Biopolymer treatment of geomaterials is a promising technology with green technology potential that can help reduce global warming. It offers a positive environmental impact and a wide range of applications. This paper reports the results of a study of the mechanical performance of biopolymer-treated dune-sand from the Algeria desert. The sand was mixed with varying amounts of xanthan gum biopolymer and reinforced with polypropylene fibre. The study demonstrated that xanthan gum treatment improved the Unconfined Compressive Strength (UCS) of unreinforced sand and fibre-reinforced sand. Nonetheless, the test results revealed that biopolymer-treated sand manifested higher resistance after drying. Based on the findings, the optimal quantity of xanthan gum for treating sand is 2%. The incorporation of fibre in the matrix increases the strength and failure strain. The Scanning Electron Microscopy (SEM) analysis further substantiated that the biopolymer bonds the sand particles together and the distribution of PP fibre in the mixture, thereby enhancing compressive strength and durability. The results indicate that using xanthan gum biopolymer treatment offers an environmentally friendly approach to enhancing the mechanical properties of desert sand.

The most significant soil parameters that are utilized in geotechnical engineering projects' design and implementations are soil strength parameters including friction (ϕ), cohesion (c), and uniaxial compressive strength (UCS). Understanding soil shear strength parameters can be guaranteed the design success and stability of structures. In this regard, professionals always looking for ways to get more accurate estimations. The presented study attempted to investigate soil shear strength parameters by using multivariate regression and multilayer perceptron predictive models which were implemented on 100 specimens' data collected from the Tabriz region (NW of Iran). The uniaxial (UCS), liquid limit (LL), plasticity index (PI), density (γ), percentage of fine-grains (pass #200), and sand (pass #4) which are used as input parameters of analysis and shear strength parameters predictions. A confusion matrix was used to validate the testing and training data which is controlled by the coefficient of determination (R²), mean absolute (MAE), mean squared (MSE), and root mean square (RMSE) errors. The results of this study indicated that MLP is able to predict the soil shear strength parameters with an accuracy of about 93.00% and precision of about 93.5%. In the meantime, the estimated error rate is MAE = 2.0231, MSE = 2.0131, and RMSE = 2.2030. Additionally, R² is evaluated for predicted and measured values correlation for friction angle, cohesion, and UCS are 0.914, 0.975, and 0.964 in the training dataset which is considerable.

Traffic-induced cyclic loading leads to the rotation of principal stresses within pavement foundations, challenging accurate simulation with conventional triaxial testing equipment. To investigate the deformation characteristics of fiber-reinforced soil under traffic loads and to develop a fractional-order model to describe these deformations. A series of hollow cylinder torsional shear tests were conducted using the GDS-SSHCA apparatus. The effects of fiber content, load frequency, cyclic deviatoric stress amplitude, and cyclic shear stress amplitude on soil deformation were analyzed. The results revealed that fiber content up to 3% enhances soil resistance to deformation, while higher fiber content reduces it. Axial cumulative plastic deformation decreases with higher load frequencies and increases with higher cyclic stresses. The study also found that principal stress rotation exacerbates soil deformation. A fractional integral model based on the Riemann-Liouville operator was developed to describe the axial cumulative plastic strain, with its validity confirmed by supplementary tests. This model provides a scientific basis for understanding foundation deformation under traffic loading and contributes to the development of dynamic constitutive soil models.

In the present study, the acoustic emission characteristics of hard sedimentary sandstone with varying bedding dip angles were examined through uniaxial compression tests using a rock mechanics creep apparatus combined with an acoustic emission system. The deformation and failure behavior of the sandstone was analyzed by correlating acoustic emission parameters with stress over time. A damage constitutive model was developed, incorporating cumulative acoustic emission ringing counts as a key parameter, with time acting as the intermediary. The findings indicate that, despite the differences in bedding dip angles, the stress-strain curves of the samples follow a similar pattern throughout the loading process, passing through four distinct phases: compaction, elastic deformation, yielding, and post-peak failure. The fracture patterns of the sandstone are influenced by the dip angle of the bedding. Acoustic emission parameters, including the ringing count, cumulative ringing count, and energy, align with these four stages of the stress-strain curve. During the compaction and elastic deformation phases, acoustic emissions remain in a quite state, with only brief spikes at points of rapid stress change. In the unstable fracture stage, acoustic emissions become highly active, while they return to a quite state in the post-fracture stage. The RA value of the acoustic emission displays a banded pattern as time progresses, with areas of dense clustering. When the stress curve declines, RA values enter an active period, mainly associated with the generation of shear cracks. Conversely, during periods of smooth stress progression, RA values remain in a quiet state, primarily linked to the formation of tensile cracks. The time-based damage constitutive model for layered sandstone effectively captures the entire process of rock fracture development.

Gravity wall combined with anchoring frame beam is widely adopted to support a high slope under complex geomorphic condition, in which the rigid gravity wall is adopted as a lower structure and the flexible anchoring frame beam serves as an upper structure. The seismic anchor force and the seismic active earth pressure are two essential issues for the seismic design of combined retaining structure in high seismic intensity area. In this study, an analytical model of combined retaining structure is established based on the upper bound theorem of limit analysis, and the formulas for seismic anchor force and seismic active earth pressure of combined retaining structure are derived. The results are optimized by using the global optimization algorithm. The proposed method is verified by a comparison with previous method. Moreover, the influence of main parameters on seismic anchor force and seismic active earth pressure is analyzed to facilitate the seismic design of such combined retaining structure.

Existing piles, especially in urban areas, are at risk of being cut by new tunnel construction, potentially affecting their serviceability. This study examined the behaviour of piles under various reinforcement conditions subject to tip cutting resulting from tunnel excavation. For this, the construction of a tunnel using a shield tunnel boring machine adjacent to existing single and group piles was simulated. A three-dimensional finite element analysis was used to perform the simulations. Certain piles in the group were simulated by cutting the pile tips to mimic the effect of tunnel excavation, and the behaviour of the piles was studied by considering the effect of pile cap and ground reinforcements. A numerical analysis was used to examine the ground settlement caused by tunnel excavation, pile head settlement, axial pile force, and shear stress occurring at the pile-ground interface. The results revealed that for all piles with pile tips supported by weathered rock, the shear stress distributions demonstrated similar trends, whereas for piles with cut tips, tensile or compressive forces occurred simultaneously according to the relative position by pile depth. Additionally, when the pile tip was supported by weathered rock, approximately 70% of the support was due to shaft friction and the remaining 30% was provided by the pile tip. For piles without reinforcement, the final settlement was approximately 70% greater than that of piles with grouting reinforcement. These results indicate that pile and ground settlements are substantially influenced by pile tip cutting and reinforcement conditions.

This paper investigated the deformation of a large-diameter pipeline caused by double shield tunnel construction in silty fine sand strata in Nantong, China, by on-site measurements and numerical simulations. Results indicate the pipe settlement curve was not symmetrical after the double tunnel construction in the silty fine sand strata. The construction of the subsequent tunnel had a significantly smaller impact on the stress and horizontal displacement of the pipeline than the preceding tunnel. There is a significant shading effect of the large-diameter pipeline, which would restrict the soil settlement above the pipeline. The adjusted settlement formula shows good agreement with the measured data, facilitating approximate calculations for both surface and pipe settlements. The correction factor a ranges from 0.50 to 0.90, while b ranges from 0.95 to 1.20.The elastic modulus and the burial depth of the pipeline had a great effect on the stress of the pipeline, but a smaller effect on its settlement. However, the soil loss rate greatly affected both the settlement and stress of the pipeline. Moreover, the pipeline risk level distribution map can quickly identify the risk status of the pipeline.