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Rock joints in faulted zones are usually filled with large amounts of fault gouge, in which clay-rich fillings are very common. Fault water can significantly influence the mechanical parameters of clay-rich fillings and affect the shear mechanical behaviour of rock joints. Based on a tunnelling project passing through a faulted zone in Yunnan Province of China, this paper investigates the mechanical behaviour of rock joints with clay-rich fillings. A series of direct shear tests are conducted on rock joint samples made from rock blocks and fillings collected from a fault zone. The shear stress‒displacement curves and shear failure characteristics of rock joints are obtained, and several key factors of the fillings are considered, such as particle size, mineral composition, clay content, and water content. Furthermore, the peak and residual shear strengths are analysed by considering the influence of the water content and normal loading pressure. The test results show that water content of fillings has a great influence on shear strength of clay-filling rock joints; there is a trend to a negative correlation between the shear strength of rock joints when water content (w) exceeds the plastic limit (wp). Finally, a shear strength model for rock joints with clay-rich fillings is proposed based on the JRC-JCS strength criterion.Influence of water content on the shear strength of rock joints with clay-rich fillings is studied.A series of direct shear tests are conducted on rock joint samples based on a tunnelling project.The shear stress–displacement curves of rock joints with clay-rich filling are obtained.A shear strength weakening model of clay-filled joints is proposed.HighlightsInfluence of water content on the shear strength of rock joints with clay-rich fillings is studied.A series of direct shear tests are conducted on rock joint samples based on a tunnelling project.The shear stress-displacement curves of rock joints with clay-rich filling are obtained.A shear strength weakening model of clay-filled joints is proposed.

This study introduces a novel approach to power system fault diagnosis by synchronised phasor measurements. Conventionally, faults are diagnosed through the status of protective relays and circuit breakers which are activated following a fault. However, the hidden failures of the protection system has itself often been among the main suspects of partial or widespread blackouts. This study proposes an alternative fault diagnosis approach independent of the function of the protection system. An analytical method is introduced for power system fault diagnosis using dispersed synchronised measurements and bus impedance matrix (Zbus). Fault inception is first detected by local phasor measurement units (PMUs). Fault diagnosis is then carried out in a hierarchical manner so that first the faulted zone of the system is diagnosed, next the faulted line in the faulted zone is diagnosed and finally the fault point along the diagnosed line is located by gradient descent. The proposed method is applied to the WSCC 9-bus, where fault incidents on all of the transmission lines are examined. Moreover, the proposed method is successfully applied to the IEEE 118-bus test system consisting of 28 PMUs, which demonstrates successful fault diagnosis and location for a large-scale power system despite the limited coverage of PMUs.

During the construction of engineering projects, it is inevitable to cross fault and fractured zones, which are key geological factors that affect the stability of surrounding rock in tunnels. To study the distribution pattern of instability in surrounding rock and the optimization of synergetic support systems in fault-crossing tunnels, a comprehensive identification method integrating multi-source geological information was proposed, fully considering the geometric shape and distribution characteristics of rock fractures. The location of faults in actual projects was determined using this method, and a detailed three-dimensional numerical model was established accordingly. By simulating tunnel excavation, the spatial distribution pattern and grading characteristics of unstable blocks in surrounding rock were analyzed. Meanwhile, based on the original support methods, the effectiveness of synergetic support in stabilizing surrounding rock in tunnels was revealed, and initial support measures tailored to the characteristics of fault-crossing tunnels were proposed. The research results can provide reliable references for disaster prediction, prevention, and control in fault-crossing tunnels and underground engineering.

The paper offers a criterion to estimate geodynamic hazard of underground or surface stratified mineral mining based on the variation of energy stored due to mining.

Turbidite fans, serving as good reservoirs for petroleum accumulation, are typically formed during deep faulting periods in continental basins, particularly in steep slope zones. However, gentle slope zones are also significant and unique for the formation of turbidite fans. These turbidite fans hold immense importance in exploring concealed lithological reservoirs. Taking the Chezhen Depression of Bohai Bay Basin as an example, we conducted a comprehensive study of the turbidite fan deposits in the gentle slope zone. Our results indicate that (1) small-scale distal-source turbidite fans are a common sedimentary type in the Chezhen Depression of the Bohai Bay Basin; (2) the study area is mainly characterized by seven lithofacies; (3) there are incomplete Bouma sequences in the study interval. This study is an important turbidite investigation into continental faulted basins, and it can also provide an important reference value for exploration and development in unconventional reservoirs of the same type.

Fault zones have always drawn attention from the industry, and the performance of a quantitative interpretation of the fault interior structure on seismic data has remained as a big challenge. In this work, we focus on quantitatively populating the heterogeneity of the fault interior structure in a three-dimensional space on seismic data. To realize this goal, we take the South Wuerxun sub-depression in Hailar Basin as an example of a faulted basin. First, based on a heterogeneity analysis using the drilling and logging information from wells, we establish fault zone geologic models and perform seismic forward modeling to determine the relationship between different fault zone models with different fault dips, internal fillings, and P wave responses. Next, the fault interior structure index (FIS) is constructed, and the response features on the FIS from the fault facies and the host rock are observed. Finally, the FIS is applied to perform the quantitative interpretation and prediction of the heterogeneity in the FIS on seismic data. The results show that the FIS response from the fault zone is higher than that of the host rock in plane, indicating that the former is quantitatively separated from the surrounding host rocks. The FIS values greater than 26 represent the feedback from the fault facies, whereas those less than 26 represent the response from the host rocks. The FIS shows segmented features in the strike, banded in dip on plane. On the slip surface, the FIS indicates the shale smear zone and the location where low-graded and small-scaled faults are densely developed. The heterogeneity prediction result is proven by oil and gas exploration activities. The study results imply that the FIS could indicate a favorable path of the hydrocarbon migration in the fault zone and evaluate the fault sealing parts. The method can explore the quantitative characterization of fault facies and has essential popularization and application values in similar geological application fields, including hydrocarbon exploration, development of faulted reservoirs, and geological engineering evaluation related to faults.

Most given techniques tend to block the differential measurement during that portion of the cycle when a current transformer (CT) is saturated. Some other techniques bring more meaning to the breakpoint settings of the operating characteristic. The time and frequency localisation properties of continuous wavelet transform (WT) offer a viable and improved option for analysing the transient characteristics of defect signals. WT depends on high frequencies of the faulted signal produced due to CT saturation. The proposed technique is based on the windowed WT of fault-generated transients to distinguish between faults in a busbar protection zone from those outside the zone, particularly in case of an early and severe CT saturation. New differential busbar characteristic with values depending on the windowed WT of fault-generated transients has also been described.