Cracking behaviour of silty mudstone with existing flaws can trigger slope instability. However, the mechanics of multi-fractured silty mudstone have not been adequately examined. To handle this issue, the study employs a comprehensive approach to investigate the mechanical characteristics and cracking mechanism of fractured silty mudstone combing uniaxial compression test conducted by similar material specimens, cracking strength model, macro damage model, and PFC. Similar material specimens containing prefabricated fractures are prepared using steel sheet insertion during curing. Results show that peak strength initially decreases and subsequently increases as the facture dip angle (β) increases, minimizing at 45° under uniaxial compressive load. The more fracture there exists, the greater reduction in peak strength. The failure morphology of fractured silty mudstone can be categorized into tensile failure, shear failure, and tensile-shear combined failure. Theoretical models confirm that the crack strength depends on β and fracture length (a), aligning with experimental results while crack strength exhibit inversely proportional to a. The simulation results are in good correlation with test results, verifying the reliability of the simulated approach combined with theoretical analysis. Overall, the novel contribution of this paper lies in the multilateral elucidation of the failure mechanism in silty mudstone containing multiple fractures.

Carbonaceous mudstone aggregates are prone to disintegrate to produce alkaline hydrosols under dry and wet cycles, which affects the planting performance of vegetation concrete (VC). To improve the planting performance of carbonaceous mudstone aggregate vegetation concrete (CMAVC), while considering the soaking time and concentration are the main factors influencing the effect of pH-reducing, pH reduction and performance improvement tests, uniaxial compressive tests under different soaking time and concentration were carried out, and verified by the vegetation tests and microscopic tests. The results show that ferrous sulfate and oxalic acid reduced the pH of CMAVC effectively; 0.9 mol/L ferrous sulfate and 1.2 mol/L oxalic acid are the best ratio of pH-reducing materials to ensure that the compressive strength of CMAVC is more than 5 MPa (require by the specification), which the pH values reduced by 20.4% and 29%, respectively, and after soaking 28d, the uniaxial compressive strength reduced by 9.2% from 5.64 to 5.12 Mpa and 5.7% from 5.64 to 5.32 Mpa; Moreover, the reaction of oxalic acid with calcium hydroxide, calcium carbonate, and calcium alumina produces calcium oxalate stone, which fills the internal pores of CMAVC to ensure the excellent mechanical strength and planting effect.

To investigate the effects of compaction (K), rock content (RC), and wet-dry cycle (WD) on the road performance of carbonaceous mudstone soil-rock mixtures (CMSRM), orthogonal tests were designed to measure the unconfined compressive strength (UCS) and California bearing ratio (CBR). The correlation degree of K, RC, and WD with the UCS and CBR of CMSRM was investigated using orthogonal theory and grey correlation theory. Based on multivariate nonlinear regression analysis, mathematical models of the road performance of CMSRM were built. The results show that the UCS and CBR of CMSRM were positively correlated with K and negatively correlated with the WD. With increasing RC, UCS increased at first and then decreased, while CBR increased continuously. The failure modes of CMSRM change from tensile failure to shear failure as the K increases under uniaxial compression. The RC and WD affect the structural integrity of the failed samples. Combining the results of range analysis, variance analysis, and grey relational analysis, the most significant influence on the UCS is K, and the most significant influence on the CBR is RC. It is recommended to select 94%–96% for K and 40%–60% for RC in engineering.

The paper aims to study the mechanical characteristics of disintegrated carbonaceous mudstone in a triaxial stress state from a micro-perspective of particles. Based on the discrete element method (DEM), a spherical-polymer (SP) model that includes three different types of the particles (triangle-like, rectangle-like, and sphere) was proposed and combined the error diagram with R² to analyze the difference between the SP model and Ball–Ball (BB) model. Meanwhile, a sensitive analysis of micro-mechanical characteristics was carried out, which quantitatively described the sensitivity of different parameters according to stress–strain curves. The processes of deformation and failure for the disintegrated carbonaceous mudstone were finally analyzed based on the displacement diagram of the particle according to the energy theory. The results suggest that the SP model could better reflect the mechanical characteristics of disintegrated carbonaceous mudstone, for the SP models, the correlation coefficient (R²) range was larger than the BB model. From the sensitivity analysis of parameters, the decreasing rate of initial deformation modulus was 56–66% as the stiffness ratio was modified when fixing other factors. The peak strength correlated well with the tensile-shear strength ratio, stiffness ratio, and friction coefficient. The modification of abnormal-shaped particles’ volume fraction ratio could affect the peak shear strength significantly. For the disintegrated carbonaceous mudstone, the processes of deformation and failure were discussed by energy transference which particle elements go from a low-energy state to a high-energy state.

Cryogenic extraction of water from plant and soil samples constitutes a critical element in isotope eco-hydrological studies. This study was undertaken to examine the stability and reliability of a new generation of water extraction technology based on cryogenic vacuum distillation (CVD)-automatic cryogenic vacuum distillation water extraction system, and to optimize the extraction time and improve the extraction efficiency for this system, as well as to explore the applicability of this system. For these purposes, water extraction from tap water and leaves and stems of four species of woody plants was carried out by using manual and automatic CVD systems and then the hydrogen and oxygen isotope values (δ²H and δ¹⁸O) of water extracted from the two systems were compared. Besides, rehydrated leaves, stems and soils were extracted by manual CVD system and automatic CVD system under different extraction time lengths, then the δ²H、δ¹⁸O of water extracted with the two systems were compared too. Moreover, we conducted a separate experiment to use the automatic CVD system to confirm the depth of water absorption and the utilization ratio of source water of Osmanthus fragrans (Thunb.) Loureiro. The results are as follows. There is no significant difference in the hydrogen and oxygen isotope values (δ²H, δ¹⁸O) of water extracted with the two systems and that data obtained from the two methods are strongly linearly correlated, with the correlation line being statistically indistinguishable from the 1:1 line. The δ²H and δ¹⁸O values of rehydrated sample water extracted from leaves, stems and soils for 1 h, 2 h, and 2 h by automatic CVD system are not statistically different from those extracted by manual CVD system. The depth of water uptake and the proportion of water use of Osmanthus fragrans (Thunb.) Loureiro determined based on δ²H is inconsistent with that determined based on δ¹⁸O. Therefore, this study systematically verifies for the first time that there is no difference between automatic CVD system and manual CVD system, which provides a guarantee of reliability in the related application of isotope eco-hydrology; further, this study enables us to establish recommendations on optimizing the extraction time and improving the extraction efficiency for the automatic CVD system. Meanwhile, our finding of that the δ²H of water extracted from the rehydrated samples were more depleted than the reference water adds evidence to the recently revealed phenomenon of "deuterium deviation" as caused by CVD in the ecohydrological field; as such, we suggest more caution in utilizing CVD-generated δ²H data to trace plant water sources and determine the water use strategies in plant and ecosystem studies.