scholarly journals Incorporating Shear Stiffness into Post-Fire Debris Flow Triggering Models

2021 ◽  
Author(s):  
ROBB MOSS ◽  
Noah Lyman
Keyword(s):  
Debris Flow ◽  
Shear Failure ◽  
Shear Stiffness ◽  
Near Surface ◽  
Rainfall Events ◽  
Fire Debris ◽  
Improved Performance ◽  
Good Coverage ◽  
Type Response ◽  
Liquefaction Analysis

Abstract Current post-fire debris flow triggering models consider predictor variables accounting for; rainfall intensity, rainfall accumulation, area burned, burned intensity, geology, slope, and others. These models represent the physical process of debris flow initiation and subsequent shear failure by quantifying near-surface soil characteristics. By including shear wave velocity as a proxy for sediment shear stiffness, models can better inform the likelihood of particle dislocation, contractive or dilative volume changes, and downslope displacement that results from debris flows. This broadly available variable common to other hazard predictions, such as liquefaction analysis, provides good coverage in the watersheds of interest for debris flow predictions. A logistic regression is used to compare the new variable against currently used variables for predictive post-fire debris flow triggering models. We find that the new variable produces improved performance in prediction of triggering while capturing the physics of sediment failing in a shearing and flow-type response. Additional suggestions are presented for utilizing statistical cross-validation methods to advance prediction performance, and the utility of different variables for quick assessment of likelihood during eminent high intensity rainfall events.

EMERGENCY ASSESSMENT OF POST FIRE DEBRIS FLOW AND FLOODING HAZARDS, 2015 VALLEY AND BUTTE FIRES, CALIFORNIA

2016 ◽  
Author(s):  
Patrick K. Brand ◽  
◽  
David L. Longstreth ◽  
Jeremy T. Lancaster ◽  
William R. Short
Keyword(s):  
Debris Flow ◽  
Flooding Hazards ◽  
Fire Debris

DISTINGUISHING POST-FIRE DEBRIS FLOW EROSIONAL AND DEPOSITIONAL ZONES IN A BURNED WATERSHED

2019 ◽  
Author(s):  
Francis K. Rengers ◽  
◽  
Jason W. Kean ◽  
Dennis M. Staley ◽  
Luke McGuire
Keyword(s):  
Debris Flow ◽  
Fire Debris

scholarly journals “Seeing Is Believing”—In-Depth Analysis by Co-Imaging of Periodically-Poled X-Cut Lithium Niobate Thin Films

Crystals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 288
Author(s):  
Sven Reitzig ◽  
Michael Rüsing ◽  
Jie Zhao ◽  
Benjamin Kirbus ◽  
Shayan Mookherjea ◽  
...  
Keyword(s):  
Lithium Niobate ◽  
Second Harmonic ◽  
Imaging Techniques ◽  
Piezoresponse Force Microscopy ◽  
Periodically Poled ◽  
Near Surface ◽  
Domain Structures ◽  
Depth Analysis ◽  
Improved Performance ◽  
Quantum Optical

Nonlinear and quantum optical devices based on periodically-poled thin film lithium niobate (PP-TFLN) have gained considerable interest lately, due to their significantly improved performance as compared to their bulk counterparts. Nevertheless, performance parameters such as conversion efficiency, minimum pump power, and spectral bandwidth strongly depend on the quality of the domain structure in these PP-TFLN samples, e.g., their homogeneity and duty cycle, as well as on the overlap and penetration depth of domains with the waveguide mode. Hence, in order to propose improved fabrication protocols, a profound quality control of domain structures is needed that allows quantifying and thoroughly analyzing these parameters. In this paper, we propose to combine a set of nanometer-to-micrometer-scale imaging techniques, i.e., piezoresponse force microscopy (PFM), second-harmonic generation (SHG), and Raman spectroscopy (RS), to access the relevant and crucial sample properties through cross-correlating these methods. Based on our findings, we designate SHG to be the best-suited standard imaging technique for this purpose, in particular when investigating the domain poling process in x-cut TFLNs. While PFM is excellently recommended for near-surface high-resolution imaging, RS provides thorough insights into stress and/or defect distributions, as associated with these domain structures. In this context, our work here indicates unexpectedly large signs for internal fields occurring in x-cut PP-TFLNs that are substantially larger as compared to previous observations in bulk LN.

Observations and Analyses of the 9 January 2018 Debris-Flow Disaster, Santa Barbara County, California

2021 ◽  
Vol 27 (1) ◽  
pp. 3-27
Author(s):  
Jeremy T. Lancaster ◽  
Brian J. Swanson ◽  
Stefani G. Lukashov ◽  
Nina S. Oakley ◽  
Jacob B. Lee ◽  
...  
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Extreme Rainfall ◽  
Atmospheric Conditions ◽  
Santa Barbara ◽  
Debris Removal ◽  
Fire Debris ◽  
Santa Barbara County ◽  
Coastal Land

ABSTRACT The post–Thomas Fire debris flows of 9 January 2018 killed 23 people, damaged 558 structures, and caused severe damage to infrastructure in Montecito and Carpinteria, CA. U.S. Highway 101 was closed for 13 days, significantly impacting transportation and commerce in the region. A narrow cold frontal rain band generated extreme rainfall rates within the western burn area, triggering runoff-driven debris flows that inundated 5.6 km2 of coastal land in eastern Santa Barbara County. Collectively, this series of debris flows is comparable in magnitude to the largest documented post-fire debris flows in the state and cost over a billion dollars in debris removal and damages to homes and infrastructure. This study summarizes observations and analyses on the extent and magnitude of inundation areas, debris-flow velocity and volume, and sources of debris-flow material on the south flank of the Santa Ynez Mountains. Additionally, we describe the atmospheric conditions that generated intense rainfall and use precipitation data to compare debris-flow source areas with spatially associated peak 15 minute rainfall amounts. We then couple the physical characterization of the event with a compilation of debris-flow damages to summarize economic impacts.

Fracture of Sifcon Under Combined Tensile and Shearlike Loading

1990 ◽  
Vol 211 ◽  
Author(s):  
J. G. M. Van Mier
Keyword(s):  
Shear Failure ◽  
Crack Opening ◽  
Shear Stiffness ◽  
Fiber Direction ◽  
Axial Tension ◽  
Crack Band ◽  
Fiber Concrete ◽  
Axial Crack ◽  
Fiber Action ◽  
Inclined Cracks

AbstractIn a series of preliminary experiments, the shear stiffness degradation and ’shear’ failure mechanisms of pre-cracked Slurry Infiltrated Fiber CONcrete (SIFCON) were studied. The specimens were first subjected to axial tension (in displacement control), whereafter a lateral shear was applied over the crack band. Variables in the investigation were the direction of loading with regard to the main fiber direction, and the axial crack opening before shearing. The degradation of shear stiffness resembles that of normal concrete at low crack openings, but seems governed by fiber action at larger crack openings. At low crack openings, shear failure was observed in the sense of an array of inclined tensile microcracks. At larger crack openings, inclined cracks developed through coalescence of preexisting tensile cracks.

scholarly journals Investigation of a New Strengthening Technique for RC Deep Beams Using Carbon FRP Ropes as Transverse Reinforcements

Fibers ◽  
2018 ◽  
Vol 6 (3) ◽  
pp. 52 ◽  
Author(s):  
Constantin Chalioris ◽  
Parthena-Maria Kosmidou ◽  
Nikos Papadopoulos
Keyword(s):  
Shear Failure ◽  
Structural Behaviour ◽  
Deep Beams ◽  
Near Surface ◽  
Lap Splices ◽  
Rectangular Beam ◽  
Rc Deep Beams ◽  
Carbon Fibre Reinforced Polymer ◽  
Strengthening Technique ◽  
The Web

The effectiveness of a new retrofitting technique to upgrade the structural behaviour of reinforced concrete (RC) deep beams without steel stirrups using carbon fibre-reinforced polymer (CFRP) ropes as the only transverse shear reinforcement is experimentally investigated. Five shear-critical beams with rectangular and T-shaped cross-section are tested under monotonic loading. The strengthening schemes include (a) one vertical and one diagonal single-link CFRP rope that are internally applied through the web of the rectangular beam using an embedded through-section (ETS) system and (b) two vertical U-shaped double-link ropes that are applied around the perimeter of the web of the flanged beam using a near-surface-mounted (NSM) system. In both cases, the free lengths of the CFRP ropes have been properly anchored using epoxy bonded lap splices of the rope as NSM at (a) the top and the bottom of the web of the rectangular beam and (b) the top of the slab of the T-beam. Promising results have been derived, since the proposed strengthening technique enhanced the strength and altered the brittle shear failure to a ductile flexural one. The experimental results of this study were also used to check the validity of an analytical approach to predict the strength of shear strengthened deep beams using FRP ropes as transverse link reinforcement.

scholarly journals Peak Discharge and Hydrograph Assessments Induced by Heavy Rainfall Events Using Tank Model

2018 ◽  
Vol 207 ◽  
pp. 02001
Author(s):  
Yen-Kun Hsu ◽  
Szu-Hsien Peng ◽  
Chiao-Wen Tsai
Keyword(s):  
Debris Flow ◽  
Flow Simulation ◽  
Rain Gauge ◽  
Peak Discharge ◽  
Soil Horizon ◽  
Tank Model ◽  
Rainfall Events ◽  
The Mean ◽  
Heavy Rainfall Events ◽  
Better Than

Tank Model is a kind of simulation of rainfall movement in soil horizon. With the runoff and piping rate, the peak discharge could be effectively calculated. Having 17 rain gauge stations in 13 debris flow events during 1996-2010 as the studied cases, the peak discharge at 12 control points along Chenyulan River is simulated. Furthermore, the data in Neimaopu discharge station is established parameters of Tank Model to estimate the peak discharge in Shenmu Village. By comparing with the parameters of Shueili Station and Japanese Granite, the mean error of the parameter in this study is 51.0%, which is better than those of Japanese Granite 189% and Shueili discharge stations 251%. The parameter in this study appears the highest in allowance analysis, showing that it is more suitable for simulating the peak discharge than the other two. In spite that the percentage of the three parameters is still low, Shenmu Village could be ignored as it locates in the sub-basin of Chenyulan River with few factors. The parameters of Tank Model are applied to transform average rainfall into hydrograph so as to solve the problem of no discharge records when analysing the areas with various debris flow simulation programs.

scholarly journals Inundation, flow dynamics, and damage in the 9 January 2018 Montecito debris-flow event, California, USA: Opportunities and challenges for post-wildfire risk assessment

Geosphere ◽  
2019 ◽  
Vol 15 (4) ◽  
pp. 1140-1163 ◽  
Author(s):  
J.W. Kean ◽  
D.M. Staley ◽  
J.T. Lancaster ◽  
F.K. Rengers ◽  
B.J. Swanson ◽  
...  
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Field Measurements ◽  
Economic Loss ◽  
Flow Dynamics ◽  
Dynamic Constraints ◽  
Fire Debris ◽  
Velocity Information ◽  
Intense Burst ◽  
Comprehensive Framework

Abstract Shortly before the beginning of the 2017–2018 winter rainy season, one of the largest fires in California (USA) history (Thomas fire) substantially increased the susceptibility of steep slopes in Santa Barbara and Ventura Counties to debris flows. On 9 January 2018, before the fire was fully contained, an intense burst of rain fell on the portion of the burn area above Montecito, California. The rainfall and associated runoff triggered a series of debris flows that mobilized ∼680,000 m3 of sediment (including boulders >6 m in diameter) at velocities up to 4 m/s down coalescing urbanized alluvial fans. The resulting destruction (including 23 fatalities, at least 167 injuries, and 408 damaged homes) underscores the need for improved understanding of debris-flow runout in the built environment, and the need for a comprehensive framework to assess the potential loss from debris flows following wildfire. We present observations of the inundation, debris-flow dynamics, and damage from the event. The data include field measurements of flow depth and deposit characteristics made within the first 12 days after the event (before ephemeral features of the deposits were lost to recovery operations); an inventory of building damage; estimates of flow velocity; information on flow timing; soil-hydrologic properties; and post-event imagery and lidar. Together, these data provide rare spatial and dynamic constraints for testing debris-flow runout models, which are needed for advancing post-fire debris-flow hazard assessments. Our analysis also outlines a framework for translating the results of these models into estimates of economic loss based on an adaptation of the U.S. Federal Emergency Management Agency’s Hazus model for tsunamis.

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