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Seismic-induced secondary disasters, such as collapses and landslides, generate loose deposits in gullies. Under the influence of intense rainfalls, these deposits can become destabilized and lead to the initiation of large-scale debris flow. The systematic study of this type of debris flow and the revelation of its initiation mechanism and destruction law can provide certain theoretical references for the debris flow prevention and control project in the southwest region in China, where such events are particularly prevalent. Therefore, based on the current state of domestic and international research, this study focuses on analyzing the factors affecting the stability of gully deposits, categorizes four destabilisation types, distills the initiation mechanism of two types of gully deposits, and summarizes three types of critical initiation models for debris flow triggered by the destabilisation of gully deposits from the perspective of hydrologic debris flows. Finally, due to the complexity of the initiation process of debris flow triggered by the destabilisation of gully deposits, three critical scientific issues involved in this type of debris flow are proposed based on the analysis of the shortcomings of the existing results. [ABSTRACT FROM AUTHOR]

The discrete element method (DEM) was employed to investigate the initiation mechanism of an earthquake-triggered loess-mudstone landslide that occurred in 1920 in Gansu Province, China. The slope macroscopic damage phenomena, the microscopic crack evolution characteristics of the sliding zone, and the stress and velocity characteristics during the landslide initiation were analyzed. First, our findings show that the slope failure begins with tension damage at the upper slope, and the sliding zone is formed after the damaged crack group in the loess–mudstone interface propagates to the slope toe. Furthermore, the micro-crack revolution results reveal that the expansion rate of the sliding zone begins to decrease in the middle section of the slope. Combined with the rapid growth of the micro-crack after this section was damaged, the middle section of the slope is identified as the locked segment. During the failure of the locked segment, the stress of this section exhibits a sharp drop, suggesting a brittle damage form of the locked segment. In addition, velocity measurement results indicate that the sliding mass has an initial speed of about 4.75 m/s, which is rare in the low-angle loess-mudstone interface landslides. We conclude that the strain energy is converted into kinetic energy during the locked segment failure process, producing a start-up acceleration effect. Combined with seismic peak ground acceleration (PGA) analysis results, we proposed that the sequential effects of the seismic amplification, failure of the locked segment, and start-up acceleration caused the unique failure mode of the Sunjiagou landslide. [ABSTRACT FROM AUTHOR]

In this paper, a novel calculating method for the three-dimensional stress intensity factor (SIF) was put out. By using the finite element approach, it was possible to compute the Mode I, Mode II, and Mode III SIF under the impact of a single factor (height, width, thickness, crack length, and inclination angle) and derive its variation rule. The SIF was computed by using the uniform design method, which also yielded the fitting formula that could determine the fracture at any geometric position on any plate. Then, a new three-dimensional penetrating crack fracture criterion was established to forecast both Mode I, Mode II, and Mode III initiation parameters of three-dimensional penetrating oblique crack. Uniaxial compression tests were done in order to validate the forecasted outcomes, including the crack initiation angle and load. The results demonstrate that the normalized KI always decreases with z/t (the crack front spacing), while the normalized KII and KIII increase first and then decrease. KI and KIII increase with the crack length 2a, while KII decreases first and then increases with the crack length. KI and KII both increase with the plate height. KI rises with the crack inclination angle, while KII and KIII initially raise and then lower. Along with the crack inclination angle, the crack initiation angle decreases, and the crack initiation stress rises. All of fracture mechanisms are Mode I. [ABSTRACT FROM AUTHOR]

West China experienced an extremely wet autumn in 2017, and the amount of September–October precipitation is the greatest during 1961–2018. This study explored the physical processes responsible for two primary intraseasonal precipitation events which contribute greatly to such an extremely wet season. The first event peaking in early September is induced by the southward movement of a frontal system from the northern China, which is attributed to the southward displacement of an intraseasonal anticyclonic anomaly. The northerly anomaly associated with the anticyclone advects cold air into West China and thus triggers frontal precipitation. The second event peaking in early October is related to the northward shift and intensification of an intraseasonal anticyclonic anomaly centred over the northwestern Pacific Ocean. The southerly anomaly along the western flank of the anticyclone transports moisture to West China and thus triggers precipitation. The different initiation processes for the two precipitation events may be due to the distinct dynamical and thermal‐dynamical conditions in September and October. West China has sufficient moisture but less dynamical disturbances in September, while it has adequate dynamical disturbances but less moisture in October. [ABSTRACT FROM AUTHOR]

Hydrodynamic-driven bedding rock landslides are the focus of research in the field of landslide geological hazards due to their large number, frequent disasters, and excessive harm. However, the understanding of the initiation mechanism of landslides is still insufficient, and the accurate prediction of landslides still faces great challenges. Because of this, this paper takes moderate-dip angle bedding rock landslides with weak interlayers as the research object and conducts a series of landslide model tests under the action of hydrodynamics by constructing an ideal single-layer landslide physical model. On this basis, the macroscopic deformation evolution process of the landslide and the erosion degradation characteristics of the slide zone soil is analyzed in depth. The results show that the failure of bedding rock landslides is associated with the slip surface roughness and dip angle and can go through four stages: the initial deformation stage, uniform deformation stage, accelerated deformation stage, and failure stage.The seepage erosion in the sliding zone causes the loss of aggregates, which reduces the shear strength and causes the slope to slide. Simultaneously, the compression-shear action and the deformation of the overlying slope also adversely affect erosion strength.Based on the variation law of soil cohesion in the sliding zone with hydraulic gradient and erosion time, a seepage-driven evolution model of soil cohesion in the sliding zone is proposed, which can describe the degradation process of soil cohesion in the sliding zone well. The existence of sliding surface roughness not only significantly affects the deterioration law of the sliding zone, but also changes the failure modes of different regions of the sliding zone. By considering the influence of the roughness on the failure modes of different areas of the sliding zone, the multi-effect correlation analysis of dynamic water is carried out, and the mechanical model of the landslide is established, which realizes the effective evaluation of the dynamic stability of the landslide. The research achievements in this study can provide a theoretical reference for predicting and preventing actual hydrodynamic-driven bedding rock landslides.

The occurrence of loess landslides is particularly closely related to rainfall. In order to deeply understand the promotional effect of rainfall infiltration on landslides, based on the investigation of “9?17” Baqiao landslide in Xi'an area of Shaanxi, the numerical simulation methods were used to systematically study the change response characteristics and spatial- temporal distribution laws of the relevant physical and mechanical parameters of the loess slope under the rainfall infiltration conditions, analyze the destabilization process of the slope from the perspective of the change of the safety factor of sliding surface, and reveal the initiation mechanism of this type of landslide. The results show that ① the action of rainfall causes a gradual decrease in the matrix suction of the slope soil, and the magnitude of the decrease varies at different distribution locations; ② before the initiation of the landslide, the range of high volume moisture of the slope body expands significantly with rainfall, and the volume moisture shows the law of decreasing from paleosoil layer to the adjacent loess layer; ③ the horizontal displacement of the slope is radially decreasing from the middle to the upper and lower parts of the slope body, while the vertical displacement gradually decreases from the top to the bottom, and the safety coefficient of its critical sliding surface gradually decreases with the process of rainfall infiltration; ④ the response time and magnitude of pore water pressure and the change of volume moisture in the soil at the nodal development site are earlier and stronger than those in other areas of the slope, and the regional distribution of the maximum shear strain within the slope is basically parallel to the slope surface, and the simulation results are consistent with the prototype landslide; ⑤ based on the unique water-sensitive nature of loess, and the influence of causal factors such as geological structure or human engineering activities, the existence of loess joints and fissures provides an advantageous channel for water infiltration and transport, and rainfall accelerates the process of loess subduction and slope structure destruction, changing the internal stress field, displacement field and hydrogeological conditions of the slope, which in turn promotes the occurrence of landslides. [ABSTRACT FROM AUTHOR]

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Based on the distributed dislocation function, the complex function of arbitrary position and branch cross-crack group under hydraulic-mechanical in the infinite plate is derived and the maximum Mode I and Mode II stress intensity factors (SIFs) of cross-crack group are obtained. The influence of cross-crack group geometry parameters on the maximum SIFs is analyzed and the multiple cross-cracks dangerous zone is obtained. Using the maximum shear and tensile SIF ratio criterion as a basis, the initiation process of double cross-cracks is predicted and verified by red sandstone double cross-cracks uniaxial compression test. Results show that for the double cross-crack in an infinite plate, h/a should be greater than 8 and the value of α 2 should not range from 75° to 90° to avoid possible cracking. For the triple cross-crack in an infinite plate, when the water pressure is low (less than 5 MPa), the influence of the stress field exceeds the influence of water pressure. For red sandstone samples with double cross-cracks under uniaxial compression, the inner tips of cross-cracks always connected and penetrated and the inner and outer tips of cross-cracks often eventually joined together. The multiple cross-crack initiation criterion was validated by the good agreement between the test results and the prediction results of red sandstone with double cross-cracks. All the initiation mechanisms are Mode I fracture. [ABSTRACT FROM AUTHOR]

Freeze-thaw cycles are recognized as one of the key triggers for some major landslides in cold regions around the world. Though the effects of freeze-thaw cycles on the rock strength degradation have been studied extensively, little effort has been made to qualitatively evaluate how it contributes to the evolution from a stable rock slope to a large-scale mass movement. In this study, we use a discrete element-based numerical model to simulate the entire process of the initiation of landslide under the action of freeze-thaw cycles in a slope with randomly distributed initial cracks. The main goal of this work is to quantitatively describe the landslide evolution process regarding the slope displacement, crack propagation, stress chain and load-bearing structure. Our results show the essence of the displacement evolution of a landslide subjected to freeze-thaw cycles; namely frost heave pressure induces the generation of new cracks, leading to the failure and reconstruction of the load-bearing structure of the slope. Deep-seated landslides can occur when the slope is crossed by a fault; otherwise, the slope is prone to surface erosion or shallow landslides. [ABSTRACT FROM AUTHOR]

Debris flow is a common mountain disaster with complex formation process and strong destructive power in China. And debris flow causes serious economic losses and casualties. The research on the initiation mechanism of debris flow is the core issue of the study of debris flow catastrophic mechanism. And the research on the starting mechanism of debris flow is the basis for the research and development of the theory and technology for disaster prevention and mitigation of debris flow. In this paper, the existing research results of the initiating mechanism of soil-mechanical debris flow and the disaster-pregnancy conditions of debris flow initiating were systematically sorted out and summarized. The study of initiating mechanism of soil-mechanical debris flow and its advantages and disadvantages by scholars at home and abroad were analyzed and discussed. The starting model of the current soil-mechanical debris flow was presented. Finally, the insufficiency of the current research on the starting mechanism of the soil-mechanical debris flow and the future development direction were analyzed and discussed. This research has certain value for the study of the initiation mechanism of soil-mechanical debris flow and the development of discipline. [ABSTRACT FROM AUTHOR]

The structure of loess is loose, and the shear strength of loess drops sharply after contact with water. Therefore, loess mudflows have become a common geological disaster on the Chinese Loess Plateau. In order to study the initiation mode and mechanism of loess mudflows, in this study, seven sets of flume experiments were designed by controlling the slope angle and rainfall intensity. The results show that (1) when the slope angle is between 10° and 20°, there are two initiation mechanisms of loess mudflows: mudflow (large scale) and retrogressive toe sliding, and mudflow (small-scale) and retrogressive toe sliding. (2) The main method by which water infiltrates into the soil accumulation is mainly vertical infiltration, which is not affected by the slope angle and the seepage direction of the accumulation soil. (3) The liquefaction of loess is the root cause of loess mudflows. Water infiltrates into the area with an uneven density and a large amount of water accumulates in this area. Thus, the water content of the loess increases and the pore water pressure increases quickly and cannot dissipate in time, so the loess liquefies and the liquefacted area continues to spread and become larger. Thus, loess mudflows (large scale) occur. The increase in pore water pressure was captured in the seven sets of experiments. However, the order of the rising positions in the accumulation were different. This requires us to carry out tracking of the particle displacement inside the soil and the spatial changes in the internal structure of the soil in future research. [ABSTRACT FROM AUTHOR]

The Jiangjia Gully, which is located in Dongchuan District, Yunnan Province, China, is a watershed prone to debris flows and has long-term recorded data of debris-flow occurrence. However, the initiation mechanism has mainly been studied by experiments in this watershed. To further reveal debris-flow formation mechanism in the Jiangjia Gully, debris-flow activities in the initiation zone were observed with hand-held video cameras in the summer of 2016 and 2017. In these two years, six debris-flow events were triggered in Menqian Gully, a major tributary of the Jiangjia Gully, while debris-flow activities in some sub-watersheds of Menqian Gully were recorded with video cameras in four events. The video recording shows that landslides constituted an important source for sediment supply in debris flow. Some landslides directly evolved into debris flows, while the others released sediment into rills and channels, where debris flows were generated for sediment entrainment by water flow. Therefore, debris-flow occurrence in the Jiangjia Gully is influenced both by infiltration-dominated processes and by runoff-dominated processes. In addition, rainfall data from four gauges installed in Menqian Gully were analyzed using mean intensity (I), duration (D), peak 10-minute rainfall (R10min) and antecedent rainfall (AR) up to 15 days prior to peak 10-minute rainfall. It reveals that debris-flow triggering events can be discriminated from non-triggering events either by an I-D threshold or by an R10min-AR threshold. However, false alarms can be greatly reduced if these two kinds of thresholds are used together. Moreover, behaviors including intermittency of debris flow, variance in moisture content and volume among surges, and coalescence of multiple surges by temporary damming were observed, indicating the complexity of debris-flow initiation processes. These findings are expected to enhance our knowledge on debris-flow formation mechanism in regions with similar environmental settings. [ABSTRACT FROM AUTHOR]

Enhanced debris flow activity observed after the 2008 Wenchuan earthquake, Sichuan Province, SW China, is still intense more than a decade since the earthquake. A heavy rainstorm on 20 August 2019 caused catastrophic debris flows in the epicentral area of the earthquake. By remote sensing imagery interpretation and field investigation, 13 debris flows were identified. An empirical rainfall threshold I-D model (intensity–duration) of post-seismic debris flows is established. Changing rainfall thresholds, characteristics, and initiation mechanisms of the 2019 debris flows were analyzed, which are different from the events that occurred in previous years. We find that the 2019 debris flows were mainly initiated by concentrated runoff erosion of sediments stored in tributary channels of catchments, with little contribution from the coseismic landslides and new hillslope failures. Differently, the major sediment supply of debris flows in previous years was mainly from the reactivation of coseismic landslide deposits. By analyzing the triggering rainfall of all recorded debris flows after the Wenchuan earthquake, we find that the rainfall threshold in 2019 is about 1/2–4/5 of the pre-earthquake value, and the I-D model we built can predict the 2019 debris flows successfully. Considering that there are still a large number of coseismic landslide deposits in the mountain catchments and the rainfall thresholds are slowly recovering, the post-seismic debris flows may last for a long period. [ABSTRACT FROM AUTHOR]

Different engineering structures, e.g., long-span bridges, bundled conductors, and cable-supported photovoltaic modules, exhibit various frequency relationships among different degrees of freedom (DOFs). Despite extensive research, the initiation mechanisms of flutter remain somewhat ambiguous for a 3-DOF system considering heaving-lateral-torsional motions, especially when frequencies are close among different DOFs. This study introduced an explicit eigenvalue solution framework for tackling the 3-DOF linear flutter problem by utilizing matrix perturbation methods, enabling the extraction of modal damping and frequency solutions for all possible frequency scenarios. These solutions explicitly clarified the influence mechanism of all flutter derivatives (aerodynamic damping and stiffness), structural frequencies, and mechanical dampings. Important flutter derivatives, flutter risk level, and sensitivity level to mechanical damping and to frequency detuning were summarized in a table for all frequency scenarios, providing a panoramic perspective on flutter instability and the coupling mechanism. Numerical studies were conducted on a thin plate, the Akashi Kaikyo Bridge, and an eight-bundled conductor to examine the proposed explicit solutions. The results showed that approaching frequencies can amplify the coupling effect among different DOFs by half an order, but this does not necessarily mean the system is more prone to flutter. A system where the torsional frequency approximates the heaving/lateral frequency is expected to face a higher flutter risk if given significant torsional-related aerodynamic stiffness (H 3 * , P 3 *). Evidently, this high risk exhibits insensitivity to mechanical damping and small frequency-detuning. Though usually ignored in bridge flutter analysis, drag force and lateral motion could exert noticeable influence in a minority of cases, e.g., more than 10 m/s decrease of critical wind speed for the Akashi Kaikyo Bridge at large angles of attack. The proposed explicit solution framework provides a systematic view and new insights into the flutter initiation mechanism, serving as a reference in the design and studies of various engineering structures with different frequencies and coupling features. • Explicit solutions for modal damping and frequency are provided for 3-DOF linear flutter. • For all frequency scenarios, flutter initiation mechanism and coupling effect are revealed and compared. • Influence mechanism of all flutter derivatives and structural parameters are clarified. • Flutter risk and sensitivity level are summarized, providing design guidance for various structures. • Drag force and lateral motion could be important for bridge flutter at large attack angles. [ABSTRACT FROM AUTHOR]

On May 12, 2019, a landslide occurred near a construction site of a reservoir dam along the left bank of the Wulong River, Qinghai Province, China. Video footage showed that the entire failure process of the landslide lasted for 15 min. Although an excavator that parked on the foundation pit was buried and the Wulong River was blocked, this landslide did not cause any casualties. Based on field investigations, 3D laser scanning, unmanned aerial vehicle observations, and borehole surveys, this study aims to reveal the cause and initiation mechanisms of the landslide. The landslide developed on a typical dip slope with thick-bedded conglomerates intercalated with a few mudstone layers. The slide mass mainly consisted of conglomerates with a dip angle varying from 20 to 40°, failing along bedding plane contacts with the underlying muddy intercalation. Numerous tension cracks had developed in the upper part of the slope due to stress relaxation during the process of bank slope evolution associated with rapid river incision. These cracks damaged the integrity of the rock mass and promoted rapid rainfall infiltration. The water infiltrated into the slope and deteriorated the mechanical properties of the rock mass, which resulted in long-term deterioration of the slope stability conditions. In addition, the temperature of Tongren County was below zero for 5 months in a year, hence the freeze–thaw cycle of the water filled in the cracks would have reduced the shear strength further. There were 10 days of continuous rainfall before the landslide occurred, and the cumulative precipitation in 2018 and 2019 was also significantly more than that of previous years. Three primary factors are involved in the landslide event: (1) thick-bedded conglomerates intercalated with a few mudstone layers with contrasts in strength, (2) development of numerous relaxation cracks, and (3) long-term rainfall accumulation. [ABSTRACT FROM AUTHOR]

This paper provides newly found and profound insight into the initiation mechanism of the first Baige landslide occurred on the upper reaches of the Jinsha River in October 10, 2018. The detailed geological characteristics are interpreted by comprehensive field surveys in the past year, which indicate that the Baige landslide developed in the Jinsha River tectonic suture zone, and the active tectogenesis significantly contributes to broken stratigraphic structures and complex spatial distribution of lithologies. The initiation is considered to be long-term creep under the exogenic and endogenic integration, while the active tectogenesis and the influence of serpentinite and foliation, respectively, are the primary exogenic and endogenic factors. In addition, this creep process can be analyzed within three stages: evolution and formation of failure-prone geological structures, progressive deformation and fracturing, and shear failure of the locking section. The distribution and easily degraded behavior of the serpentinite are the fundamental, enabling the formation of failure-prone structures and also responsible for the subsequent deformation evolution. The foliation controls the toppling deformation-failure mode and direction. Furthermore, this catastrophic landslide further reminds us to pay attention to the landslides along the upper reaches of the Jinsha River, and our preliminary results indicate that the distribution characteristics of landslides significantly depend on the Jinsha River tectonic suture zone and the serpentinite mélange belt and thus are always associated with tectonically induced damage. [ABSTRACT FROM AUTHOR]

The Oblique Detonation Wave Engine is expected to propel the aircraft to hypersonic speeds. Currently available studies are mainly focused on the initiation characteristics of the oblique detonation wave on a straight wedge. The control method is of great importance for a better thrust performance. However, there lacks the trigger location control method of the oblique detonation wave. In the current research, a co-flow hot jet is utilized to initiate the oblique detonation wave with an initiation length shorter than that on a straight wedge. The performance of the co-flow hot jet under different inflow pressures is discussed in detail. The mechanism for the initiation of the oblique detonation wave by the co-flow hot jet is revealed. It is found that the key for the initiation by the co-flow hot jet is an underexpanded jet, which is featured by a first jet shock wave, a second jet shock wave, an expansion fan, and an intercepting shock wave. The first and second jet shock waves are observed for the first time in the research of the oblique detonation wave. The strength of the first and second jet shock waves is higher than that of the leading shock wave, reducing the initiation length of the oblique detonation wave greatly. This investigation reveals the initiation mechanism of the oblique detonation wave by the co-flow hot jet, which is of great importance for its application in the Oblique Detonation Wave Engine. • A co-flow hot jet is utilized to initiate the oblique detonation wave. • The key to the initiation by the co-flow hot jet is an underexpanded jet. • The performance of the co-flow hot jet under different inflow pressures is discussed in detail. [ABSTRACT FROM AUTHOR]

A rockslide of 5.0-million-m3 volume occurred on June 5, 2009, in Jiweishan, Chongqing, China. The field investigation indicates that the kinetic process of the Jiweishan rockslide was divided into four stages: the initiation of ejection, flying and scraping, colliding and direction altering, and stopping and accumulating. The rock mass had been considered stable according to the principle of statics. To investigate the possible initiation mechanism, the present research proposes a new initiation model that considers the vibration effects as a shaking force (F), which acts against the rockslide mass in the direction normal to the rupture surface at the same instant when the brittle limestone is ruptured. The amplitude of F was best estimated as τ · A F , where τ and AF are the shear stress and area of the rupture surface, respectively; under this model, the initial ejection direction agrees very well with the observed direction. The movement characteristics of the slide were later identified by assuming a variety of friction angles (at 0°, 5°, 10°, and 15°) at the weak slip surface. It is observed that when the friction angle ranged from 0° to 5°, the velocity of the rockslide reached 68.3–79.2 m/s and the rockslide mass could fly to the observed scraping area. Furthermore, the velocity and duration at each moving stage were estimated, using the assumptions in the shaking force and friction angle. Results show that the total travel time of Jiweishan rockslide was 66.8–78.6 s, which is close to 60 s as estimated by eyewitnesses and the seismic wave records. [ABSTRACT FROM AUTHOR]

For the first time, a quantum-chemical study of the initiation mechanism of the cationic polymerisation monomer p-methylstyrene in the presence of a complex catalyst of aluminum chloride -- hydrochloric acid in toluene with a stoichiometric composition of 1:1:4 by the ab initio method was performed. We showed that the energy barrier is 15 kJ/mol, and the thermal effect of the reaction is 113 kJ/mol. The reaction is of exotermic character and represents the usual acceptance of a proton from the complex catalyst AlCl3-HCl and its attachment to the most hydrogenated carbon atom C(1). [ABSTRACT FROM AUTHOR]

On 2 September 2018, an intense rainstorm swept Mengdong Town in Yunnan Province of China, inducing a serious landslide and debris flow disaster with 10 deaths and 11 missing. Image interpretation, field survey, and slope stability analysis were used to examine the characteristics and initiation mechanism of this hazard. A total of 1774 landslide scars were identified, the area of which occupied 8.26% of the study region. Due to the spatial inhomogeneity of precipitation, these scars mainly concentrated along valleys in the lower part of the study area. Besides, well-forested hillslopes were more prone to landslides, indicating the limited role of trees in stabilizing slopes in extreme rainfall events. The initiation of landslides is mainly attributed to the week cohesion of the saturated clayey sand beneath the root zone, where the tensile resistance of roots was absent, and the increase of positive pore water pressure. Additionally, 288 landslide scars were situated adjacent to roads, demonstrating that the road construction activity had intensified the landslide disaster. Owing to the relatively low mobility of landslides, a considerable portion of landslide debris deposited on the valley floor in smaller watersheds (< 6.03 hm2), while the remaining portion entered high-order channels. In these channels, where stream power was relatively large, the woody debris and soil carried by landslides were entrained by streamflow, and debris flows were formed. Moreover, the magnitude of debris flow was amplified by the vertical and lateral erosion of the stream channel. [ABSTRACT FROM AUTHOR]

The first quantum-chemical study of the initiation mechanism of propylene in the presence of a complex chloride aluminium catalyst by the ab initio HF/6-311G** method was carried out with optimisation of the geometry in all parameters by a standard gradient method for attacks of the initiating particle on a-carbon monomer atoms. We showed that this reaction is barrier-like and exothermic. The mechanism of initiation is a coordinated process of SN 2-nucleophilic substitution. The energy barrier in the attack of the initiating particle on the a-carbon atom of propylene is 124 kJ/mol, the thermal effect of the reaction equals -49 kJ/mol. [ABSTRACT FROM AUTHOR]

The 2008 Wenchuan Ms8.0 earthquake triggered a catastrophic landslide, i.e., the Daguangbao (DGB) landslide (1.2 ✕ 109 m3). Its shear failure occurred within a deep-seated (average depth of 400 m) saturated carbonate bedding fault in the Paleozoic Formation. The frequent seismic events in the tectonic belt make the landslide initiation mechanism more complex. Shake table tests were conducted on the DGB landslide to understand the coupling effect of multiple earthquakes, geology and hydrology. The results showed that the multiple earthquakes weakened the friction coefficient as the Boltzmann function on the sliding surface of the landslide. The friction law of the basal surface related to seismic energy was established and incorporated into the Newmark analysis. And the seismic energy consumed in the steep scarp surface release of landslide during an earthquake is also considered. It found that the traditional Newmark model overestimates the time for earthquake-induced landslides due to ignoring the steep scarp surface release stage. It proposed that evaluating pre-earthquake induced slope damage, and critical seismic energy for triggering co-seismic landslides are important for predicting post-seismic landslides. [ABSTRACT FROM AUTHOR]

Drop-weight tests were conducted to investigate the impact-initiation sensitivity of high-temperature PTFE-Al-W reactive materials. The test results show that the impact-initiation sensitivity of the materials more than doubles with increasing the sample temperature from 25 to 350 °C. Combined with the impact-induced initiation process recorded by high-speed video and the difference between reacted and unreacted residues, the crack-induced initiation mechanism was revealed. The rapid propagation of crack provides a high-temperature and aerobic environment where Al reacts violently to PTFE, which induces the initiation. Moreover, the influence of sample temperature on the sensitivity was discussed and analyzed. The analysis results indicate that the sensitivity shows a temperature interval effect, and 127 and 327 °C are the interval boundaries where the sensitivity changes significantly. The sensitivity may leaps at 127 °C and increases more rapidly in the temperature interval from 127 to 327 °C, but hardly changes after the temperature reaches 327 °C.

The first quantum-chemical study of the initiation mechanism of isobutylene in the presence of a complex chloride aluminium catalyst by the ab initio HF/6-311G** method was carried out with optimisation of the geometry in all parameters by a standard gradient method for attacks of the initiating particle on α-carbon monomer atoms. We showed that this reaction is barrier-like and exothermic. The mechanism of initiation is a coordinated process of SN²-nucleophilic substitution. The energy barrier in the attack of the initiating particle on the α-carbon atom of isobutylene is 97 kJ/mol, the thermal effect of the reaction equals 44 kJ/mol. [ABSTRACT FROM AUTHOR]

Continuous use of diversion-based irrigation has been associated with an increase in the frequency of loess landslides on the South Jingyang Platform, Shaanxi, China. A loess landslide event with a maximum sliding distance of 278 m occurred near the village of Miaodian on May 26, 2015. This landslide event was characterized by four individual landslides. Field investigations, geological exploration, numerical simulation, isotropically consolidated undrained (ICU) triaxial tests, and ring shear tests were conducted to identify its initiation and movement mechanisms. The ICU tests revealed that saturated loess samples were highly liquefiable. High pore water pressure was quickly produced and deviation stress increased the highest value even at low values of axial strain. Geological investigations revealed that cracks penetrated into the saturated zone from the ground surface, and simulation results revealed that these cracks played a dominant role in the infiltration of surface water and led to a rise in the groundwater table. When the infiltration recharge exceeds the holding capacity of the paleosol, the latter behaves as aquifuge under relatively undrained conditions. This process results in the accumulation of water at the bottom of the loess layer, thereby contributing to soil liquefaction and landslide initiation. The ring shear tests revealed that the saturated sand layer of the landslide substrates was subjected to easily inducible high pore water pressure under undrained conditions which led to the thrusting of the sand layer onto the deposit surface and explains the high speed and long runout distance of this landslide. [ABSTRACT FROM AUTHOR]

The characteristics of debris flows (e.g., velocity, discharge, kinematic energy) are highly dependent on surges incurring abrupt changes to flow height, velocity, and boulder concentration. Therefore, understanding the initiation and runout characteristics of surges is essential when planning debris flow mitigation. Monitoring performed using 10 time-lapse cameras (TLCs) in Ohya landslide, central Japan, where debris flows occur frequently due to mobilization of storage (i.e., talus cone and channel deposits), allowed us to obtain data on a series of surge processes, from initiation to termination, which occurred during each debris flow event. We also analyzed temporal changes in the spatial distribution of storage in the debris flow initiation zone, associated with sediment supply from hillslopes and evacuation of sediment by the occurrence of debris flows, through periodic measurements of topography using unmanned aerial vehicles (UAVs). Debris flow surges were mainly induced by repetitive mass movement of storage through the erosion of channel deposits by overland flow, sliding of channel deposits, and sediment and water supply from channel banks and tributaries. Development of a spontaneous wave on the flow surface was not an important formation process of surges in the Ohya landslide. Many debris flow surges initiated at channel sections with deep storage (>2 m in depth), located <30 m below a junction with a tributary, when the maximum 10-min rainfall intensity exceeded 5 mm. Partly saturated flow, which has an unsaturated layer in its upper part, was the predominant flow type in the steep initiation zone, while fully saturated flow was predominant in the gentle transportation and deposition zones. Flow type often changed as the surges descended. Partly saturated flow was predominant when the volume of storage in the initiation zone was large, whereas fully saturated flow was predominant when the volume of storage was small. When we compared debris flows with similar total sediment volume, travel distance was long when fully saturated flow with high flow mobility was predominant because of the small volume of storage in the initiation zone. The volume of storage also affected flow path avulsion on the debris flow fan by controlling the flow mobility of surges. Consequently, the spatial distribution and total volume of storage are important factors controlling the initiation location, predominant flow type, and termination location of surges. • Initiation and runout of debris flow surges were observed in Ohya landslide, Japan. • Debris flow surges were mainly formed by repetitive mass movement of sediment storage. • Many surges occurred in channel sections with deep storage near channel junctions. • Partly saturated flow is the predominant flow type in the steep initiation zones. • Volume of storage in the initiation zone likely affected flow type of surges. [ABSTRACT FROM AUTHOR]

Titanium alloy fatigue limit is reduced by brittle coatings. • Tension-tension fatigue tests of TC4 alloy with brittle coatings were conducted. • Fatigue crack initiated in brittle coatings and propagated to the interface. • The fatigue limit stress is significantly reduced due to the brittle coatings. • The model of coating cracking-induced fatigue decrease is proposed. In order to study the coating effects on fatigue crack initiation mechanism in Ti-alloys, two types of brittle coatings, CrAlN and TiN, were deposited on the surface of TC4 titanium alloy by physical vapor deposition. The tension-tension fatigue tests and the in-situ observations of fatigue crack morphology were performed to study the coating effects on the fatigue crack initiation and propagation in the Ti-6Al-4V alloy. It was found that the 510–530 MPa TC4 fatigue limit is reduced to 315–330 MPa due to the CrAlN coating. The brittle coatings impeded the deformation of the TC4 samples at the beginning stage of fatigue tests, while coating cracking promoted the elongation of the tested samples. Fatigue crack was found to be initiated in the brittle coatings and propagated to the coating-substrate interface, inducing micro-damage of the substrate surface. The fracture surface of coated and uncoated samples was quite different, and the formation of non-propagating fatigue cracks was also observed. The coating cracking-induced low cyclic stress substrate damage model was proposed. This study should be of significance for the coating improvement and provides a theoretical basis for improving fatigue properties of coating materials. [ABSTRACT FROM AUTHOR]

Particle size distribution of the gravelly soil in debris flow source area has a great impact on the formation mechanism of debris-flow. In order to explore the relationship between particle composition and debris flow initiation, we collected 182 soil samples from debris flow source areas. Sieving tests have been conducted in the laboratory to acquire the fundamental particle size distribution data. Subsequently, the fractal theory was employed to compute the fractal dimension of each soil sample, analyzing the results of calculation we found that the gravelly soil in debris flow source area is mainly concentrated in one fractal dimension, the value of which ranges from about 2.250 to 2.798. Comparing the results of calculation and sieving experimentation, the underlying relationship between particle composition and fractal dimension can be revealed: the particle compositions of the gravelly soil tend to remain uniform as the fractal dimension increases. On the basis of the calculation results, the in-situ artificial rainfall experiments can be designed and performed. Analyzing the phenomenon during the processes of the experiments, the initiation mechanism with different fractal dimensions can be preliminarily identified: The gravelly soil which can mobilise into debris flows exhibits significant criticality feature, and the gravelly soil with fractal dimension ranges from 2.4 to 2.6 are more susceptible to mobilise into debris flow, and the scale of the debris flow is relatively larger. For slopes with fractal dimension < 2.4, the possibility of mobilisation into debris flow is extremely low. When fractal dimension ranges from about 2.6 to 2.7, the density of the formed debris flow is relatively lower, under which the formation of debris flows exhibits significant intermittent characteristics. [ABSTRACT FROM AUTHOR]

The first quantum-chemical study of the initiation mechanism of 4-methylpentene-1 in the presence of a complex chloride aluminium catalyst by the ab initio HF/6-311G** method was carried out with optimisation of the geometry in all parameters by a standard gradient method for attacks of the initiating particle on α-carbon monomer atoms. We showed that these reactions are barrier-like and exothermic. The mechanism of initiation is a coordinated process of SN 2-nucleophilic substitution. The energy barrier in the attack of the initiating particle on the α-carbon atom of 4-methylpentene-1 is 94 kJ/mol, the thermal effect of the reaction equals 52 kJ/mol. [ABSTRACT FROM AUTHOR]

The first quantum-chemical study of the initiation mechanism of p-isopropylstyrene in the presence of a complex boron fluoride catalyst by the classical ab initio method in the 6-311G** basis was carried out with optimisation of the geometry in all parameters by a standard gradient method for attacks of the initiating particle on α-carbon monomer atoms. It is shown that these reactions are barrier-like and exothermic. The mechanism of initiation is a coordinated process of SN²-nucleophilic substitution. The energy barrier in the attack of the initiating particle on the α-carbon atom of p-methylstyrene is197 kJ/mol, the thermal effect of the reaction equals 31 kJ/mol. [ABSTRACT FROM AUTHOR]

Unsaturated polyester resins (UPR) cured with styrene has been widely used in the various industrial fields. Methyl ethyl ketone peroxides (MEKP)-cobalt(II) system is the most common initiator for the curing of UPR. However, its initiation mechanisms currently remain elusive. In this study, the monomeric MEKP (MEKP-1) was firstly separated out from the commercial MEKP products, and then the radical initiation mechanisms of MEKP-1 catalyzed by cobalt isooctoate in the presence and absence of styrene were comparatively investigated by a combination of nitroxide radical trapping technique and HPLC-ESI/MS (high performance liquid chromatography-electrospray ionization/mass spectrometry). The amount of trapped products originated from methyl radical, ethyl radical and hydroxyl radical was significantly larger than that of trapped products from other radicals. These results indicated that methyl, ethyl and hydroxyl radicals were the dominant intermediate radicals formed in the initiation process of MEKP-cobalt(II) system, which would serve as the primary source to initiate styrene polymerization. [ABSTRACT FROM AUTHOR]

In this study we analyse the spatial distribution of potential lahar sources during long-lasting eruptions using two slope stability models (SHALSTAB and TRIGRS). The analysis is based on observed deposit grain-size and thickness, rainfall data and slope angle of the lahar events, in the area surrounding the Cordón Caulle volcano, Chile, that occurred during the 2011 eruption. The main phase of the eruption (4–7 June) was characterized by eruptive plumes from 7 to 11 km high which dispersed most of the tephra eastward toward Argentina, with a total estimated volume of about 1 km 3 . Tephra-fallout blanketed the region from ESE to ENE of the volcano with the thickness of the tephra-fallout layers between approximately 1 m (15 km from vent) and 0.06 m (240 km from the vent). On 10 June 2011, a major lahar occurred close to the Argentina-Chile border that reached the National road 231 (28 km from the vent). Three field campaigns were undertaken to collect samples and data from tephra-fallout deposits and triggering mechanisms in the lahar source area. Model input parameters were obtained from geotechnical tests and field measurements. Several metrics were used for model evaluation and best fit to the data were obtained for simulations considering non-cohesive ash layers for SHALSTAB and a cohesion of 0.5 kPa for TRIGRS. Both models are sensitive to the physical properties of the tephra-fallout deposit and the hydraulic and materiel strength properties of the study area. They both also show good agreement with field data but provide different information: TRIGRS provides an estimate of the timing (based on a storm event) and location of a potentially unstable area, while SHALSTAB simulations result in landslide susceptibility classes based on critical rainfall value. These outcomes provide fundamental insights into lahar triggering during long-lasting volcanic eruptions and are crucial to the compilation of lahar hazard maps and emergency management plans in the South Andes volcanic region. [ABSTRACT FROM AUTHOR]

Isopropylthioxanthone, a versatile photoinitiator (PI) for free radical photopolymerization (FRP), is combined with a triazine derivative (Tz) in a Type-II photoinitiating system (PIS). Initiation ability of this system for acrylate photopolymerization is assessed using a diacrylate monomer. Involvement of a photoinduced electron transfer mechanism is demonstrated by time-resolved spectroscopic measurements. Further insights in this mechanism are obtained through the use of a photopolymerization kinetic model taking into account the main reaction steps from the absorption of photons to the formation of the polymer. Prediction ability of the model is also tested with different initial concentrations of PI and co-initiator, as well as a different Tz. This last experiment reveals the noticeable role of back electron transfer in the FRP mechanism of Type-II PIS. [ABSTRACT FROM AUTHOR]

Reactive materials bring the dramatically enhanced lethality by means of the combined defeat mechanisms of impact kinetic energy and chemical energy release. This paper presents such an investigation on these reactive materials for the enhanced initiation behavior of covered explosives. First, a simple initiation process comparison between the inert metal and reactive material projectiles impacting covered explosives is described. Then high velocity ballistic impact experiments, which include both reactive material and tungsten alloy projectiles with mass matched against covered explosives, are conducted to investigate and compare the initiation behavior of covered explosives. Finally, theoretical analysis and discussions about contributions of both kinetic energy-to-initiation and chemical energy-to-initiation mechanisms to the enhanced initiation behavior of covered explosives impacted by reactive materials are presented. [ABSTRACT FROM AUTHOR]

During the May 12, 2008 Wenchuan earthquake, rock masses in the earthquake region were shaken, and subsequently, a number of post-earthquake landslides and debris flows occurred, triggered by heavy rainstorms. This paper presents a study of the rainfall-induced mechanism that triggered the landslides. This study is based on pre- and post-landslide geomorphology and geological features identified from pre-landslide high-resolution satellite imagery and post-landslide aerial photographs of the Wulipo landslide. The remote sensing observations were verified by field investigations. The results indicate that the heavy storm that occurred in July 2013 was the main trigger for the landslide although existing tensions and weak rock interfaces were the main internal causes for reactivation of the landslide. The bedding in the rocks dips in the same direction as the topographic slope. A tensile trough developed at the scarp. Based on data from the Wulipo rockslide, a model is proposed for calculating the safety factor for rockslides that takes into account the hydrostatic pressure along the structural plane of the rockslide. The results show that the proposed method can effectively estimate the stability of a storm-induced rockslide in regions underlain by bedded rocks. Based on this estimate, it is concluded that the Wulipo rockslide is a reactivated old rockslide. [ABSTRACT FROM AUTHOR]

A lot of irrigation systems have been established to promote agricultural production since the 1970s in the loess area of China. At the same time, the loess landslides increase because of the canal leakage. Gaoloucun landslide, located in Hua county of Shaanxi, China, is one of those landslides. In order to find the initiation mechanism, based on unsaturated permeability theory, a finite element model of the pre-failure slope was established to simulate the process of infiltration induced by water canal leakage. In order to find the stress state of slope failure, the loess samples were collected from the back edge of Gaoloucun landslide, and the triaxial tests of different stress paths under the saturation condition were performed. The triaxial tests include the stress path test on the possible sliding surface in the process of the increase of simulated water level, and the common load stress path test. The results show that because of the intermittent leakage, the perched water forms and rises in the slope, so that the pore water pressure in the saturated area increases, and the matric suction in the unsaturated area decreases; the rise of water level causes the initial deformation and damage, and the excess pore water pressure forms; the structure of loess soil at the top of the slope is loose, and the saturated water content is higher than the liquid limit, so that the saturated loess soil instantaneously changes from solid state to flow state, and the landslide is transformed into flow-slide. [ABSTRACT FROM AUTHOR]

Within the modern version of «Management 2.0» the approaches to the development of nonlinear starting mechanisms and maintenance of innovative self-development of organization on the example of regional business school are considered. It is noted that there are some possible models of behavior of regional business school among which the model focused on the activation of internal sources of development of the organization and its readiness to act as an infrastructure element of initiation of the self-development processes on the basis of openness, subjectivity and partnership. The business landscape of points of revitalization, results of initiation of activity and partnership form with the central concerned parties is offered. The effective partnership with science, authority, professional associations and business allows to create essentially new decisions for customer satisfaction. So, partner interaction with the client organizations is presented by new technology of joint creation of values in the form of project-focused training of innovative leaders and criteria of an assessment of its strategic productivity. The strategy of cultivating of mechanisms accepted by business school — attractors of innovative self-development is aimed at the formation of organization developing business — models of the new type typical for «2C-systems» (self-development and self-organizing systems).

Generally, the Al-PTFE is thought to be inert under quasi-static or static loads. However, it was recently found that after a specific heat treatment procedure Al-PTFE specimens could initiate under quasi-static compression. Sintering temperature, equivalence ratio and Al particle size were identified as three influencing factors of the initiation and were separately investigated by quasi-static compression tests, and reaction phenomena as well as stress–strain curves were recorded. Selected specimens were characterized by a scanning electron microscope (SEM). The results show that the sintering temperature controls the crystallinity of PTFE matrix, and the reactivity and toughness increase with the decreasing of crystallinity. The equivalence ratio affects the initiation as well as the propagation of reaction. Excessive Al particles would damage the continuity of the PTFE matrix, causing the decreasing of mechanical strength and reactivity. With the decreasing of Al particle size, the reactivity and toughness of Al-PTFE increase accordingly. A critical particle size exists between 3 μm and 14 μm, only below which the Al-PTFE could be initiated readily under quasi-static compression. A crack-induced initiation mechanism was proposed and was supported by SEM micrographs. [ABSTRACT FROM AUTHOR]

Debris flow is one of the major secondary mountain hazards following the earthquake. This study explores the dynamic initiation mechanism of debris flows based on the strength reduction of soils through static and dynamic triaxial tests. A series of static and dynamic triaxial tests were conducted on samples in the lab. The samples were prepared according to different grain size distribution, degree of saturation and earthquake magnitudes. The relations of dynamic shear strength, degree of saturation, and number of cycles are summarized through analyzing experimental results. The findings show that the gravelly soil with a wide and continuous gradation has a critical degree of saturation of approximately 87%, above which debris flows will be triggered by rainfall, while the debris flow will be triggered at a critical degree of saturation of about 73% under the effect of rainfall and earthquake (M>6.5). Debris flow initiation is developed in the humidification process, and the earthquake provides energy for triggering debris flows. Debris flows are more likely to be triggered at the relatively low saturation under dynamic loading than under static loading. The resistance of debris flow triggering relies more on internal frication angle than soil cohesion under the effect of rainfall and earthquake. The conclusions provide an experimental analysis method for dynamic initiation mechanism of debris flows. [ABSTRACT FROM AUTHOR]

The 2000 Yigong landslide was one of the most catastrophic landslides worldwide, resulting in huge casualties and property losses. The dynamic process of the Yigong landslide was very complicated, especially for the initiation and entrainment mechanism during the landslide movement process. The topography, geological condition, traces left by the landslide, and distribution characteristics of the landslide deposits were determined by field investigations, combined with several years of monitoring the temperature and rainfall data in this region. The initiation mechanism of the Yigong landslide is presented. The main reasons for the landslide initiation are as follows: the strength reduction of rock masses (especially for the weak structural surface), the impact from years of freeze-thaw cycles, the superposition of glacier melting and heavy rainfall on the slope, and a slope that was almost at the limit state before the landslide. Laboratory tests and physical modeling experiments were carried out to study the entrainment process of this landslide. Combined with the topographic survey data and theoretical analyses, the entrainment mechanism during the movement process of the Yigong landslide is presented. The old landslide deposits on the lower slope collided with and were scraped by the high-speed debris avalanche, which resulted in the volume amplification of the landslide. The existence of water plays a key role during the landslide initiation and movement processes. [ABSTRACT FROM AUTHOR]

In this paper, Chayuan gully was used as a model to investigate initiation of groovetype debris flow via rainfall experiments. The results show that: (1) under condition of heavy rainfall, infiltration rate and water content in soil are inversely proportional with rainfall intensity at different depths. Heavy rainfall is conducive to overland flow, gully runoff and incised erosion, but does not favour water infiltration; (2) mode of slope failure and debris flow initiation mechanism are various under different rainfall and runoff conditions. The slope failure mode presents soil liquefaction and landslide with rainfall intensity of 60 mm/h. Accordingly, initiation mechanism of debris flow is close to landslide conversion. However, gully beds are easy to be eroded and slopes are prone to collapse with heavy rainfall and runoff. Then, debris flows occurred with initiation mechanism of entrainment; (3) the characteristic of debris flow is that several intermittent flows will appear. In addition, debris flow magnitude and flow viscosity are not consistent with rainfall intensity with heavy rainfall. On the contrary, mudslides viscosity is smaller, high sand torrent appears more in trials. The experimental results are well consistent with the natural debris flow occurrence at Chayuan gully. [ABSTRACT FROM AUTHOR]

Debris flows usually occur abruptly and rapidly in mountainous areas and it is difficult to observe their occurrence progress. Therefore, an experiment has become an important method to study debris flow initiation mechanism in recent years. In this paper, taking Xiongjia Gully in SW China as an example and on the basis of artificial rainfall experiment, the author has studied the initiation of gully-type debris flow. Experiment results indicate some relation between rainfall intensity and gully erosion, failure mode of soil mass, initiation mechanism and characteristics of debris flow. Based on several groups of experiments, conclusions were drawn as follows: (1) Under strong precipitation, the infiltration rate and soil water content in different depths are inversely proportional to the rainfall intensity. Intense rainfall favors the overland flow, gully runoff and erosion, but is not conducive to water infiltration. (2) Slope failure modes and initiation mechanism of debris flow vary with different rainfall and runoff conditions. Under the condition with the rainfall intensity of 55 mm/h, the slope failure mode presents a soil liquefaction and landslide. Accordingly, the debris flow initiation mechanism belongs to landslide transformation. However, under the condition of intense rainfall and runoff, gully beds are easy to be eroded and slopes are prone to collapse. Then, debris flows occurred with initiation mechanism of entrainment. (3) In terms of debris flow characteristics, the debris flow occurrence process consists of several intermittent flows. In addition, the debris flow magnitude and flow viscosity are not consistent with rainfall intensity. On the contrary, under condition of intense rainfall of 65 and 75 mm/h, debris flows tend to be watery. However, under the rainfall condition of 55 mm/h, the flow viscosity is higher. The experiment results are consistent well with the natural debris flow occurrence from Xioangjia Gully. [ABSTRACT FROM AUTHOR]