In unsaturated soil mechanics, the liquid bridge force is a significant source of soil cohesion and tensile strength. However, the classical Young-Laplace equation, which neglects the stratified nature of water at the nanoscale, fails to accurately capture the physical and mechanical behaviour of nanoscale liquid bridges. This study utilizes molecular dynamics simulations to investigate the wetting behaviour and mechanical mechanisms of liquid bridges between particles at the nanoscale. The study proposes dividing the liquid bridge force into three components: surface tension, matric suction, and adsorption force, to explain the mechanics of nanoscale liquid bridges more comprehensively. The results demonstrate that water layers within liquid bridges exhibit discrete stratified structures at the nanoscale. Moreover, the mechanical behaviour of liquid bridges is highly dependent on pore water volume and pore spacing. Specifically, the contact angle is positively correlated with the pore spacing, while the liquid bridge force increases with the pore water volume and is inversely proportional to the pore spacing. As the separation distance increases, the liquid bridge force gradually diminishes until rupture occurs. This research expands the applicability of the classical Young-Laplace equation and offers new insights into the mechanical properties of unsaturated soils, particularly clays.

The NT-CEP pile is an innovative type of pile that builds upon the conventional concrete straight-hole cast-in-place pile. It primarily consists of two components: the main pile and the bearing plate. The key factors influencing its load-bearing capacity include the pile diameter, the cantilever dimensions of the bearing plate, and the slope of the bearing plate's foot, among others. The pile spacing significantly influences the bearing capacity of NT-CEP pile group foundations. The overall bearing capacity of an NT-CEP pile group foundation is not merely the sum of the ultimate bearing capacities of individual piles; rather, it results from the interactions among the pile bodies, the cap, and the foundation soil. Advancing the design theory of NT-CEP pile groups and enhancing their practical applications in engineering requires an in-depth investigation of how different pile spacings influence the load-bearing performance of pile group foundations. This objective can be achieved by exploring the soil damage mechanisms around side, corner, and central piles. This exploration helps in clarifying the influence of pile spacing on the load-bearing performance. Based on research findings regarding the bearing capacity of single and double pile foundations, this paper utilizes ANSYS finite element simulation analysis to model six-pile and nine-pile groups. Because these arrangements are universally adopted in engineering practice, they are capable of accounting for the pile group effect under various pile spacings and row configurations. The nine-pile group comprises corner piles, side piles, and a center pile, enabling a comprehensive analysis of stress variations among piles at different positions. As six-pile and nine-pile groups represent common pile configurations, studying these two types can provide valuable insights and direct references for optimizing pile foundation design. The study systematically investigates the influence of varying piles spacings on the bearing capacity of NT-CEP pile group foundations. It concludes that, as pile spacing decreases, The displacement of the top of this pile increases. thereby enhancing the group piles effects. Conversely, increasing the spacing between piles represents an effective strategy for elevating the compressive capacity of the NT-CEP pile-group foundation. Larger spacing also increases the vertical load-bearing capacity of the central piles, enhances the lateral friction resistance of corner piles, and heightens the load-sharing proportion between the bearing plate and the pile end. Furthermore, increasing pile spacing raises the ratio of load sharing by the foundation soil for both the CEP nine-pile foundation and the CEP six-pile foundation. The reliability of the simulation study has been verified by a visualization small scale model test of a half cut pile.

The existing mechanical and grouting anchors mostly use the expansion shell method to form a cavity on the borehole wall, and the cement slurry is poured to form multiple enlarged head plates, but the operation is more difficult and the diameter of the formed plate is smaller. In this paper, a new type of large-diameter multi-plate soil anchor and its reaming cavity forming tool are proposed, which can make the operation easier and form a large-diameter enlarged head plate. In order to study the influence of the diameter of anchor plate, the number of anchor plates and the spacing of anchor plates on the vertical uplift capacity of the large-diameter multi-plate soil anchor, 25 sets of comparative models were established for simulation analysis. The finite difference method of FLAC(3D) software is used to simulate the model. It is found that when the length of the anchor is 6 m and the diameter of the anchor rod body is 150 mm, the optimal diameter of the anchor plate of the large diameter multi-plate soil anchor is 590 mm, the optimal number of anchor plates is 6, and the optimal anchor plate spacing is 800 mm, which means the action range of the anchor plate on the lower soil is about 5 times the diameter of the bolt. When the number of anchor plates is too small or the spacing between anchor plates is too large, the structural advantages of large-diameter multi-plate soil anchor cannot be fully utilized, resulting in a decrease in the ultimate uplift capacity. When the number of anchor plates is too large or the spacing between anchor plates is too small, the stress superposition effect occurs in the soil, and the through shear failure occurs, which leads to the decline of the ultimate uplift capacity. Under the condition that the number of anchor plates and the spacing of anchor plates are fixed, the larger the diameter of the anchor plate is, the larger the ultimate pull-out capacity of the large-diameter multi-plate soil anchor is, the smaller the vertical failure displacement of the anchor head is, but the increase of the uplift capacity is gradually reduced. The creep rate of the new large-diameter multi-plate soil anchor bolt is 0.91 mm, and the creep rate of equal-diameter soil anchor bolt is 1.69 mm. It is verified that the new large-diameter multi-plate soil anchor can be effectively applied to various projects.

This study investigates the impact of nearby structures on the cyclic settlement mechanisms of shallow foundations in liquefiable soils using a numerical model based on Biot's porous media theory. The model predicts excess pore water pressure and settlement by coupling equilibrium and continuity equations, solved using an implicit time integration scheme. Soil nonlinearity under cyclic loading is represented using generalized plasticity, boundary surfaces, and non-associated models. Three scenarios are simulated to study the effect of spacing between light and heavy foundations and variation in acceleration intensity. Results show that as spacing between foundations increases, lateral displacement and settlement decrease. Excess pore water pressure generation also decreases with increased foundation spacing. Soil just below the foundation exhibits maximum settlement, decreasing with depth. When input acceleration increases from 0.1 g to 0.15 g and 0.2 g, settlement increases by 40%-55% and 90%-110% respectively for both light and heavy foundations, regardless of spacing. Excess pore water pressure also increases sharply with higher acceleration intensity. The findings highlight the importance of considering foundation-soil-foundation interaction effects in liquefaction-prone urban settings and provide insights for designing resilient shallow foundations. The advanced numerical modeling approach offers engineers a more informed way to mitigate liquefaction risk and build safer, more durable structures in earthquake-prone areas.

Micropile groups (MPGs) are typical landslide resistant structures. To investigate the effects of these two factors on the micropile-soil interaction mechanism, seven sets of transparent soil model experiments were conducted on miniature cluster piles. The soil was scanned and photographed, and the particle image velocimetry (PIV) technique was used to obtain the deformation characteristics of the pile and soil during lateral loading. The spatial distribution information of the soil behind the pile was obtained by a 3D reconstruction program. The results showed that a sufficient roughness of the pile surface was a necessary condition for the formation of a soil arch. If the surface of the pile was smooth, stable arch foundation formation was difficult. When the roughness of the pile surface increases, the soil arch range behind the pile and the load-sharing ratio of the pile and soil will increase. After the roughness reaches a certain level, the above indicators hardly change. Pile spacing within the range of 5-7 d (pile diameters) was suitable. The support effect was poor when the pile spacing was too large. No stable soil arch can be formed, and the soil slips out from between the piles.

The technology of expansion fracturing with liquid CO2 (EFLCO2) has attracted increasing attention due to reduced vibration and damage. The disposable fracturing tube has been developed and is gradually replacing the Cardox tube. However, there is a lack of impact pressure testing of disposable tubes under real working conditions, selection of gas explosion design parameters, and systematic analysis of blasting vibration. This limitation has constrained the widespread application of disposable fracturing tubes in engineering. A joint monitoring of the pressure-time curves in the disposable tubes and boreholes was conducted. The rock-breaking effect of varying hole spacing parameters in the EFLCO2 design was analyzed, and a systematic study was carried out on the vibration peak value, frequency, and energy characteristics. The results show that (1) the pressure distribution characteristics, stress peak value, and duration in the disposable tubes are different from those of Cardox tubes, which show multi-peak distribution, low-pressure peak value, and short duration. The correlation between the pressure in the disposable tube, filling pressure, and liquid CO2 weight is established, and a theoretical calculation method for the borehole wall pressure is proposed; (2) The hole spacing in rocks of different hardness is suggested; and (3) At the same scale distance, the peak particle velocity (PPV) caused by EFLCO2 (PPVCO2) is significantly smaller than that caused by blasting (PPVexplosive). The ratio of PPVexplosive to PPVCO2 is a power function related to scale distance, and a distance-related zonality exist in this relationship. The frequency composition of the vibration signal caused by EFLCO2 is relatively simple with a narrow frequency band. Its PPV and energy are mainly concentrated in the low-frequency band. This research contributes to the optimization of disposable fracturing tubes, gas explosion design, and vibration hazard control. (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/).

A healthy orchard necessitates well-balanced nutrition. In order to achieve a high yield, fertilizer application in the proper amount and position is important. Existing fertilizer application methods (band placement, pellet application, and ring basin method) have limitations such as excessive fertilizer application, soil acidity, nutrient imbalance, soil structure damage, bulk density rise, and more. A spot fertilizer applicator that can dispense the proper amount of fertilizer at right site can reduce fertilizer waste, lowering pollution and input costs. As a result, a novel grooved belt type metering system was designed with an autonomous plant detection-based spot fertilizer application. The fertilizer placement and consistency of amount dispensed per plant of the applicator were assessed in the lab. The independent parameters were metering belt groove volume (50, 100 and 150 cm3), metering belt speed (8, 9 and 10 m.min-1), plant spacing (45, 60, 75 and 90 cm) and forward speed (2, 2.5 and 3 km.h-1). Forward speed had a considerable impact on the band length, whereas groove volume and belt speed had a substantial impact on the lateral placement parameters. Because plant spacing had no significant effect and the means of real and measured fertilizer application amounts were equal, the machine was found suitable for applying fertilizer with any plant spacing. Using a full factorial experimental design, the optimal values for independent parameters such as groove volume, plant spacing, belt speed, and forward speed were assessed 50 cm3, 78.4 cm, 8.74 m.min-1, and 2.72 km.h-1, respectively with a high desirability of 0.971. In comparison to mechanical sensing type available spot fertilizer applicators, the developed spot fertilizer applicator required half the sensing and actuation time and had three times less fluctuation in fertilizer dosing.

Simulation and accurate modeling of the mixing process of the high-pressure jet-cutting clay by the water-air coaxial nozzle is significantly important for the performance optimization of the triple fluid jet grouting. In this paper, a numerical model considering the soil rheological properties is proposed to investigate the mixing process of the high-pressure jet-cutting clay. The cohesive force model of clay is obtained based on the solution of the power law index and consistency factor by coupling the Herschel-Bulkley and soil logarithmic models. The interaction model among the gas phase, the liquid phase, and the clay medium is further established through use of the drag force model. A laboratory device of high-pressure jet-cutting transparent clay is developed to prove the feasibility of the proposed model for the mixing process of the high-pressure jet-cutting clay. Finally, using the validated numerical model, the mixing process of the high-pressure jet-cutting clay by the water-air coaxial nozzle with varying radial spacings between the air nozzle and water nozzle is numerically investigated, and the axial stability of the jet, the width of the cross-sectional profile, and the variation of the central axis velocity field of the mixing process are analyzed. Results demonstrated that the variation trend of the jet in both simulations and experiments is consistent, and the maximum error in jet depth is better than 3.3%, validating the accuracy of the numerical model of the mixing process of the high-pressure jet-cutting clay. The optimal radial spacing size for a water-air coaxial nozzle in high-pressure jetting of clay medium is 1.4 mm, which provides the best axial stability, the narrower jet cross-section, and the slowest decay of jet velocity along the central axis.

Buckle initiation devices, such as sleepers and distributed buoyancy modules, are typically adopted to initiate lateral buckles at pre-determined locations to release thermal expansion in a controlled manner to ensure pipeline integrity. For pipelines installed by S-lay, sleepers are desired as it is difficult for buoyancy modules to pass over the stinger rollers. If the thermal cyclic fatigue is critical in the pipeline design, pipeline lateral buckling designs may result in small sleeper spacing. As such, buckle reliability of conventional sleepers may be inadequate in some cases. In this paper, lateral buckling mitigation with sleepers is investigated using finite element (FE) models for a water injection pipeline. Sensitivity analyses are performed on key input parameters including single and dual sleepers, lower bound and upper bound friction factors between sleeper and pipeline, berm effects on soil lateral resistances, and sleeper heights. Based on the sensitivity study results, a mitigation solution combining sleepers and mattresses under the pipeline touch down zones is proposed and evaluated. It is found that sleepers combined with reduced touch down point lateral friction can reduce the maximum longitudinal strain and thermal fatigue damage by more than 50% as compared to using sleepers alone as mitigation. Therefore, this design adds a new option to allow increases in the sleeper spacing and improved reliability of buckle initiation.