The nonlinear mechanical behaviour of pipeline joints influences the seismic response of water supply pipelines. This study presents an experimental investigation of the tensile behaviour of push-on joints of ductile iron (DI) pipelines, subjected to axial tensile forces and internal water pressure. The axial performance and damage states of joints are determined for push-on joints with different diameters. A statistical analysis is then conducted to determine the correlation between tensile strength and joint opening. An empirical equation for estimating the tensile strength of pipeline joints is proposed, along with a normalized failure criterion for joint opening considering water leakage. Moreover, a numerical model for buried pipelines considering nonlinear soil-pipe interaction is developed. Incremental dynamic analysis (IDA) is performed on DI pipelines with explicit consideration of the uncertainty of joint mechanical properties. Seismic fragility curves are developed based on the IDA results. The effect of mechanical parameter uncertainty of pipeline joints on seismic risk assessment of segmented pipelines is quantitatively evaluated. The numerical results indicated that the failure probability of the pipeline considering the uncertainty of joint mechanical properties is approximately 1.5 to 2 times larger than that predicted by a deterministic model.

Geosynthetics are widely used in reinforced soil engineering because of their excellent performance. Currently, an increasing number of researchers are studying the fabrication of geosynthetics with both reinforcement functions and sensing abilities. Sensor-enabled piezoelectric geobelts (SPGBs) have great potential in the field of integrated soil reinforcement monitoring because of their ability to reinforce and sense soil. In this paper, polymer-based SPGBs that can be batch extruded were successfully prepared using high-density polyethylene (HDPE), polyolefin elastomer (POE), carbon black (CB), and piezoelectric ceramics (PZT), and the preparation rate of SPGBs was substantially improved. Laboratory tensile tests were conducted to test the strain-stress-impedance-voltage signals of SPGB in the tensile process at 45 different ratios. The results showed that the piezoelectric strain constant (d33) of SPGBs was up to 10.5 pC/N. The tensile strength and breaking strain of SPGBs reached their maximum values of 14 MPa and 26.37%, respectively, at 65% PZT content. During the tensile test, the SPGB normalized impedance increased with increasing strain, and there was a significant sudden increase at the time of damage. An empirical formula for strain-normalized impedance, which can be used to calculate the strain of SPGBs quantitatively, was established. The SPGB output voltage rapidly increased and then decreased with increasing strain, and two characteristic points can be used as warning signs to qualitatively describe the change of SPGBs. The results of this study can provide a design basis for the batch preparation of SPGBs in engineering.

Soil tensile strength is a critical parameter governing the initiation and propagation of tensile cracking. This study proposes an eco-friendly approach to improve the tensile behavior and crack resistance of clayey soils. To validate the feasibility and efficacy of the proposed approach, direct tensile tests were employed to determine the tensile strength of the compacted soil with different W-OH treatment concentrations and water contents. Desiccation tests were also performed to evaluate the effectiveness of W-OH treatment in enhancing soil tensile cracking resistance. During this period, the effects of W-OH treatment concentration and water content on tensile properties, soil suction and microstructure were investigated. The tensile tests reveal that W-OH treatment has a significant impact on the tensile strength and failure mode of the soil, which not only effectively enhances the tensile strength and failure displacement, but also changes the brittle failure behavior into a more ductile quasi-brittle failure behavior. The suction measurements and mercury intrusion porosimetry (MIP) tests show that W-OH treatment can slightly reduce soil suction by affecting skeleton structure and increasing macropores. Combined with the microstructural analysis, it becomes evident that the significant improvement in soil tensile behavior through W-OH treatment is mainly attributed to the W-OH gel's ability to provide additional binding force for bridging and encapsulating the soil particles. Moreover, desiccation tests demonstrate that W-OH treatment can significantly reduce or even inhibit the formation of soil tensile cracking. With the increase of W-OH treatment concentration, the surface crack ratio and total crack length are significantly reduced. This study enhances a fundamental understanding of eco-polymer impacts on soil mechanical properties and provides valuable insight into their potential application for improving soil crack resistance. (c) 2024 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/).

The current study focuses on the degradation rate of polypropylene (PP) and Bauhinia Vahlii (BV) fibers under soil burial and natural weathering conditions for 360 days. The BV-PP composite was produced with varying BV fiber compositions (0, 10, 20, and 30 wt.%) and 3 % MAPP (Maleic Anhydride Grafted Polypropylene). In addition, MAPP is employed as a coupling agent to improve fiber-matrix compatibility and promote degradation. The XRD examination shows that a 10 % BV-PP composite has a crystallinity index of 52.05 %, which is higher than that of neat PP. The rate of biodegradability was investigated using weight loss and tensile properties. The largest degradation was seen in natural weathering conditions with 30 % composite showing the maximum weight loss of 3.8 % and loss in tensile strength and modulus of 16.76 % and 5.11 %, respectively. Simultaneously, no weight loss or drop in tensile characteristics was found in the case of neat PP over 360 days. The SEM images of soil burial show material deterioration, which may be aided by bacterial and fungal activity, whereas natural weathering conditions show a large crack, rougher fracture surface, and cavities, which are attributed to thermal stresses, changes in moisture content, and ultraviolet radiation, thereby promoting the degradation process. The current study focuses on the degradation rate of composite consisting of polypropylene (PP) and Bauhinia Vahlii (BV) fibers under soil burial and natural weathering conditions for 360days. The composites with 30 % BV content exhibited the highest degree of weight change and reduction in tensile properties when subjected to natural weathering conditions, followed by the soil burial method. image

A multifunctional biodegradable additive powder has been created for simultaneous enhancement of toughness and compostability of the biopolymer poly(lactic acid) (PLA). PLA has promising strength and stiffness compared to commodity plastics, but the neat polymer is not a direct replacement for petroleum-based plastics in consumer products due to its brittle fracture and low ductility. Although officially certified as biodegradable, PLA suffers from a slow composting rate and is not considered compostable outside of specialized environments such as those found in industrial composters (where temperatures approaching 60 degrees C are used). A powder-based additive has been developed that increases both the elongation at break and the composting rate of PLA to enhance the attractiveness of PLA over current commodity plastics. In this study, various amounts of the additive are compounded into PLA using a single screw extruder. Test specimens are prepared using the additive manufacturing method of fused filament fabrication. The PLA-based composites show a minimal loss of strength and stiffness as compared to plasticized PLA resins, and the additives provide tunable properties to the material in the ability to control elongation versus strength and stiffness. Direct tensile testing of 3.75 mm filament for additive manufacturing to compare material properties is also investigated. The composting behavior is investigated using specimens made by extrusion as part of an additive manufacturing model system. Composting studies show an increase in composting rate under elevated temperature of 58 degrees C and 50 % relative humidity under modified ASTM D5338 soil contact testing. Microbial analysis indicates that the additive particles support the growth of specific degraders and shifts the composition of the microbial population of bacteria and fungi and has potential for enhancing the compostability in home compost.

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.

Ferronickel slag is the solid waste slag produced by smelting nickel-iron alloy. After grinding ferronickel slag into powder, it has potential chemical activity. It can partially replace cement and reduce the amount of cement, and is conducive to environmental protection. The mechanical properties of soil cement were investigated through the compressive strength test and inter-split tensile test of ferronickel slag powder soil cement with different dosages. To further study the mechanism of ferronickel slag powder's action on soil cement microscopically, the microstructure of soil cement was analyzed by using a scanning electron microscope and nuclear magnetic resonance equipment. The results of the study show that the incorporation of ferronickel slag powder can enhance the compressive and tensile strength of soil cement. The best performance enhancement of ferronickel slag powder was achieved when it was doped with 45% of its mass. The hydration products of soil cement increased with the increase in the doping amount, but the excessive doping of ferronickel slag powder would lead to a weakening of the hydration reaction and a decrease in the strength of the soil cement. At the same time, ferronickel slag powder plays the role of filling the void of soil cement. With the increase in ferronickel slag powder, the large pores inside the soil cement are reduced and the structure is denser.

In this paper, a triple large-scale biaxial tensile test system for geosynthetics developed by the authors was used to study the tensile mechanical properties of warp-knitted polyester (PET) geogrids. In-isolation tensile (in air) tests with various strain rates were conducted to investigate the effects of tensile modes (uniaxial and biaxial tension) on the tensile mechanical properties of warp-knitted PET geogrids. To evaluate the influences of normal stress and confined soil types (sand and gravel) on the tensile load-strain characteristics of warp-knitted PET geogrids under uniaxial and biaxial tensile loading, strain rate-controlled tensile tests in soil were also carried out. The results demonstrated that the low strain rate leads to low tensile load and secant tensile stiffness of geogrids in-isolation tensile tests. The biaxial in-isolation tensile tests mobilized a lower tensile load throughout the tensile process. The constraint of soil types and the application of normal stress increased the tensile load and secant tensile stiffness of geogrids. In general, the confined soil reduces the impact of uniaxial and biaxial tensile loading on the tensile tests. Geogrids embedded in sandy soils showed improved mechanical properties.

The tensile strength at the rock-concrete interface is one of the crucial factors controlling the failure mechanisms of structures, such as concrete gravity dams. Despite the critical importance of the failure mechanism and tensile strength of rock-concrete interfaces, understanding of these factors remains very limited. This study investigated the tensile strength and fracturing processes at rock-mortar interfaces subjected to direct and indirect tensile loadings. Digital image correlation (DIC) and acoustic emission (AE) techniques were used to monitor the failure mechanisms of specimens subjected to direct tension and indirect loading (Brazilian tests). The results indicated that the direct tensile strength of the rockmortar specimens was lower than their indirect tensile strength, with a direct/indirect tensile strength ratio of 65%. DIC strain field data and moment tensor inversions (MTI) of AE events indicated that a significant number of shear microcracks occurred in the specimens subjected to the Brazilian test. The presence of these shear microcracks, which require more energy to break, resulted in a higher tensile strength during the Brazilian tests. In contrast, microcracks were predominantly tensile in specimens subjected to direct tension, leading to a lower tensile strength. Spatiotemporal monitoring of the cracking processes in the rock-mortar interfaces revealed that they show AE precursors before failure under the Brazilian test, whereas they show a minimal number of AE events before failure under direct tension. Due to different microcracking mechanisms, specimens tested under Brazilian tests showed lower roughness with flatter fracture surfaces than those tested under direct tension with jagged and rough fracture surfaces. The results of this study shed light on better understanding the micromechanics of damage in the rock-concrete interfaces for a safer design of engineering structures. (c) 2024 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/).