Post-peak Strength Research Articles

Grain-size composition effect on flexural response and pore structure of cementitious tail-rock fills with fiber reinforcement

This paper explores the grain-size composition effect on flexural and micro-structural features of fiber reinforced cementitious tail-rock fill (FRCTRF). The FRCTRF mixes considered contained a stationary solid concentration of 70 wt% and a cement/tail rate of 1:6, and were cured for an age of 7-day for strength tests and microstructure. Three-point bending test shows that FRCTRF’s bending property is upgraded by totaling gravel rock. Adding fiber to FRCTRF’s bottom can enhance its peak deflection. With rising gravel particle size/dosage, FRCTRF’s peak deflection displays a trend of falling first and then growing. Accumulating polypropylene fiber could advance FRCTRF’s post-peak strength features as well. FRCTRF sample containing gravel has a large stress drop, and adding gravel rock could essentially boost FRCTRF’s post-peak brittle-ability. In conclusion, this study provides a strong scientific and theoretical underpinning for optimizing artificial false roofs employed recently in modern underground metalliferous mining operations.

Investigation on Strength and Flexural Behavior of PVA Fiber-Reinforced and Cemented Clayey Soil

Adding cement to soft soils may lead to brittle behavior and the occurrence of sudden damage. Methods to further improve the tensile and flexural properties of cemented clay are noteworthy topics. This paper mainly focuses on the effect of cement and moisture content on the strength and flexural properties of cemented clay reinforced by PVA fiber. The selected clayey soil was a kaolin with cement content of 5%, 10%, and 15% and moisture content of 50%, 56%, 63%, and 70%. The results show that the incorporation of 0.6% fiber can effectively improve the deformability of cemented clay in unconfined compression tests (UCS). The strengthening effect of fiber, as seen in the peak strength and post-peak strength of UCS, was significantly related to cement content. As the water content increased, the compressive strength of the fiber-reinforced cemented clay decreased, but its load-bearing capacity enhanced. When the cement content was 15%, the splitting tensile strength of fiber-reinforced cemented specimens increased by 11% compared to cemented soil, but the deformability of the specimens became poor. In the cement-content interval from 5% to 10%, the bending toughness was significantly improved. Sufficient cement addition ensures the enhancement of PVA fibers on strength and flexural properties of cement-stabilized clayey soil.

Mechanical Behaviour of Soil Treated with Chitosan and Calcium Metasilicate Considering the Fungal Growth

Biopolymers have been widely experimented with as organic stabilizers in the last decade for improving soil properties. However, the high nutritional value of some biopolymers like chitin, carrageenan, casein, and chitosan can also promote microbial growth which can affect the improvement in the strength of biopolymer-stabilized soil. This study investigates the mechanical behaviour of clay treated with chitosan at dosages of 0.5, 1.0, 1.5, and 2.0% at various curing periods of 7 d, 28 d, 56 d, and 90 d and also observes the fungal growth, the conditions favourable to fungal growth, and the effect of an inorganic secondary additive on the mechanical behaviour of treated soil. The study shows that fungal growth is higher with the time and dosage of chitosan. The strength of chitosan-treated samples increased with both dosage and age despite the fungal growth observed on the treated soil, as did the fungal growth. On treating the soil with 2% chitosan, the percentage increase in strength was nearly 14.39%, and on the 56th day, it was phenomenally increased to 1534.39%. In an attempt to control the fungal growth, a secondary additive, calcium metasilicate (calsil), was added to various dosages of chitosan-treated soil (CTS). The secondary additive did not completely stop the fungal growth but certainly controlled fungal growth. Chitosan and calsil are hydrophilic, increasing OMC by 67% and 150% for the high CTS and calsil–chitosan-treated soil (CCTS) doses. Calsil coated the soil particles and prevented closer packing under compaction, reducing MDUW by 7.8% and 18% for CTS and CCTS at maximal dosage. The development of hydrated cementitious products made the soil brittle, causing the post-peak strength of CCTS samples to diminish significantly with age. FTIR spectroscopy showed hydrogen bonding strengthening CTS, while XRD revealed cementitious compounds in CCTS. The strength of the soil treated with chitosan and calsil showed a higher strength than soil treated with only chitosan.

Elaborating the 3D microstructural characteristics and strength softening mechanical mechanism of fiber-reinforced recycled aggregate concrete

Recycled aggregate concrete (RAC) is a sustainable and low-carbon construction material, but it tends to have inferior physico-mechanical properties compared to natural aggregate concrete. This study aims to enhance these properties to make RAC a viable alternative for broader construction applications. By incorporating steel fibers (SF) and polypropylene fibers (PPF) into RAC, the mechanical properties, particularly crack resistance and post-peak strength softening, were significantly improved. Extensive low-cycle loading tests were conducted to assess the strength softening behavior and energy dissipation capacity. The results showed that fibers increased post-peak strength softening resistance by up to 30 % for SF and 25 % for PPF. Proposed strength softening models based on residual strain accurately predict the effects of fiber dosage on the composite’s properties, providing a technical foundation for RAC engineering applications.

Strength Reduction Method for the Assessment of Existing Large Reinforced Concrete Structures

This work presents a new developed assessment methodology based on strength reduction and finite element methods which is suitable for existing large reinforced concrete structures commonly used in hydraulic constructions. The methodology is based on a reloading phase of the finite element model and is preceded by an intermediate reduction phase of concrete tensile strength and an initial loading phase up to service level. Rosenblueth’s point estimate method was used to compute a global resistance factor and to deduce a design resistance value of the structure. After validations, the methodology was applied to two existing complex and large hydraulic structures: a spiral case and a draft tube. If compared with existing methodologies using sophisticated non-linear finite element methods, the developed approach is simpler, more practical, and provides results that are on the conservative side. Considering the difficulties in characterizing the tensile peak and post-peak strength of concrete, along with uncertainties regarding the damage conditions of facilities, the developed methodology is deemed robust and well suited for assessing existing critical large reinforced concrete infrastructures.

Investigation of constitutive properties of high plasticity clay soils mixed with crushed rubber tire waste

Addressing the enormous waste resulting from discarded worn rubber tires is an environmental challenge. Recycling and using crushed rubber tire waste (CRTW) in construction materials can help in addressing this challenge. This study investigates the effect of addition of CRTW on the engineering properties of high plasticity clay soils (HPCS). There is a paucity of research in the application of CRTW in HPCS. This research tries to fill this research gap. Specifically, this study seeks to investigate the effect of mixing CRTW on the constitutive properties of HPCS. After identifying a locally available HPCS, mixtures of the clay and several percentages (0%, 6%, 12%, 18%, and 24%) by weight of CRTW were prepared. A range of CRTW shapes and sizes were investigated. Three different particle shapes of CRTW (granular rubber, rubber chips, and rubber fiber), and two particle sizes (fine and coarse) were studied. The parameters studied included unconfined compressive strength (UCS), strain at failure, post-peak strength loss (PPSL), modulus of elasticity, failure modes/mechanisms, repeatability of tests results, and examination of CRTW particles and mixtures via binocular and SEM microscope. Our findings unveiled that the highest level of repeatability was observed in granular CRTW, with a maximum variability of only 5%. Moreover, the mixtures containing granular CRTW exhibited, on average, 10% and 15% higher strength and modulus of elasticity, respectively, in comparison to mixtures incorporating other shapes of CRTW. In general, the HPCS-CRTW mixtures displayed higher shear strains, averaging 25% greater than pure HPCS. Furthermore, the addition of CRTW to HPCS resulted in a reduction of its PPSL and a transition in behavior from brittle to slightly ductile. Examination of failed specimens revealed the existence of two primary failure modes: shear plane failure and shear plane failure accompanied by multiple vertical cracks within the mixtures. These results suggest that the utilization of granular CRTW in HPCS can improve certain properties of HPCS. However, it is advisable to limit the rubber content in this mixture to 6% to mitigate significant adverse effects on its strength.

Damage constitutive model of polypropylene-fibre-reinforced recycled aggregate concrete

Adding polypropylene fibre (PPF) to recycled aggregate concrete (RAC) not only improves performance but also has economic benefits. The effects of single-blend and double-blend micro- and macro-PPFs in RAC specimens were studied. Micro- and macro-PPFs were used to design and produce 30 groups of PPF-reinforced RAC specimens with 0%, 25% and 50% coarse aggregate (CA) substitution rates. Controlling the fibre mixing proportions, the stress–strain curve, elastic modulus, peak strength, peak strain and acoustic emission amplitude–frequency extremum (AFE) of each group of specimens were obtained. The elastic modulus and peak stress of specimens without PPFs decreases gradually with an increase of the CA substitution rate. However, there was a certain increase in elastic modulus and peak stress when PPFs were added. A damage constitutive model for PPF-reinforced RAC was established. By fitting this model, it was found that although the elastic modulus and peak stress of the RAC specimens increased by a certain extent, the fitting parameters of RAC were greater than those of ordinary concrete and the RAC post-peak strength was lower. The evolution law of acoustic emission AFE of PPF-reinforced RAC was studied. It was found that the cumulative AFE of RAC with PPF was larger, indicating that the PPFs limited crack propagation and increased the fracture energy.

Insights from an extensive triaxial testing campaign on a shale for comparative site characterization of a deep geological repository

Several boreholes were drilled for site comparison of a deep geological repository (DGR) in Northern Switzerland. The main target of the exploration program was the >100m thick Opalinus Clay, the designated host rock encountered at approximately 450 to 1000 m depth in three different sites. This contribution focuses on the evaluation of geomechanical properties and the deformation behavior from the triaxial testing campaign, both aspects relevant to construction and the assessment of the long-term safety of a DGR. Some 140 triaxial tests were performed on cores from seven different boreholes to evaluate potential differences in material properties by depth and geographic location. Core sampling, preparation chain, and testing protocols were validated before the campaign, and three laboratories were commissioned to perform the tests. A comparison of basic properties from cores used for triaxial testing with a much larger database of complementary core analyses and geophysical logging demonstrates that the performed tests cover the range of expected material properties. Limited to no differences in strength and stiffness are detected from cores at different depths and sites. Despite a relatively large variation in bulk mineralogy of the formation (e.g. clay-mineral content varying between 35 and 75 wt%), the strength values of Opalinus Clay vary only moderately, with equivalent (calculated) unconfined compressive strengths of 21 ± 5 MPa, for loading directions parallel or perpendicular to bedding. This contrasts with the results of Opalinus Clay from the Rock Laboratory at Mont Terri, where the effect of material composition was more relevant. Assuming a Mohr-Coulomb-type failure law, the transition from peak to post-peak strength comes at the expense of cohesion, and only a small reduction of the shear strength angle. Hence the burial history, tectonic overprint, and current depth mainly control the intact properties by additional cohesion, whereas the post-peak behavior is mainly controlled by bulk mineralogy.

Impact of directly accounting for post-peak strength loss on the dynamic response of a soil column during earthquake loading

Impact of directly accounting for post-peak strength loss on the dynamic response of a soil column during earthquake loading

A multi-strut model for the hysteresis behavior and strength assessment of masonry-infilled steel frames with openings under in-plane lateral loading

The analysis of masonry-infilled frames (MIFs) with openings is a complex problem in structural engineering. Previous studies have shown that when an infill panel has an opening, it behaves as four separate subpanels around the opening. Therefore, it can be conceived that a perforated masonry infill panel behaves as four inclined compression-only equivalent struts in each direction. This paper presents a multi-strut model (MSM) using the equivalent strut concept for the nonlinear analysis of masonry-infilled steel frames (MISFs) with openings. The MSM consists of two inelastic side pier struts connected to the surrounding frame joints using rigid trusses representing the subpanels above and below the opening. The model incorporates an envelope curve and a hysteretic law to define the initial stiffness, peak strength, and post-peak strength behavior of the inclined struts under reversal loads. The MSM was used to analyze the lateral load behavior of tested MISFs with openings found in the literature. It was shown that the proposed model is efficient and can predict the stiffness and capacity of MISFs with openings under both monotonic and cyclic lateral loadings.

Experimental study on the effect of temperature on HDPE geomembrane/geotextile interface shear characteristics

Geomembranes (GMBs) and geotextiles (GTXs) are the most widely used geosynthetics in landfills and other barrier systems. While various temperature environments may be encountered in practice, the interface shear characteristics of geosynthetics under different temperatures are still not clear. Shear tests of the interface between a high-density polyethylene GMB and nonwoven GTX are performed using a temperature-controlled submerged direct shear apparatus. The testing temperatures range from 10 °C to 70 °C, which covers most of the situations commonly encountered in engineering. The shear behaviors of the textured GMB/GTX interface and smooth GMB/GTX interface are presented, and the mechanism of the temperature influence is analyzed according to the test results and phenomena. Temperature has a significant impact on the GMB/GTX interface peak strength and post-peak strength, and maximum interface shear strength could be obtained when the temperature is approximately 30–40 °C. The influencing mechanisms of temperature on the GMB/GTX interface shear strength are thoroughly discussed. The shear characteristics of the GMB/GTX interface under different temperatures are critical to the stability analysis of geosynthetic slopes in special condition, and this study can also provide a reference for the effect of temperature on the shear behavior of other geosynthetics.

New accelerated rock creep model considering nonstationary viscosity coefficient

Accelerated creep models are popular research topics in rock mechanics. By analyzing the variation in the viscosity coefficient in the accelerated creep stage and defining the viscoplastic internal variable, a general evolution law for the viscosity coefficient was revealed, and a widely applicable accelerated creep model was proposed. First, the creep test data of 24 rock types were collected and analyzed. Subsequently, the contrast between the strength decrease in the accelerated creep-subsequent failure stage and the post-peak strength decrease in the elastoplastic process was evaluated, and the viscoplastic internal variable in the accelerated creep stage was defined. Subsequently, the evolution function between the normalized viscosity coefficient and the viscoplastic internal variable was established. Based on the test data for different rocks, the predicted curves accurately captured the evolution of the normalized viscosity coefficient with the viscoplastic strain increment and confining pressure in the accelerated creep stage. A new accelerated creep model was constructed by modifying the linear viscoplastic part of the Nishihara model using an established evolution model of the viscosity coefficient. The model demonstrated agreement with the experimental data for different rocks and yielded results close to the monitored tunnel convergence data.

Influence of Lateral Pressure on the Mechanical Performance of Bolted Specimens under Biaxial Compression

The influence of lateral pressure (σ2) on the stability of the surrounding rock of roadway increases after excavation. The rock bolt is usually used to improve the stability of the surrounding rock. Therefore, it is important to understand the biaxial compressive behaviors of the bolted samples influenced by lateral pressure. In this study, biaxial compression experiments are carried out to investigate the biaxial compressive properties of bolted rock samples influenced by lateral pressure. The results show that bolting can improve the peak strength, inhibit the post-peak strength attenuation and reduce the pre-peak brittleness of the bolted rock mass. With the increase of lateral pressure, the strength and elastic modulus of the bolted samples increases approximately parabolic and linearly, respectively. The failure modes of the bolted samples influenced by lateral pressure can be divided into splitting failure and compression-shear failure. A reinforcement mechanism of bolt is observed, namely axial action, axial and transverse action at the pre- and post-peak stages of the bolted samples. Based on a modified true triaxial Mohr-Coulomb strength criterion and this bolt reinforcement mechanism, a new method for calculating the equivalent cohesion and equivalent internal friction angle of the bolted specimens under biaxial compression is proposed. The research results of this paper have certain reference value for the stability control of roadway

Back-analyses of soft soil failure with "strain-softening" behavior by the "equivalent sensitivity" concept

Stability analyses of slopes in soft soils are usually affected by strain-softening, resulting in unrealistic (unconservative) safety factors. The loss of post peak strength cannot be accounted for by classic limit equilibrium analyses. In practice, however, the overall loss of soil strength is generally approximated by Bjerrum correction factor μ ≤ 1, which is believed to account for the different failure velocities during the field tests (usually vane tests) and the actual failure in the field, in addition to anisotropy (Schnaid & Odebrecht, 2012). The objective of this work is to demonstrate that strain-softening reduces the overall safety factor to a value nearly equivalent to the application of Bjerrum’s correction factor. To accomplish this, a simple constitutive model (Mohr-Coulomb with residual stress) is used for total stress finite element analyses by means of the concept of “equivalent sensitivity” proposed by Pereira Pinto (2017). The results showed that equivalent sensitivity can be a great instrument to simulate the strain-softening behavior of soft soils.

Damage characterization and microscopic mechanism of steel slag-cemented paste backfill under uniaxial compression

The utilization of steel slag-cemented iron tailings for preparing mine backfill materials can effectively consume industrial solid waste generated from steel production and significantly reduce backfilling costs. The study analyzed the influence and mechanisms of steel slag (SS) content on the mechanical damage characterization of steel slag-cemented paste backfill (SS-CPB) through uniaxial compressive strength (UCS) tests and microscopic testing methods such as X-ray diffraction (XRD) and a scanning electron microscope (SEM). The engineering applicability and economic feasibility of the material were evaluated. The main conclusions were as follows: (1) With the increase of SS content, the strength of SS-CPB first increases and then decreases, with the highest strength observed at a 10% SS content. (2) The inclusion of SS in SS-CPB leads to higher peak strain and post-peak strength, demonstrating significant plastic deformation characteristics. (3) When the SS content increases from 30% to 60%, the Ca(OH)2 content in SS-CPB hydration products decreases by 20.2%, and internal micropores increase. (4) When the SS content reaches 30%, the damage mode of SS-CPB changes from purely splitting failure to a plastic combination of splitting and shear failure. These research findings provide a new application model for the collaborative utilization of steel slag, tailings, and other solid wastes.

Thermo-mechanical behaviour of microbial induced carbonate precipita-tion (MICP) sand for geothermal pavements

Introduction
 Ground source heat pump (GSHP) or shallow geothermal energy systems are gaining attention for helping combat global warming and the negative effects of urbanisation caused by human activities. In recent decades, energy geo-structure techniques have developed by using subsurface infrastructures to exchange heat with the ground. These techniques can provide space heating and cooling while still preserving the primary structural function. As a result, they have become a valuable part of geothermal energy systems. Researchers have developed an understanding of incorporating ground heat exchangers into foundation piles, retaining walls, and tunnel linings with modest additional cost [1-4]. Pavements are also structures in contact with the ground that have the potential to be used as energy geo-structures (i.e., geothermal pavements), yet, their use has not been extensively studied [5-8].
 Soil thermal conductivity is an important factor influencing the efficiency of geothermal pavements since heat transfer in soils occurs primarily by conduction [9]. Microbially induced calcium carbonate (CaCO3) precipitation (MICP) is an innovative technique for strengthening sandy soils by coating and binding soil grains with calcium carbonate crystals. The distribution and arrangement of the CaCO3 within the pore spaces play a crucial role in determining the resulting strength of the treated sand. In addition, these crystals can act as thermal bridges to enhance the soil's thermal conductivity [10]. Combining geothermal pavements with MICP sand is still nascent, and the limited number of studies that exist mainly focus on the associated thermal property changes [11]. However, since the principal function of pavements is transmitting (dynamic) loads to the subbase and the underlying soil, the thermal conductivity of the MICP-treated pavement may vary as a result of the applied mechanical loads (e.g., due to the partial or total loss of thermal bridges and/or particle rearrangement). This research thus investigates the changes in the thermal conductivity of MICP-treated sands as they are subjected to quasi-static triaxial compression. The experimental results collected can deepen our understanding of the thermo-mechanical behaviour of MICP-treated sands and provide practical insights for using MICP to reinforce the subbase or underlying soil of geothermal pavements.
 Methodology
 This research performed a series of quasi-static triaxial tests on MICP-treated Houston sand, fine-grained, high-purity silica sand. Sporosarcina pasteurii (strain designation DSM 33) was used for the MICP treatment of the soil specimen. To study the effect of CaCO3 content on the thermo-mechanical performance of MICP-treated sand, three cementation solution treatment cycles were applied, yielding theoretical CaCO3 contents of 0.6%, 1.6% and 2.7% by weight, respectively. Details on the MICP treatment of the samples can be found in [12]. Samples for triaxial testing were treated in cylindrical tubes of 50mm inner diameter and 100mm height. To investigate the influence of the CaCO3 content on the soil thermal conductivity, MICP-treated specimens were air-dried prior to triaxial testing Triaxial tests were subsequently conducted in dry conditions to isolate the effect of the MICP and avoid the influence of water content on soil thermal conductivity (λ). Furthermore, a new miniaturised transient sensor was embedded in the triaxial samples to monitor the λ changes during the sharing phase [12].
 Results
 An example of the evolution of the deviatoric stress with axial strain under 50kPa confining stress (σ3) in the triaxial cell is shown in Figure 1a. Compared to the untreated sand, MICP-treated samples lead to higher peak strength and stiffness. Importantly, λ changes during triaxial testing for different CaCO3 contents are summarised in Figure 1b. Results indicate that the increase in CaCO3 content can significantly improve λ, and that λ rapidly decreases post-peak strength due to dilation and CaCO3 bond breakage. Once the samples reach its ultimate state, λ remains unchanged.

Numerical modelling of post-failure behaviors of coal specimens

A modelling approach consisting of best-fit relations to estimate the post-yield strength parameters is presented for simulating post-peak behavior beyond the point of residual strength of coal pillars having different w/h ratios. The model was developed based on back-analysis of the complete stress-strain behavior of specimens belonging to six different Indian coal seams with different w/h ratios of 0.5–13.5. It was found that the simultaneous degradation of the cohesion and friction angle of the Mohr-Coulomb rock material characterizes the post-peak strength behavior of the rock. The resulting expressions are simplistic as they require parameters that can be easily determined using uniaxial and triaxial compression results. Eventually, the developed model was validated by simulating the triaxial tests of coal specimens with different sizes under varying confining stresses and comparing its findings with the published test results. The study showed that its implementation in the numerical model could reproduce laboratory-observed mechanical response, deformation behavior, and failure mechanism very closely.

GMX/GDC strength loss mechanisms

This paper provides insight into the causes of post-peak strength loss for textured geomembrane (GMX) and nonwoven geotextile (NGT) interfaces. The NGT can be part of a geosynthetic drainage composite (GDC) or a stand-alone NGT. The study used ring shear tests where one of the two interface materials was replaced after reaching a residual strength condition and the test was restarted to measure the change in interface strength. The interface strength loss from peak to large displacement (LD) strength primarily comes from three mechanisms: (1) geomembrane wear, (2) breakage and combing of fibers in the NGT, and (3) reduction of the hook and loop effect between GMX asperities and fibers of the NGT. The source of interface strength loss from LD strength to the residual value mainly comes from breakage and continuous combing of NGT fibers parallel to the direction of shear in ring shear tests. Scanning electron microscopy photographs of the GMX and NGT before and after shearing confirm wear and smoothing of GMX asperities and the combing of NGT fibers in the direction of shear.

Mechanical behavior of sandstone during post-peak cyclic loading and unloading under hydromechanical coupling

This paper investigates mechanical behaviours of sandstone during post-peak cyclic loading and unloading subjected to hydromechanical coupling effect, confirming the peak and residual strengths reduction laws of sandstone with water pressure, and revealing the influence of water pressure on the upper limit stress and deformation characteristics of sandstone during post-peak cyclic loading and unloading. Regarding the rock strength, the experimental study confirms that the peak strength σp and residual strength σr decrease as water pressure P increases. Especially, the normalized strength parameters σp/σpk and σr/σre was negatively and linearly correlated with the P/σ3. Moreover, the Hoek-Brown strength criterion can be applied to describe the relationship between effective peak strength and effective confining stress. During post-peak cyclic loading and unloading, both the upper limit stress σp(i) and crack damage threshold stress σcd(i) of each cycle tend to decrease with the increasing cycle number. A hysteresis loop exists among the loading and unloading stress–strain curves, indicating the unloading deformation modulus Eunload is larger than the loading deformation modulus Eload. Based on experimental results, a post-peak strength prediction model related to water pressure and plastic shear strain is established.

Prediction of post-peak stress-strain behavior for sensitive clays

Unlike typical soils, sensitive clays undergo extensive post-peak strength degradation with increasing strain and finally disintegrate into a remolded liquid state. Realization of post-peak stress-strain behavior of sensitive clay up to large strains is vital in assessing large deformation problems such as landslides and mud flows. The conventional experimental approaches are uncertain about accurately determining the post-peak stress curve up to large strains (>100%) owing to rapidly increasing testing problems at increasing strains. This necessitates the exploration of an alternative scientific approach to predict the complete stress-strain curve for sensitive clays, which is addressed in this paper. Post-peak stress-strain curves of sensitive clays for different sites are obtained by converting remolding index vs. strain energy curves. Using site-specific data from eastern Canada sites, a mathematical expression is proposed to predict the complete stress-strain curve. Subsequently, an equation is developed for predicting remolding energy based on the stress-strain curve. Finally, it is observed that the post-peak stress-strain behavior is highly site-specific and can be mathematically expressed with a combination of exponential and linear strain-softening curves. Overall, the knowledge of the complete stress-strain behavior contributes greatly to the prediction of post-failure movements closer to reality.