, the elastic modulus, peak stress and residual strength increase with the increase of confining pressure, and decrease with the increase of freeze-thaw cycles. The damage model reflects the process of deformation and failure of frozen-thawed rock under the action of load, especially the characteristics of post-peak strain softening and residual strength. The rock total damage evolution path reflects that the meso-mechanical response was consistent with the macro-deformation and failure characteristics, and the nonlinear influence characteristics of freeze-thaw and load on the rock total damage propagation are described. Furtherly, the deformation failure of rock is revealed by the mechanical damage mechanism.

Comparative study on sanding characteristics between weakly consolidated sandstones and unconsolidated sandstones

Sand production is a common phenomenon during the extrusion of hydrocarbons, which reduces production efficiency and brings about safety problems. A detailed knowledge of sanding process is essential for targeted sand control. This paper aims at investigating the sanding characteristics of weakly consolidated sandstones and unconsolidated sandstones by comparative methods. We conducted sanding experiments on artificial cores of different consolidation degrees and performed numerical studies based on explicit finite element method. We found that hole failure mode, sanding form and the particle size distribution of the produced sand are three typical features distinguishing sand production of weakly consolidated sandstones from that of the unconsolidated ones. Macroscopically, the weakly consolidated sandstones tended to develop localized failure with mainly rock pieces produced while the unconsolidated one failed uniformly with almost loose grains produced. On the particle scale, the sand produced by weakly consolidated sandstone showed better uniformity and lower fine particle content relative to the original sample while the unconsolidated sandstone produced sand with practically the same size as the original core. We suggest that cohesion is the dominant factor that affects sanding characteristics and post-peak strain softening is critical to the simulation of realistic hole failure. The results further reveal the differences of sand production between the two sandstones, and can provide some theory support for the sand production in oil and gas field.

Study on failure mechanical characteristics and damage constitutive model of sandstone with different numbers of holes

Abstract The existence of holes in rock is one of the key factors for the instability of underground rock mass engineering. Combined with acoustic emission equipment, uniaxial compression tests of rock specimens with different numbers of holes in the rock were carried out. The results show that with the number of holes increases, the value of peak strength and elastic modulus of the rock decrease. The acoustic emission (AE) counts gone through stable, slow increase, a sudden increase and towards zero four stages and there are corresponding to the initial compaction stage, elastic stages, strain hardening stage and post-peak strain softening stage of the stress-strain curves approximately. Based on the AE events, damage variables of rocks were obtained. The damage evolution process of rock can also be divided into three parts, including stable damage stage, slowly increasing damage stage and sharply increasing damage stage. According to Duncan model, the damage variable is introduced to obtain the rock damage constitutive model. No matter it is the pre-peak initial compaction stage, the linear elasticity stage, the strain hardening stage or the post-peak strain softening stage, the fitting curves are in good agreement with the test curves. It also illustrates the rationality of the damage constitutive model.

Modelling Unsaturated Soil Response Beyond Residual Suction State via Vapor-Pressure Controlled Triaxial Testing

Most of the previous research has been focused on developing and validating constitutive models to predict response of unsaturated soils in low-medium suction range. However, there is a scarcity of efforts in developing soil models to simulate its mechanical response in high suction range, particularly above the residual suction. This article presents a new constitutive model introducing net stress and suction as two independent variables. Furthermore, non-associative flow rule incorporating modified stress-dilatancy relationship to take unsaturated state into account is introduced to improve the model results in low-medium to high suction range. The essential soil model parameters are calibrated using suction-controlled triaxial test results for predictions of compacted silty sand response at high values of total suction above residual suction. Preliminary simulations show that proposed model can reasonably simulate the post-peak strain softening response obtained from suction-controlled CTC tests above residual suction value with reasonable accuracy. Although, the proposed model captures initial compression followed by dilation volumetric response with reasonable accuracy, it needs some improvements to be able to capture volumetric response accurately over entire suction range.

Strength of Laboratory Synthesized Hydrate‐Bearing Sands and Their Relationship to Natural Hydrate‐Bearing Sediments

AbstractThe strength of hydrate‐bearing sediments is an important input parameter for numerical simulations for evaluating the long‐term future gas production from these sediments and the risks associated with such activities on the environment. Studies on laboratory synthesized, and natural, hydrate‐bearing coarse‐grained soils exhibit similar behavior, where increasing hydrate saturation increases specimen strength and stiffness with the corresponding development of peak stress, postpeak strain softening and tendency for sample dilation, which is suppressed with increasing effective stress, although strength is increased. For synthesized specimens, hydrate growth at grain contacts leads to “cementing” behavior and the largest increase in strength, which is subdued when hydrate growth is prevented at these locations. Sample disturbance in natural samples lead to lower strength and stiffness compared to laboratory synthesized samples. Unconfined compression shear tests on natural samples highlight the strong “cementing” effect of gas hydrates on coarse‐grained soils. The strength of natural sediments appears strongly correlated with particle size and clay content, with smaller particle and increasing clay content reducing strength for a given hydrate saturation. The strength parameters, friction angle, and cohesion appear to depend on sample type. For synthesized specimens, friction angle was reasonably independent of hydrate saturation while cohesion increased in an exponential manner, with the largest increase occurring when hydrate growth is at particle contacts. In contrast, friction angle appeared to increase with a corresponding reduction in cohesion for natural hydrate‐bearing sediments. However, these observations may be related to sample disturbance and stress conditions under which the data were acquired.