Uniaxial Compression Tests Research Articles

Smart Crowding on pH-Induced Elasticity of Weakly Anionic poly(N-Isopropylacrylamide)-Based Semi-Interpenetrating Polymer Networks via Integration of Methacrylic Acid and Linear Polyacrylamide Chains.

Weakly anionic semi-interpenetrating polymer networks (semi-IPNs), comprised of copolymer poly(N-isopropylacrylamide-co-methacrylic acid) P(NIPA-MA) and linear poly(acrylamide) (LPA) chains as macromolecular crowding agent, are designed to evaluate pH-induced swelling and elasticity. Uniaxial compression testing after swelling in various pH-conditions is used to analyze the compressive elasticity as a function of swelling pH and LPA-content. The swelling of P(NIPA-MA)/LPA semi-IPNs is strongly pH-dependent due to MA units incorporated into the copolymer network which already exhibits temperature-sensitivity by presence of PNIPA counterpart. Since the behavior of semi-IPNs is a combination of PMA, LPA, and PNIPA moieties, the sensitivity of swelling to external pH can be modified with increasing swelling temperature. At high pH conditions, LPA-doped semi-IPNs show elasticity representing soft and loosely cross-linked structure. Elastic modulus is higher in acidic pH condition due to the less swelling tendency, while in basic pH, the modulus decreases significantly in coordination with swelling. Oscillatory swelling reveals how fast semi-IPNs can respond to environmental pH change (2.1-10.7). By describing adsorption potential of semi-IPNs for cationic methylene blue uptake by pseudo-first-order and Freundlich model, the designed poly(NIPA-MA)/LPA semi-IPNs emerge as promising smart materials in applications requiring rapid response to changes in temperature and pH via diffusional properties.

Microstructural Evolution and Damage Mechanism of Water-Immersed Coal Based on Physicochemical Effects of Inorganic Minerals

Coal seam water injection technology enables seam permeability enhancement and facilitates outburst risk reduction. This study investigated the microscale effects of water infiltration on coal and the evolution mechanisms of its mechanical properties. To this end, we systematically analyzed dynamic changes (such as mineral composition, pore structure, and mechanical performance) in coal soaked for various durations using X-ray diffraction, low-field nuclear magnetic resonance (NMR), and uniaxial compression testing. The results indicate: (1) the coal NMR T2 spectrum displays three characteristic peaks, corresponding to rapid water absorption, uniform transition, and stabilization stages of soaking traditionally divided according to peak area variation trends. (2) The coal strength decreases with progressive soaking, influenced by water content, pore volume, mineral composition, etc. Its compressive strength and elastic modulus drop by 22.4% and 19.5%, respectively, compared to the initial values. (3) The expansion of clay minerals during immersion reduces average pore size. In contrast, quartz particle displacement, pore water movement, and soluble mineral dissolution increase pore volume, reducing the overall structure strength. (4) The dominant factors driving the degradation of mechanical properties vary across immersion stages, including water content and specific mineral concentration. This work offers new insights into how hydraulic technology alters coal seams, providing theoretical support for optimizing water injection strategies in the seam.

Marine Geo-Polymer Cement Treated with Seawater, Alkaline Activators, Recycled Particles from Paste, and Recycled Particles from Glass

This study aims to develop the marine geo-polymer cement that was produced with seawater, recycled particles from paste, recycled particles from glass, and alkaline activators, including NaOH or Na2O·3.3SiO2. The physicochemical properties and strength of MGPC were investigated with a Uniaxial Compression Test, Particle Size Analysis, Energy Dispersive Spectrometer, X-ray Diffraction, and Thermal-field Emission Scanning Electron Microscopy. The results indicated that the main hydration products in MGPC were calcium carbonate (CaCO3), silica (SiO2), sodium aluminosilicate hydrate (Na2O·Al2O3·xSiO2·2H2O, N-A-S-H), and aluminum calcium silicate hydrate (CaO·Al2O3·2SiO2·4H2O, C-A-S-H). The calcium carboaluminate (3CaO·Al2O3·CaCO3·32H2O, CO3-AFm) in MGPC was converted into CaCO3 and Friedel’s salt (3CaO·Al2O3·CaCl2·10H2O), which prompted the carbon sequestration. The microstructure of MGPC prepared using Na2O·3.3SiO2 was based on RPG as the matrix, with N-A-S-H, C-A-S-H, and fibrous AFt growing on the periphery. This structure reduces the impact of the alkali–silica reaction on the material and improves its compressive strength. Therefore, the MGPC developed in this study shows the exact benefits of freshwater and natural minerals saving, carbon sequestration, and damage resistance.

Geometric and Mechanical Properties of Ti6Al4V Skeletal Gyroid Structures Produced by Laser Powder Bed Fusion for Biomedical Implants

Skeletal gyroid structures possess promising applications in biomedical implants, owing to their smooth and continuously curved surfaces, open porosity, and customisable mechanical properties. This study simulated the geometric properties of Ti6Al4V skeletal gyroid structures, with relative densities ranging from 1.83% to 98.17%. The deformation behaviour of these structures was investigated through a combination of uniaxial compression tests and simulations, within a relative density range of 13.33% to 50% (simulation) and 15.19% to 41.69% (experimental tests). The results established explicit analytical correlations of pore size and strut diameter with the definition parameters of the structures, enabling precise control of these dimensions. Moreover, normalised Young’s modulus (ranging from 1.05% to 20.77% in simulations and 1.65% to 15.53% in tests) and normalised yield stress (ranging from 1.75% to 17.39% in simulations and 2.09% to 13.95% in tests) were found to be power correlated with relative density. These correlations facilitate the design of gyroid structures with low stiffness to mitigate the stress-shielding effect. The presence of macroscopic 45° fractures in the gyroid structures confirmed that the primary failure mechanism is induced by shear loads. The observed progressive failure and plateau region proved the bending-dominant behaviour and highlighted their excellent deformability. Additionally, the anisotropy of gyroid structures was confirmed through variations in stress and strain concentrations, deformation behaviour, and Young’s modulus under different loading directions.

Comparison of Different Additives and Ages on Mechanical and Acoustic Behavior of Coal Gangue Cemented Composite

Cemented backfill represents a significant trend in mine filling methods; however, it often exhibits high brittleness and limited resistance to failure, which can restrict its practical application. This study investigates the mechanical properties and damage evolution of fiber-reinforced coal gangue cemented materials (CGCMs) at various curing times using uniaxial compressive tests, acoustic emission (AE) analysis, and scanning electron microscopy (SEM). Specimens were created with different fillers, including carbon fibers (CFs), steel fibers (SFs), and carbon black (CB), and subjected to uniaxial compression until failure. Control specimens without fillers were also tested for comparison. The microstructure of the specimens was examined using scanning electron microscopy (SEM). The findings indicate that (1) the compressive strength of filler-reinforced CGCMs increases between 7 and 14 days of curing but decreases thereafter, with CB significantly improving early-age strength; (2) specimens reinforced with CFs and SFs exhibit significantly enhanced toughness in their post-cracking response; (3) AE events during specific stages can effectively identify the reinforcing effects of CFs and SFs; (4) the presence of fillers improves resistance to shear cracks, with CFs and SFs being more effective than CB; and (5) adding CB results in a denser and more stable hydration product structure, while CFs and SFs lead to a more porous structure with increased cracking.

Gelation and Cryogelation of Chitosan: Origin of Low Efficiency of Diglycidyl Ethers as Cross-Linkers in Acetic Acid Solutions

Although diglycidyl ethers of glycols (DEs)—FDA-approved reagents for biomedical applications—were considered unsuitable for the fabrication of chitosan (CH) hydrogels and cryogels, we have recently shown that CH cross-linking with DEs is possible, but its efficiency depends on the nature of the acid used to dissolve chitosan and pH. To elucidate the origin of the low efficiency of chitosan interactions with DEs in acetic acid solutions, we have put forward two hypotheses: (i) DEs are consumed in a side reaction with acetic acid; (ii) DE chain length strongly affects the probability of cross-linking. We then verified them using FT-IR spectroscopy, rheological measurements, and uniaxial compression tests. The formation of esters in acetic acid solutions was confirmed for ethylene glycol diglycidyl ether (EGDE) and poly(ethylene glycol) diglycidyl ether (PEGDE). By the 7th day of gelation at pH 5.5, the G’HCl/G’HAc ratio was 5.1 and 1.5 for EGDE and PEGDE, respectively, indicating that the loss of cross-linking efficiency in acetic acid solution was less pronounced for the long-chain cross-linker. Under conditions of cryotropic gelation, only weak cryogels were obtained from acetic acid solutions at a DE:CH molar ratio of 1:1, while stable cryogels were fabricated at a molar ratio of 1:20 from HCl solutions.

Durability of Two-Component Grout in Tunneling Applications: A Laboratory Test Campaign

Today, two-component grout is the most widely used backfilling technology in shielded mechanized tunneling. Despite its intensive use, however, very scant information pertaining to the durability of this material is available in the scientific literature. In this work, the aging of two-component grout is studied by curing grout samples using three different modalities. Furthermore, the action of air on two-component grout is studied by assessing the dehydration process, which is a phenomenon that occurs when the material is cured without being completely embedded in soil/rock. Uniaxial compression tests and three-point flexural tests have been carried out for mechanical characterization. The results reveal that in a curing environment made of sand, a moisture of 5% is sufficient to guarantee correct curing of the grout and extend the mechanical performance to three years, whereas the action of air is potentially dangerous, since the grout suffers strongly from dehydration. Despite this dehydration process, however, the mechanical performance of the grout also tends to increase for samples cured under the action of air until a very high level of cracking and shrinkage is reached. A discussion of the limitations on the uniaxial compression strength as the main mechanical parameter for the characterization of two-component grout concludes the work.

Effect of moisture on mechanical and physical properties of coals: a uniaxial compression study

The estimation of mechanical and physical properties of coal reservoirs is important for the successful exploration and development of coalbed methane (CBM). Unlike conventional sandstone reservoirs, coal reservoirs exhibit greater sensitivity to stress, resulting in distinct mechanical and physical behaviors. In this study, uniaxial compression tests were performed on both low-rank and high-rank coal samples under different moisture conditions to reveal the mechanical and physical property changes with stress. The results indicate that during axial stress loading (up to 2.8 MPa), axial strain initially increases rapidly and subsequently at a slower rate, with an axial strain of 0.13–0.25% observed at the maximum axial stress. The instantaneous Young’s modulus increases linearly before stabilizing, ranging from 618.01 to 4861.10 MPa, while the Poisson’s ratio remains relatively constant or increases linearly, ranging from 0.002 to 0.165. This results in a negative exponential decrease in both porosity and permeability, with maximum reductions of 1.77–4.21% and 5.38–12.25%, respectively. The mechanical properties of coal are influenced by both the cementation effect of water at low water saturation and the softening effect at high water saturation, which results in axial strain decreases and then increases as the water saturation increases. Concurrently, the elastic modulus initially increases and then decreases, while the Poisson’s ratio exhibits a less pronounced change or tends to increase. Consequently, there is a trend in which porosity and permeability first increase and then decrease. In addition, during stress unloading, the influence of water in coal induces a notable strain hysteresis phenomenon in water-containing coal samples, and this phenomenon is more obvious in the low-rank coals.

Tests of Uniaxial Compression of Single Grains

Tests of the uniaxial compression of single grains were performed in a specially designed press, which allowed the recording of an applied load in regard to the time and observation of occurring phenomena in a polarization assay. Three types of grains were tested: quartz sand, glass granules, and crushed glass. The strength tests showed different mechanisms of grain damage depending on the type of grain. In addition, the formation and spread of interference fringes, forming “chains of force” in samples with a large number of grains, were observed by testing glass grains under the polarization assay. A more detailed understanding of the strength characteristics of single grains will allow the verification of the models most commonly used in DEM.

Development of a Diamond Composite in the NI-CO-FE3P-SN-WC System Via Free Sintering for Use in Multi-Find Diamond Pearls

Objective: The main objective of this study is to manufacture a diamond composite with a metallic matrix based on Ni-Co-Fe3P-Sn-WC, using the Free Sintering process through cold uniaxial compaction, intended for the production of pearls for diamond wire saws, used in cutting ornamental stones. Theoretical Framework: The multi-wire technology represents an advancement in cutting ornamental stone blocks, allowing the simultaneous production of multiple slabs. Powder metallurgy is the predominant technique used in the manufacturing of pearls for diamond wire saws. Through testing, including scanning electron microscopy (SEM) and shear tests, it is possible to evaluate the alloy's strength, diamond crystal adhesion, and failure behavior of the alloy. Methodology: The adopted methodology involves the processing and characterization of pearls for diamond wire saws, following the techniques of powder metallurgy. Initially, parametric calculations were performed using Excel, providing a basis for subsequent analyses. Diamond-coated pearls were produced with different proportions of constituent elements, and uniaxial compressive strength tests and microstructural characterization were conducted to evaluate the results. Results and Discussion: In the adhesion tests to the metal tube, the pearls produced with the NICOFE alloy showed similar performance to the commercial pearls "A" and "B," with satisfactory direct shear strength values. However, some point defects were observed, such as porosity in the transition zone, creating a weaker bond, negatively impacting the final strength of the composite. Analysis of the commercial samples indicated that diamond abrasion was not related to the composition of the sintered alloy. Research Implications: This research suggests significant economic and technological implications, such as the development and nationalization of technology for the ornamental stone industry. The use of the NICOFE alloy could strengthen the local industry by providing a viable and more accessible alternative for the production of diamond pearls. Originality/Value: The NICOFE blend presents technical advantages for manufacturing diamond wire pearls, highlighting the environmental benefits from reduced cobalt use and economic advantages by offering more accessible materials for the ornamental stone industry.

Study on the Influence of Density and Water–Cement Ratio on the Cement Utilization, Fluidity, Mechanical Properties, and Water Absorption of Foam Concrete

In this paper, we study the influence of density and the water–cement (W/C) ratio on the slurry fluidity, compressive strength, and water absorption of foamed concrete (FC) and its mechanism of action, with the aim of proposing an optimal mix ratio for FC to reduce cement usage and carbon emissions in the construction industry and ensure the good overall performance of FC. In this experiment, two groups of experiments were designed using the control variable method. Fluidity and uniaxial compression tests showed that when the density was 600 kg/m3 and the W/C ratio was 0.6, the FC slurry had maximum fluidity, but its mechanical properties were poor and it collapsed easily. Conversely, by analyzing the uniaxial compressive strength/cement (UCS/C) ratio, it was observed that the mix ratio had a maximum cement utilization rate (W/C ratio) of 0.5 and a density of 1000 kg/m3. Nondestructive testing methods were used to measure the ultrasonic pulse velocity (UPV) and rebound value of the FC test block, and the strength and durability of FC were analyzed. The water absorption rate of the FC test block was tested, and the final analysis showed that the optimal mix ratio of FC in this test was W/C = 0.5, with a density of 1000 kg/m3.

Experimental and theoretical model study on grouting reinforcement effect of fractured rock mass

The mechanical properties of fractured rock mass have an important influence on the safety and stability of underground engineering. Grouting is a common way to reinforce fractured rock mass. The uniaxial compression tests of red sandstone specimens with different prefabricated crack inclination angles before and after grouting were carried out. Based on the load-deformation data and synchronous image acquisition, the mechanical properties, crack propagation law and failure mode of the specimens before and after grouting were studied. The results show that the peak strength and elastic modulus of the ungrouted specimen increase with the increase of the inclination angle of the prefabricated crack. Compared with the ungrouted specimen, grouting can significantly improve the peak strength and elastic modulus of the specimen. The cracks of the ungrouted specimen mainly initiate from the tip of the prefabricated crack, and the cracks of the grouting specimen mainly initiate from the upper and lower surfaces of the specimen and the far field. Based on the macroscopic and microscopic damage theory, the constitutive model of grouting rock mass is proposed. By comparing with the experimental data, the rationality of the constitutive model is verified.

Mechanical properties and damage plastic model for cement-soil mortar: Laboratory tests and numerical analysis

Cement-soil mortar is a composite material that provides an efficient and cost-effective solution for a wide range of construction applications. This study analyzes the mechanical properties of cement-soil mortar through experimental investigation and explores the application and parameter calibration of the Concrete Damage Plasticity (CDP) model in the finite element simulation of cement-soil mortar. Additionally, an innovative Initial Defect Generation (IDG) method is proposed to enhance the accuracy in simulation of failure mode. The research findings provide a simulation framework that balances simplicity and accuracy for cement-soil mortar. Uniaxial compressive tests are first conducted on cement-soil mortar specimens with water contents ranging from 40 % to 70 %, and cement-to-soil proportions from 30 % to 300 %. Based on the experimental results, the regression relationships correlating unconfined compressive strength (UCS) with elastic modulus, peak strain and stress-strain curves are established. Then, the simplified equations for calculating CDP model parameters from the UCS of cement-soil mortar are further proposed following damage mechanics. A parameter table summarizing the calculation methods for all relevant CDP parameters is provided to streamline the model calibration process. Simulations incorporating the simplified calibration method and IDG method successfully replicated the stress-strain responses and failure modes observed in uniaxial compressive strength tests of cement-soil specimens with varied strength. The results demonstrate the reliability and broad applicability of this simulation framework in predicting the mechanical performance of cement-soil mortar.

Investigation of dynamic impact behavior of bighorn sheep horn

The horn of the bighorn sheep is composed of keratin-based biological material that has a tubule-lamella structure, which gives it anisotropic hardening properties under impact loading. This paper aims to investigate the energy dissipation mechanisms inherent in bighorn sheep horns by developing a numerical material model that accounts for the horn’s anisotropic features and strain-rate effects. To this end, a transversely isotropic constitutive model, which includes both anisotropic hardening and strain-rate effects, was formulated to accurately predict the mechanical behavior of bighorn sheep horns. Material characterization was conducted through uniaxial compression tests that were conducted under quasi-static and dynamic conditions. The developed constitutive model was implemented into LS-Dyna via a user-defined material subroutine and was validated against empirical data. The validated numerical model was used to investigate the horn’s mechanical responses under dynamic loading conditions. The paper focused on impact energy dissipation mechanisms, including energy absorption and transition, stress distribution, and displacement wave propagation. The insights gained from this paper are expected to significantly contribute to the development of novel artificial materials with enhanced energy absorption and impact mitigation properties.

Mechanical properties and energy evolution of outburst coal seams under different load regimes

AbstractCoal elasticity and gas expansion are important factors for coal and gas outburst. During the outburst process, the elastic strain energy of coal is mainly released from the stress region, and the gas expansion energy near the working face is larger, and it is not a continuous release process. To reveal the mechanical characteristics and energy evolution of outburst coal seam, uniaxial and triaxial compression tests were carried out on outburst coal seam samples under different loading methods. The experimental results show that the elastic characteristics become more obvious with the increase of loading rate, the peak strain increases, the elastic modulus is linearly related with the loading rate，and the overall degree of fragmentation increases with the increase of loading rate, which is consistent with the severity of macroscopic coal failure. The failure mode of coal under uniaxial compression conditions is often manifest as brittle failure. The strength characteristics of coal under different loading rates comply with the Mohr‐Coulomb criterion, and the peak strength is linearly related to the failure time and loading rate. With the increasing confining pressure causes the failure of coal samples to transition from ductile to brittle, and the failure mode develops from local shear to overall splitting. The elastic energy evolution curve is consistent with its stress‐strain curve. With the increase of confining pressure, the limiting elastic energy and peak total energy increase in a quasi‐linear manner. The accumulated limit elastic energy plays an important role in the failure of coal samples, and the macroscopic manifestation thereof is that the coal samples fail more severely under high confining pressure conditions than under low confining pressure conditions. The research results are of great significance for the comprehensive prevention and control of coal and gas outburst.

Research on coal rock parameter calibration based on discrete element method

To ensure that the discrete element model of the coal wall accurately reflects the actual cutting process of coal and rock during virtual prototype simulation of mining equipment, this study aims to expedite the development of intelligent mining machinery. Using coal samples from the 4602 working face of Yangcun Coal Mine, operated by Yanzhou Coal Mining Group, we conducted coal rock packing experiments and uniaxial compression tests to obtain the packing angle and compressive strength of the coal samples. Based on the experimental results, we designed Plackett–Burman experiments (PB experiments), steepest ascent experiments, and Box-Behnken experiments to study the influence of particle contact mechanics parameters and bonding mechanics parameters on the packing angle and compressive strength, using the packing angle and compressive strength as response variables. Our objective is to minimize the relative error between the simulated packing angle and the measured packing angle. We solved and optimized the parameter calibration model and conducted simulation calibration experiments based on the optimization results. A comparative analysis with the actual test results revealed that the maximum relative errors between the simulated and measured values for the packing angle and compressive strength were only 2.9% and 5.0%, respectively. Additionally, a discrete element model of a typical working face coal wall was established based on the parameters obtained from this calibration method. A bidirectional coupling model of the cutting process between the coal and rock was created using EDEM-RecurDyn to simulate the rigid-flexible coupling of the coal cutter. An experimental coal wall model was constructed based on similarity theory, and both simulation and physical experiments were conducted. The evaluation metrics for comparison were the time-domain and frequency-domain characteristics of the drum’s vibration signals. The maximum relative error for the time-domain signal characteristics between the two experimental setups was only 4.19%, while the maximum relative error for the frequency-domain signal characteristics was 3.75%. This validates the feasibility of the proposed calibration method for the discrete element coal wall model and the accuracy of the calibration results. Furthermore, it demonstrates that the constructed discrete element coal wall accurately represents the actual coal and rock properties. The virtual simulation based on this model effectively replicates the interaction process between mining machinery and coal, providing a safe, efficient, and low-cost technological approach for performance analysis of mining equipment and intelligent control of supporting devices.

Quantifying sandstone crack extension and expansion via deep learning methods

This study investigates the damage evolution of sandstone under loading stresses, which can lead to irreversible plastic deformation and reduced project stability service life. To achieve this objective, we identify and quantify the emergence and expansion process of sandstone cracks using deep learning methods. Specifically, our approach employs a crack segmentation model enhanced by an attention mechanism, achieving a remarkable effective crack detection MIoU of 93.38. Through the application of connectivity domain analysis, skeleton extraction, and orthogonal projection techniques, we extract crucial crack parameters, which are subsequently formulated into equations to determine their actual dimensions. These evolving parameter variations serve as the foundation for predicting the sandstone's entire damage progression, encompassing both microscopic crack growth and eventual catastrophic failure preceding macroscopic manifestation of damage. Validation of our method through uniaxial compression tests on sandstone specimens confirm its efficacy and practical applicability. In conclusion, this study presents a novel framework for quantifying sandstone crack evolution, providing invaluable insights into the intricate mechanisms governing damage fracture progression in rocks.

Study on the pore structure of eco-regenerated mortar using corn cob based on nuclear magnetic resonance

This study aims to investigate the influence of corn cob particles on pore structure of mortar. By using NMR technology, the pore parameters of fast-hardening sulfoaluminate cement mortar (SAC) and ordinary Portland cement mortar (PO) were measured and compared. The influence of corncob particles on the mechanical properties of eco-mortar was evaluated by uniaxial compression test. The results indicate that medium and large pores of both SAC and PO increases with corn cob particle, as well as the porosity. The fractal dimensions of harmful and multiple harmful pores are negatively correlated with the volume fraction of corn cob particles. The addition of corn cob particles reduced the overall fractal dimension of the mortar and decreased the complexity of internal pores. The probability density function of grayscale values transitions from being “thin and tall” to “short and wide”, with an increasing proportion of high grayscale values. This leads to an increase in the proportion of large pores within the mortar, resulting in a continuous deterioration of pore structure. The addition of corn cob particles greatly reduces the strength of SAC and PO, but the peak stress of SAC is higher than that of PO. When corn cob particle content is 30wt% and 50wt%, the peak stress of SAC is increased by 23.37% and 14.25%, respectively, compared with the peak stress of PO.

Study on the impact of grouting reinforcement on the mechanical behavior of non-penetrating fracture sandstone

The grouting reinforcement technology is an essential method to enhance the mechanical performance of fractured rock masses and the effectiveness of reinforcement varies with different grouting materials. To further understand the mechanical improvement capabilities of each grout and the reinforcement mechanisms at the grout-rock interface, this study prepared samples with different grouting materials (sulphoaluminate cement (SAC), ultra-fine cement (UFC), and epoxy resin (EPR)) and the uniaxial compression tests were conducted. Based on these tests, the macro and micro mechanical characteristics of different grouting samples were revealed using particle image velocimetry (PIV), acoustic emission (AE), scanning electron microscopy (SEM), and nuclear magnetic resonance (NMR). The results indicate that grouting helps improve the mechanical performance and deformation resistance of fractured rock masses. It effectively limited lateral displacement of the samples, reduced stress concentration at fracture tips, enhanced shear effects during sample fracture, and altered the crack propagation process and failure modes. Compared to the fractured samples, the peak strength of SAC, UFC, and EPR samples increased by 17.8 %, 23.4 %, and 28.3 %, and the elastic modulus increased by 14.3 %, 7.9 %, and 24.8 %, respectively. Among these, the EPR samples exhibited a similarity in parameter indicators to intact samples of over 85 %, making EPR the optimal grouting material. The degree of grout-rock fusion is the primary factor influencing grouting reinforcement effectiveness. SAC is covering-type cement, UFC is embedded cement, EPR is a fusion material, and the fusion-type materials are more beneficial for improving the mechanical performance of fractured rocks.

The effect of different additives on bacteria adsorption, compressive strength and ammonia removal for MICP

Abstract Microbial induced calcite precipitation is a commonly used technique for the application of biocementation. The metabolism of urea by ureolytic active bacteria leads, among other metabolic products such as ammonium, to carbonate ions. In the presence of calcium ions, calcium carbonate formation occurs. It was investigated whether the addition of different additives (Ca-bentonite, Na-bentonite, clinoptilolite, natrolite, limestone, marl clay, concresol, secursol, and activated carbon powder) can optimize this process. First, the influence of these additives on the adsorption rates and distribution of the ureolytic active organism Sporosarcina pasteurii in quartz sand columns was tested. Moreover, an investigation was conducted on the impact of various additives on ammonium immobilization to mitigate its leaching from soils subjected to the biocementation process. For eight additives uniaxial compressive strength tests in quartz sand columns and a storage method according to DIN EN 12390–2 were carried out. Each additive showed a characteristic adsorption and localisation progression. Furthermore, each additive was able to enhance the immobilization behavior of the present ammonium, with a maximum immobilization capacity of 10.76 $$\frac{mg (NH^+_4)}{g (additive)}$$ m g ( N H 4 + ) g ( a d d i t i v e ) . The uniaxial compressive strength of biocemented columns out of quartz sand could sectionally be increased by the addition of each additive. However, the storage methodology shows a much greater influence on column strength. Overall, the best results were achieved with the two additives, Ca-bentonite and clinoptilolite, resulting in strength increases in sand columns of up to 4.64 and 3.22 $$\frac{N}{mm^2}$$ N m m 2 , respectively.