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The roof of coal seams are mostly soft rock with weak cementation. To further study the mechanical characteristics and deformation control scheme of the roadway with weakly cemented siltstone as roof, this paper took Linchang coal mine as the research background and adopted field investigation methods, laboratory experiments, and theoretical analysis. Using a scanning electron microscope, it is found that the weakly cemented siltstone is composed of coarse-grained minerals with a high degree of pore development. According to the analysis, the instability factors of weakly cemented siltstone roadway include the late diagenetic age of rock, the low mechanical strength of rock, and the change of surrounding rock properties by pouring water. The selection of grouting reinforcement materials was studied in detail. The test results show that cement-bonded specimens’ strength is lower than that of Marithan polyurethane cement specimens in general. The combined support scheme based on grouting reinforcement is put forward. Field monitoring data show that the designed support scheme can effectively control the surrounding rock deformation of weakly cemented siltstone roadway.

Red-bed argillaceous siltstone is a common soft rock in the drawdown area of water diversion project extending from the Yangtze to Huaihe Rivers, with the characteristics of water softening and disintegration, which directly threatens the stability and safety of the diversion project. To better understand the effect of cyclic drying–wetting on the disintegration characteristics and mechanism, disintegration experiments were conducted on the red-bed argillaceous siltstone from the Tongcheng area of the water diversion project extending from the Yangtze to Huaihe Rivers. Experimental results indicated that, with an increasing number of drying–wetting cycles, the red-bed argillaceous siltstone was gradually crushed, large particles gradually transformed into small particles. A microstructural analysis showed that a continuous drying–wetting process resulted in the sample surface becoming disordered and complicated, and new micro-fractures and pores were generated. Notable changes in the concentrations of ions in the soaking solutions indicated continuous dissolution of the minerals, and a large amount of mineral loss under the action of cyclic drying–wetting. Furthermore, the evolution of disintegration parameter further indicated that the disintegration of red-bed argillaceous siltstone was gradually intensified by the increasing number of drying–wetting cycles. The fractal dimension D and the incremental surface energy gradually increased with an increase in the number of drying–wetting cycles. Thus, the proposed energy dissipation model effectively describes the disintegration characteristics of red-bed argillaceous siltstone under the cyclic drying–wetting, and thus, it can be used to guide engineering practices.

Weak rock slope instabilities are a common engineering problem during highway construction in South China. This study focused on a siltstone slope instability, which was induced during the construction of an expressway in Guangdong Province of China. Field monitoring and numerical simulation analyses were performed to examine the failure mechanism and formation processes of this landslide which is associated with construction activities and a period of prolonged rainfall. According to the characteristics of the slope deformation and the monitoring data, the slope deformation can be divided into two stages: a period of slow creep caused by excavation and an accelerated sliding period triggered by rainfall. Numerical simulation results show that during the excavation process, large horizontal displacement occurs at the front edge of the slope, and the initial plastic zone develops, resulting in a shallow landslide. During 20 days of continuous rainfall, the water content in the shallow layer of the slope increases continuously, and a transient saturated area forms at the surface of the slope. Within 7 days after the rain stops, the zero pore pressure surface of the slope gradually moves towards the interior of the slope, and the plastic zone begins to extend to the top of the slope. In addition, rainwater seeps down along the cracks to form a penetrating zone, thus accelerating the process of rock and soil mass softening, which further reduces the factor of safety of the slope. The combined effects of the excavation and rainfall ultimately lead to the failure of the siltstone slope; however, continuous rainfall is the key factor triggering deep sliding. The deformation and failure of the slope mainly undergo four stages: local collapse of the slope surface, formation of the plastic zone at the foot of the slope, bulging at the toe, and formation of tension cracks in the crown of the landslide. The failure mode of the siltstone slope belongs to be a retrogressive-type of the front edge bulging and trailing edge tension cracking. Based on the deformation characteristics and the failure mechanism of the landslide, comprehensive control measures including interim emergency mitigation measures and long-term mitigation measures are proposed.

The conceptual ability to source, combine, and store substances that enhance technology or social practices represents a benchmark in the evolution of complex human cognition. Excavations in 2008 at Blombos Cave, South Africa, revealed a processing workshop where a liquefied ochre-rich mixture was produced and stored in two Haliotis midae (abalone) shells 100,000 years ago. Ochre, bone, charcoal, grindstones, and hammerstones form a composite part of this production toolkit. The application of the mixture is unknown, but possibilities include decoration and skin protection.

The deformation in sedimentary rock induced by train loads has potential threat to the safe operation of tunnels. This study investigated the influence of stratification structure on the infrared radiation and temporal damage mechanism of hard siltstone. The uniaxial compression tests, coupled with acoustic emission (AE) and infrared radiation temperature (IRT) were conducted on siltstones with different stratification effects. The results revealed that the stratigraphic structure significantly affects the stress-strain response and strength degradation characteristics. The mechanical parameters exhibit anisotropy characteristics, and the stratification effect exhibits a negative correlation with the cracking stress and peak stress. The failure modes caused by the stratification effect show remarkable anisotropic features, including splitting failure (I: 0°–22.50°, II: 90°), composite failure (45°), and shearing failure (67.50°). The AE temporal sequences demonstrate a stepwise response characteristic to the loading stress level. The AE intensity indicates that the stress sensitivity of shearing failure and composite failure is generally greater than that of splitting failure. The IRT field has spatiotemporal migration and progressive dissimilation with stress loading and its dissimilation degree increases under higher stress levels. The stronger the stratification effect, the greater the dissimilation degree of the IRT field. The abnormal characteristic points of average infrared radiation temperature (AIRT) variance at local stress drop and peak stress can be used as early and late precursors to identify fracture instability. Theoretical analysis shows that the competitive relationship between compaction strengthening and fracturing damage intensifies the dissimilation of the infrared thermal field for an increasing stress level. The present study provides a theoretical reference for disaster warnings in hard sedimentary rock mass.

Research on Menanga Formation in Lampung and surrounding areas is still limited, especially research on paleontology. The purpose of this study was to identify the presence of radiolarian fossils in the Menanga Formation. Field observations were carried out at two site in Way Sabu, Pesawaran and Gunungkasih, Tanggamus, Lampung. Twelve samples were extracted from interbedded siltstone and claystone for radiolaria fossils. There were four samples that had radiolarian fossils. Radiolaria from genus Tetraditryma sp., Paronaella sp., Pantanellium sp., Holocryptocanium sp., Archaeocenosphaera sp., Napora sp., Sethocapsa sp., and Orbiculiforma sp. were found in the Menanga Formation indicate Jurassic to Cretaceous age. Based on radiolaria assemblage, Menanga Formation was probably positioned within a warm water current system in the low latitude Mesotethys. The exposed Menanga Formation caused by a collision between Woyla terrane and West Sumatra terrane that occurred in the Late Cretaceous.

Argillaceous siltstone is widely distributed along expressways in southern China; however, its strong water sensitivity and slaking properties severely restrict its utilization as subgrade fill, particularly under wet-dry cyclic conditions where bearing capacity deteriorates sharply. Existing studies have predominantly focused on mechanical performance evaluation of stabilizers, while systematic comparisons of lime and cement improvement effects and durability evolution under wet-dry cycles remain insufficiently understood. Drawing on the Yongjin Expressway reconstruction and expansion project, this study systematically investigates the durability of lime- and cement-improved argillaceous siltstone fill. Through unconfined compressive strength (UCS) tests, California bearing ratio (CBR) tests, and five wetting-drying cycles, the evolution differences in strength development, water stability, and durability between the two improvement schemes are revealed. Results indicate that, under identical stabilizer contents (3-7%) and curing conditions, the UCS and CBR of cement-improved soil are significantly higher than those of lime-improved soil. At the same dosage, the strength of cement-improved soil is approximately 1.5-1.7 times that of lime-improved soil, and the absolute strength gap further widens with increasing dosage. Both stabilizers effectively inhibit water immersion swelling, but the swelling rate of lime-improved soil is about 1.3-1.5 times that of cement-improved soil at the same dosage. At 7% dosage, the swelling rates of cement- and lime-improved soils decrease to 0.40% and 0.60%, respectively, both meeting subgrade fill swelling control requirements. After five wet-dry cycles, the UCS retention rate of 7% cement-improved soil is 78.3%, while that of lime-improved soil is 69.0%; the residual strengths are 507.0 kPa and 303.6 kPa, respectively, both satisfying general subgrade engineering strength requirements. However, the 3% lime-improved soil declines to 47.5 kPa after cycling, falling below the engineering threshold. Integrating strength, deformation, and durability indices, high-grade highway roadbeds and other high-load-bearing sections should prioritize 7% cement improvement, whereas general subgrade sections and locations emphasizing crack resistance may adopt 7% lime improvement as an alternative. Low-dosage (<5%) lime improvement is not recommended for argillaceous siltstone subgrade engineering. The findings provide a scientific basis for the engineering application of argillaceous siltstone as subgrade fill and for optimization of improvement schemes.

Sedimentary rock deposits such as siltstone have been attracting interest due to their potential to store and control the movement of sequestered CO2. An understanding of weak caprocks is required to guarantee the safety of CO2 geo-sequestration projects where weak rocks are encountered. The cost and challenge of obtaining intact samples of weak caprocks from depths relevant to potential geo-sequestration targets has resulted in relatively little data on their mechanical behaviour being available. This paper describes the manufacture and characterisation of artificial siltstones, with properties typical of weak rocks, at stress levels relevant to geo-sequestration. It is shown that the artificial siltstones with properties typical of weak rocks can be simply produced from mixtures of sand, feldspar fines, plaster and water.HighlightsWeak siltstones showed evidence of approaching critical states typical of de-structured granular materials when sheared to large deformations after yield.Drained triaxial tests revealed that the stress–strain response and failure mode depend on level of confining pressure and amount of cementation.The artificial siltstone can reproduce the strength, stiffness and mechanical behaviour of weak rock.

Conventional synchronous grouting materials often exhibit low early strength, delayed setting, and insufficient utilization of excavated soil, hindering the green and efficient advancement of metro shield tunneling technology. To overcome these challenges, this study developed a high-performance grouting material by utilizing shield muck—primarily composed of quartz (71.47%) and calcite (15.3%)—as the main raw material, with sodium trimethylsilanolate (TMS-Na) introduced as a performance enhancer. Through orthogonal experiments and range analysis, the influences of cement content, slag content, and TMS-Na dosage on the workability and mechanical properties of synchronous grouting materials were systematically evaluated. Microstructural evolution was characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric (TG) analysis, and mercury intrusion porosimetry (MIP) to elucidate the mechanism by which TMS-Na modifies the grout microstructure. The results demonstrate that incorporating 8% slag and 0.2% TMS-Na increases the utilization rate of shield muck to 60.8%. Compared with conventional grouts, the novel material exhibits approximately 97.4% and 93.3% enhancements in 3-day and 28-day compressive strength, respectively, alongside an impermeability grade reaching P10. The addition of slag improves the apparent density and early strength of the grout, although its contribution diminishes at later ages. TMS-Na effectively activates the hydration reactivity of slag, accelerates early hydration, reduces the setting time, and participates in a secondary hydration reaction with argillaceous siltstone present in the excavated soil, promoting the formation of additional calcium silicate hydrate (C-S-H). This process densifies the hardened grout matrix, refines the pore structure, and significantly enhances both mechanical performance and impermeability. Field application in a trial tunnel section confirms that the proposed grouting material achieves complete cavity filling, eliminates water leakage, controls ground deformation effectively, and offers favorable economic viability, demonstrating strong potential for large-scale engineering application.