Face Slab Research Articles

Settlement Prediction for Concrete Face Rockfill Dams Considering Major Factor Mining Based on the HHO-VMD-LSTM-SVR Model

Some important discoveries have been revealed in some studies, including that the settlement of concrete face rockfill dams (CFRDs) may cause cracks in the concrete face slabs, which may lead to dam collapse. Therefore, deformation behavior prediction of CFRDs is a longstanding and emerging aspect of dam safety monitoring. This paper aims to propose a settlement prediction model for CFRDs combining the variational mode decomposition (VMD) algorithm, long short-term memory (LSTM) network, and support vector regression algorithm (SVR). Firstly, VMD is applied in the decomposition of dam settlement monitoring data to reduce its complexity. Furthermore, feature information on settlement time series is extracted. Secondly, the LSTM and SVR are optimized by the Harris hawks optimization (HHO) algorithm and modified least square (PLS) method to mine the major influencing factors and establish the prediction model with higher precision. Finally, the proposed model and other models are applied to predict the deformation behavior of the Yixing CFRD. Prediction results indicate that the proposed method possesses particular advantages over other models. The proposed VMD-LSTM-SVR model might help to evaluate the settlement trends and safety states of CFRDs.

Early-age thermal cracking performance of carbon nanotube modified face slab concrete

The thermal cracking of face slab concrete (FSC) seriously affects the durability of face rockfill dams. The mechanical properties of carbon nanotubes such as high strength, excellent thermal conductivity provide great potential to improve the temperature cracking of the FSC. In this paper, the effects of CNTs on the thermal cracking resistance of the FSC at early ages were investigated in terms of mixture workability, pore structure, tensile modulus, and temperature stress testing machine test. It was demonstrated that the incorporation of 0.1 wt% CNTs significantly improved the pore structure of FSC and increased the tensile modulus of FSC at early ages. Besides, a model for the coefficient of thermal expansion (CTE) of FSC at early ages was established based on the temperature stress testing machine test, and the cracking comprehensive index, the cracking core index, and the cracking refinement index were compared. The incorporation of CNTs effectively reduced the CTE and the cracking temperature of FSC at early ages, and improved the ability of FSC to resist cracking in harsh environments. Therefore, CNTs exhibited a great potential to enhance the early-age cracking resistance performance of FSC.

Research on the slip deformation characteristics and improvement measures of concrete-faced rockfill dams on dam foundations with large dip angles

The pumped storage power station (PSPS) is an important measure to achieve the strategic goal of “dual carbon”. As one of the preferred types for the upper reservoir dams of PSPSs, the concrete-faced rockfill dam (CFRD) often has a dam foundation on a steep transverse slop and is prone to produce slip deformation along the slope, resulting in poor anti-sliding stability of the dam slope. It is dangerous for the operation safety of PSPSs. Therefore, the slip deformation of CFRDs on dam foundations with large dip angles is investigated. The mechanism for the initiation of slip deformation is revealed. The design measures of physical mechanic and geometric structure are proposed to reduce slip deformation. The results show that the larger sliding forces and smaller anti-sliding forces are the fundamental reasons that CFRDs on dam foundations with large dip angles are prone to produce slip deformation. The larger the dip angle of the dam foundation, the larger the slip deformation of the dam body and face slab, and the smaller the safety factor of the dam slope. When the dip angle of the dam foundation is greater than 15°, the safety factor of the dam slope is less than the minimum value of 1.5 required by codes. The addition of pressure slopes can effectively reduce the slip deformation of the dam body or face slab and significantly improve the anti-sliding stability of the dam slope. When the height or width of the pressure slope platform is greater and the cohesion or internal friction angle of the pressure slope is larger, the slip deformations of the dam body and face slab are smaller, and the safety factor of the dam slope is greater. It is recommended that the height and width of the pressure slope platform be 1/2 times the maximum height of the main dam, and the density (cohesion and internal friction angle) of the pressure slope be equivalent to that of the main dam’s rockfill material. The research results can provide theoretical and technical support for the design and construction of CFRDs for the upper reservoir of PSPSs.

High modulus partition deformation control of high concrete face rockfill dam

Concrete face rockfill dams, preferred for their adaptability in unloading and soft rock foundations, encounter significant deformation control challenges at increased heights. This study analyses the stress and strain of five Chinese dams, ranging from 179.5 m to 233.5 m, demonstrating improved structural responses by implementing high-modulus zones in the rockfill and concrete embedment. The findings reveal a direct relationship between rockfill settlement, concrete face slab deflection, and dam height. Incorporating a high-modulus zone and concrete embedment resulted in reduced rockfill settlement by 15% and 5.8%, concrete face slab deflection by 17% and 41.9%, and joint deformation by 10%–20% and 21.2%, respectively. This study is expected to support the deformation control of high-concrete-face rockfill dams.

Study on time-varying coefficient of thermal expansion of Carbon nanotubes-modified face slab concrete at early age

Temperature stresses are a major cause of thermal cracking in face slab concrete (FSC) at an early age. Time-varying coefficient of thermal expansion (CTE) can reflect the real thermal cracking of FSC. Carbon nanotubes (CNTs) can improve the mechanical properties of concrete, but its thermal cracking performance is rarely reported. In this study, CTE of FSC at an early age was investigated based on the maturity theory. The mechanism of CNTs on the CTE of FSC at early age was revealed, and a time-varying model for CTE at early age was developed. The results showed that CNTs can effectively reduce the CTE of FSC at an early age and can significantly improve the cracking resistance of FSC at early age.

A novel constitutive model for the concrete face slab of a CFRD and the numerical simulation of its seismic behavior

AbstractWith the rising demand for hydropower energy, China has built numerous concrete‐faced rockfill dams (CFRDs) with considerable heights. The potential failure pattern of the concrete face slab is the key to the safety of the anti‐seepage system. However, engineers commonly employ an elastic relationship to model the concrete face slab for simplicity, which induces inaccurate estimation of the face slab's stresses, especially under seismic conditions. On the other hand, the existing elastoplastic models for concrete often require complex derivation of the necessary formula and thus are difficult to apply to finite element (FE) analysis. Under the comprehensive action of the upstream water, supporting rockfill, and surrounding mountains, the damage mode of the quasibrittle concrete slab is not a tensile mode but a compressive shearing mode. Therefore, it is urgent to establish an elastoplastic model that is adapted to the actual working environment of the slab and easy to apply. To this end, a generalized plasticity model is developed within the phenomenology modeling concept, which is validated at both the experimental level and application level. The results indicate that three‐dimensional stress‒strain behaviors, such as the strength nonlinearity, prepeak dilatancy, and postpeak softening, can be effectively captured. In addition, the seismic characteristics of a 200‐m high CFRD are numerically investigated. The findings show that the slab's stress accumulation can be reflected during the earthquake and that the final stress distribution conforms to the field observations. The conclusions of this paper provide a reliable reference for the seismic resistance design of CFRDs.

Relationship between the distribution of intra-retinal hyper-reflective foci and the progression of intermediate age-related macular degeneration

PurposeTo assess the relationship between the distribution of intra-retinal hyper-reflective foci (IHRF) on optical coherence tomography (OCT) and progression of intermediate age-related macular degeneration (iAMD) over 2 years.MethodsCirrus OCT volumes of the macula of subjects enrolled in the Amish Eye Study with 2 years of follow-up were evaluated for the presence of iAMD and IHRF at baseline. The IHRF were counted in a series of 5 sequential en face slabs from outer to inner retina. The number of IHRF in each slab at baseline and the change in IHRF from baseline to year 2 were correlated with progression to late AMD at 2 years.ResultsAmong 120 eyes from 71 patients with iAMD, 52 eyes (43.3%) of 42 patients had evidence of both iAMD and IHRF at baseline. Twenty-three eyes (19.0%) showed progression to late AMD after 2 years. The total IHRF count increased from 243 at baseline to 604 at 2 years, with a significant increase in the IHRF number in each slab, except for the innermost slab 5 which had no IHRF at baseline or follow-up. The IHRF count increased from 121 to 340 in eyes that showed progression to late AMD. The presence of IHRF in the outermost retinal slabs 1 and 2 was independently associated with a significant risk of progression to late AMD. A greater increase in IHRF count over 2 years in these same slabs 1 and 2 was also associated with a higher risk of conversion to late AMD.ConclusionsThe risk of progression to late AMD appears to be significantly associated with the distribution and extent of IHRF in the outermost retinal layers. This observation may point to significant pathophysiologic differences of IHRF in inner versus outer layers of the retina.

Are inner nuclear layer ischemic lesions hidden indicators of retinal vein occlusion risk? A case-control study

PurposeTo investigate the association between retinal vein occlusion (RVO) and evidence of previous, unnoticed inner nuclear layer (INL) infarction in the fellow eye.MethodsThis prospective case-control study compared the prevalence of INL lesions in the fellow eye of consecutive people with hypertension (PwHTN) with unilateral RVO versus a randomly chosen eye of an age-matched control group of PwHTN without RVO. En face slabs above the outer plexiform layer (OPL) were generated from 6 × 6 fovea-centered optical coherence tomography scans. Cross-sectional scans and en face slabs were surveyed for evidence of active/resolved ischemic INL lesions.Results69 PwHTN were included and assigned to two groups, i.e., the RVO group (n = 37; 22 BRVO and 15 CRVO) and the control group (n = 32). There was no inter-group difference regarding age, gender distribution, and background diseases. Resolved INL lesions were more frequent in the RVO group (n = 26) than in the control group (n = 4) (70.3% vs. 12.5%, p < 0.001). BRVO and CRVO cases had similar prevalence of INL lesions in their fellow eyes. Unlike diabetes, ischemic heart disease, and gender, INL lesions were associated with RVO (in the fellow eye) with an odds ratio of 15.7 (95%CI: 4.17–76.73, p < 0.001).ConclusionWe identified a substantially higher prevalence of INL lesions in PwHTN with RVO compared to PwHTN without RVO. The atrophic appearance of lesions suggests they may serve as early markers of increased RVO risk in individuals with systemic or cardiovascular predisposing factors.

Monitoring Lesion Area Progression in Stargardt Disease: A Comparison of En Face Optical Coherence Tomography and Fundus Autofluorescence.

To compare longitudinal changes in en face spectral domain-optical coherence tomography (SD-OCT) measurements of ellipsoid zone (EZ) and retinal pigment epithelium (RPE) loss to changes in the hypoautofluorescent and hyperautofluorescent (AF) areas detected with short-wavelength (SW)-AF in ABCA4-associated retinopathy. SD-OCT volume scans were obtained from 20 patients (20 eyes) over 2.6 ± 1.2 years (range 1-5 years). The EZ, and RPE/Bruch's membrane boundaries were segmented, and en face slab images generated. SubRPE and EZ slab images were used to measure areas of atrophic RPE and EZ loss. These were compared to longitudinal measurements of the hypo- and abnormal AF (hypoAF and surrounding hyperAF) areas. At baseline, the en face area of EZ loss was significantly larger than the subRPE atrophic area, and the abnormal AF area was significantly larger than the hypoAF area. The median rate of EZ loss was significantly greater than the rate of increase in the subRPE atrophic area (1.2 mm2/yr compared to 0.5 mm2/yr). The median rate of increase in the abnormal AF area was significantly greater than the increase in the hypoAF area (1.6 mm2/yr compared to 0.6 mm2/yr). En face SD-OCT can be used to quantify changes in RPE atrophy and photoreceptor integrity. It can be a complementary or alternative technique to SW-AF with the advantage of monitoring EZ loss. The SW-AF results emphasize the importance of measuring changes in the hypo- and abnormal AF areas. The findings are relevant to the selection of outcome measures for monitoring ABCA4-associated retinopathy.

High Resolution Spectral Domain Optical Coherence Tomography of Multiple Evanescent White Dot Syndrome.

To evaluate a patient with multiple evanescent white dot syndrome (MEWDS) with multimodal imaging including high resolution spectral domain optical coherence tomography (SD-OCT). The patient was evaluated with wide-field color and autofluorescence imaging, microperimetry, and near infrared imaging. SD-OCT was performed using an instrument capable of 3 µm axial resolution, the High-Resolution Heidelberg Spectralis. 28 year-old woman developed photopsias and a scotoma in the field of vision of her left eye. She had multiple whitish spots with granularity in her fovea consistent with the diagnosis of MEWDS. She had supportive fluorescein angiographic and autofluorescence findings. Because of the high resolution and the good layer contrast, it was possible to create en face slab images of the external limiting membrane (ELM), the ellipsoid zone (EZ), interdigitation zone (IZ), and the retinal pigment epithelium (RPE). The ELM showed no abnormalities. There were multiple regions of decreased reflectance in the EZ slab, but even more prominent changes in the IZ. The RPE showed nearly no variation in layer reflectivity. With resolution of symptoms, the color and autofluorescence images returned to normal, the defects in the EZ almost completely resolved and the IZ continued to show abnormalities. Although past studies concluded the EZ was the main region of involvement in MEWDS, high resolution SD-OCT suggests the IZ was more prominently affected in this case.

A cross-scale finite element analysis of concrete-faced rockfill dam

In this paper, a new cross-scale finite element method is developed to study the mechanical response of concrete-faced rockfill dams, in which an arbitrary-node hexahedron element is used to deal with the mesh transition between the concrete slab and dam body. By using the proposed method, the mesh sizes of concrete slab and rockfill may be very different. Moreover, since the cross-scale method doesn't change the finite element calculation framework, the proposed method is easy to use. In the simulated CFRD, the mechanical behavior of the concrete slab is described by an elastic-plastic constitutive model, and a nonlinear elastic model is applied to the rockfill materials. The computational accuracy and performance of the proposed method are analyzed. The numerical results and analysis provides an effective approach to study the local behavior of concrete face slabs.

Overtopping-Induced breaching process of concrete-faced rockfill dam: A case study of Upper Taum Sauk dam

The back analysis of the dam breaching process based on reported failure case data is of great significance for understanding dam breaching mechanisms and the ability to predict breach flow hydrograph during emergencies. According to the essential information and post-failure investigation report of the Upper Taum Sauk dam, the first pumped storage power station in the United States, the most probable failure mechanism for dam breach is studied. Furthermore, a detailed physically-based numerical model is developed to simulate the overtopping-induced breach process of the concrete-faced rockfill dam (CFRD). Highlights of the model include the establishment of a simulation method of the dam-break flow based on the actual three-dimensional terrain considering the water-retaining characteristics of concrete face slabs, and the times and lengths of failure for each concrete face slab under water load and self-weight, as well as the adoption of different transportation modes for the widely graded rockfill materials. The breach side slope sliding mechanism is considered during the dam breach process. It is worth noting that the hydraulic features of dam-break flow and breach morphology can be well described with a combination of renormalization group (RNG) k-ε turbulence model and volume of fluid (VOF) method. The calculated results of the Upper Taum Sauk dam breaching parameters agree with the measured values, which testify to the rationality of the proposed model. The obtained time-varying dynamic dam breach process of CFRD can be divided into three stages. Moreover, the sensitivity analysis indicated that, the presence and absence of concrete face slabs affect the breach process of the Upper Taum Sauk dam significantly. The performance comparison with the existing dam breach models also verifies the advancement of the detailed physically-based model. Hence, the addressed numerical method can be used as an effective tool for simulating the CFRD breach process.

The influence of fiber on salt frost resistance of hydraulic face slab concrete

AbstractAs an important antiseepage structure of concrete face rockfill dam, the durability of concrete face slab is very important for the long‐term safe operation of the dam. Polypropylene fiber (PPF) and polyacrylonitrile fiber (PANF) are used as research objects to study the salt frost resistance of dual fiber Face slab concrete. The corrosion resistance of PPF and PANF concrete under different fiber volume was compared. The mass loss, residual compressive strength, relative dynamic modulus of elasticity and microstructure were evaluated in salt freezing environment. The results show that adding PPF and PANF to concrete can effectively improve the frost resistance of concrete, and the performance law is similar under the coupling failure of chloride and freeze–thaw cycles. Under the same volume, the effect of PPF concrete is more significant than PPF concrete, and the effect of adding two kinds of fibers at the same time is better than adding one fiber alone. Within the evaluation range, choosing 0.5% PPF and 0.5% PPF as additives is the best choice to improve the salt frost resistance. The results of scanning electron microscopy microstructure analysis of corrosion products are consistent with that of macro property analysis.

Measurement of the Macular Hole Diameter by En Face Slab Optical Coherence Tomography Reflectance Imaging.

PurposeTo evaluate the repeatability of macular hole (MH) diameter measurement on en face slab optical coherence tomography (OCT) reflectance images and assess its potential to predict visual acuity (VA).MethodsWe enrolled 27 eyes with full-thickness MHs in this study. Preoperative en face slab OCT reflectance images were obtained. Image binarization, ellipse approximation, and uncorrected measurement of minimum diameter, min(ef_uc), and maximum diameter, max(ef_uc), were performed using ImageJ. In addition, magnification-corrected diameters were calculated as min(ef) and max(ef) using the Littman and modified Bennett formulas. Spectral-domain OCT horizontal images were used as the conventional method for the analysis: min(conv) and max(conv). The inter-rater reliability of the method was evaluated by calculating the intraclass correlation coefficient (ICC). The following relationships were analyzed: (1) between logMAR VA and min(ef_uc), min(ef), and min(conv); and (2) between logMAR VA and max(ef_uc), max(ef), and max(conv).ResultsThe min(ef) and max(ef) values were 439.4 ± 240.5 µm and 720.7 ± 346.1 µm, respectively. The ICC values were 0.985 and 0.999 for min(ef) and max(ef), and 0.885 and 0.909 for min(conv) and max(conv), respectively. Multivariate analysis suggested that min(ef), but not min(ef_uc) or min(conv), was associated with pre- and postoperative logMAR VA. Furthermore, max(ef), but not max(ef_uc) or max(conv), was also closely correlated with pre- and postoperative logMAR VA.ConclusionsThe MH diameter measured by our method is highly reproducible and closely associated with VA compared to that measured by the conventional method.Translational RelevanceThe MH diameter measured by this modality might serve as an accurate biomarker to predict visual function in eyes with MH.

Influence of seismic wave type and incident direction on the dynamic response of tall concrete-faced rockfill dams

Owing to the stochastic behavior of earthquakes and complex crustal structure, wave type and incident direction are uncertain when seismic waves arrive at a structure. In addition, because of the different types of the structures and terrains, the traveling wave effects have different influences on the dynamic response of the structures. For the tall concrete-faced rockfill dam (CFRD), it is not only built in the complex terrain such as river valley, but also its height has reached 300 m level, which puts forward higher requirements for the seismic safety of the anti-seepage system mainly comprising concrete face slabs, especially the accurate location of the weak area in seism. Considering the limitations of the traditional uniform vibration analysis method, we implemented an efficient dynamic interaction analysis between a tall CFRD and its foundation using a non-uniform wave input method with a viscous-spring artificial boundary and equivalent nodal loads. This method was then applied to investigate the dynamic stress distribution on the concrete face slabs for different seismic wave types and incident directions. The results indicate that dam-foundation interactions behave differently at different wave incident angles, and that the traveling wave effect becomes more evident in valley topography. Seismic wave type and incident direction dramatically influenced stress in the face slab, and the extreme stress values and distribution law will vary under oblique wave incidence. The influence of the incident direction on slab stress was particularly apparent when SH-waves arrived from the left bank. Specifically, the extreme stress values in the face slab increased with an increasing incident angle. Interestingly, the locations of the extreme stress values changed mainly along the axis of the dam, and did not exhibit large changes in height. The seismic safety of CFRDs is therefore lower at higher incident angles from an anti-seepage perspective. Therefore, it is necessary to consider both the seismic wave type and incident direction during seismic capacity evaluations of tall CFRDs.

The Influence of Fly Ash Dosages on the Permeability, Pore Structure and Fractal Features of Face Slab Concrete

Concrete-face slabs are the primary anti-permeability structures of the concrete-face rockfill dam (CFRD), and the resistance of face slab concrete to permeability is the key factor affecting the operation and safety of CFRDs. Herein, the influences of five fly ash dosages (namely 10%, 20%, 30%, 40% and 50%) on the permeability property of face slab concretes were investigated. Moreover, the difference in the permeability caused by the fly ash dosage variations is revealed in terms of the pore structure and fractal theory. The results illustrate that: (1) The inclusion of 10–50% fly ash lowered the compressive strength of face slab concretes before 28 days of hydration, whereas it contributed to the 180-day strength increment. (2) The incorporation of 10–50% fly ash raised the average water-seepage height (Dm) and the relative permeability coefficient (Kr) of the face slab concrete by about 14–81% and 30–226% at 28 days, respectively. At 180 days, the addition of fly ash improved the 180-day impermeability by less than 30%. (3) The permeability of face slab concretes is closely correlated with their pore structures and Ds. (4) The optimal fly ash dosage in terms of the long-term impermeability and pore refinement of face slab concretes is around 30%. Nevertheless, face slab concretes containing a high dosage of fly ash must be cured for a relatively long period before they can withstand high water pressure.

Two-dimensional DEM-FEM coupling analysis of seismic failure and anti-seismic measures for concrete faced rockfill dam

The concrete faced rockfill dam is composed of granular materials and the failure pathways typically exhibits multi-scale mechanical behavior. In this paper, a 2D polygonal DEM-FEM interface coupling analysis program is developed and introduced to the failure analysis of a 100 m high CFRD under strong earthquake. The polygonal DEM is developed to describe the strong-nonlinearity, large deformation and discontinuous of dam. The FEM and seismic wave input method is combined to simulate the dam-foundation interaction. A boned model is proposed to describe the deformation characteristics of face slab and anti-seismic measure. The results indicate that the initial seismic failure of CFRD occurs at the crest zone, and is characterized by the loosening, sliding and even rolling away of the shallow rockfill on the slope. Other initial failure modes include settlement of the dam crest, separation between the face slab and rockfill, downstream sliding of the wave wall and separation between wave wall and face slab. The installation of a nailed protective slab at the upper part of the downstream slope reduces the seismic damage by 27–41 %. The analysis method can intuitively reproduce the seismic failure mode and failure evolution of the CFRD and quantify the effect of the anti-seismic measure.

Effects of Fly Ash Dosage on Shrinkage, Crack Resistance and Fractal Characteristics of Face Slab Concrete

The crack resistance of face slab concretes to various shrinkages is crucial for the structural integrity and the normal operation of concrete-faced rockfill dams (CFRDs). In this work, the effects of fly ash with four dosages (i.e., 10%, 20%, 30% and 40%) on the drying shrinkage, autogenous shrinkage and the cracking resistance of face slab concrete were studied. Besides, the difference in shrinkage behavior due to fly ash addition was revealed from the viewpoint of the pore structure and fractal dimension of the pore surface (Ds). The findings demonstrate that (1) the incorporation of 10–40% fly ash could slightly reduce the drying shrinkage by about 2.2–13.5% before 14 days of hydration, and it could reduce the drying shrinkage at 180 days by about 5.1–23.2%. By contrast, the fly ash addition could markedly reduce the autogenous shrinkage at early, middle and long-term ages. (2) Increasing fly ash dosage from 0 to 40% considerably improves the crack resistance of concrete to plastic shrinkage. Nevertheless, the increase in fly ash dosage increases the drying-induced cracking risk under restrained conditions. (3) The pore structures of face slab concrete at 3 and 28 days become coarser with the increase in fly ash dosage up to 40%. At 180 days, the pore structures become more refined as the fly ash dosage increases to 30%; however, this refinement effect is not as appreciable as the fly ash dosage increases from 30% to 40%. (4) The Ds of face slab concrete is closely related with the concrete pore structures. The Ds of face slab concrete at a. late age increases from 2.902 to 2.946 with increasing of the fly ash dosage. The pore structure and Ds are closely correlated with the shrinkage of face slab concrete. (5) The fly ash dosage around 30% is optimal for face slab concretes in terms of lowering shrinkage and refining the pore structures, without compromising much mechanical property. However, the face slab concretes with a large fly ash dosage should be well cured under restrained and evaporation conditions at an initial hydration age.

Cracking risk analysis of face slabs in concrete face rockfill dams during the operation period

Due to changes in the environmental load and deformation of rockfill bodies, cracks likely form and develop in the face slab of concrete face rockfill dams (CFRDs), affecting the working behaviour of face slabs and the safe operation of dams. At present, the cracking risk in face slabs has not been studied. Based on field test data and the finite element method, this paper developed a new method of analysing the cracking risk of face slabs. Considering that the uncertainty of construction quality leads to the randomization of rockfill material parameters, the probability function and coefficient of variation in the parameters of rockfill materials were determined based on field test data, and then, parameter samples were obtained by Latin hypercube sampling (LHS). The stress of the face slab was calculated by the Duncan-Chang E-B model and Burgers model with the parameter samples. To reduce the calculation workload of the finite element method based on traditional Monte Carlo samples, LHS and the long- and short-term memory (LSTM) algorithm were applied to obtain the response surface function. The LSTM algorithm was used to train the mapping relationship between the material parameters of the samples and the stress of the face slab. Combining the threshold value of the concrete allowable strength with the response surface method, the implicit cracking limit state function of the face slab was approximated, the cracking risk of the face slab was calculated, and the cracking risk curve of the typical area of the concrete face slab with time was given. In this case, mean absolute error (MAE) is 0.006 and the root mean square error (RMSE) is 0.004. The error of this method is very small, meeting the accuracy requirement. The case showed that the results were consistent with the inspection of the face slab and that the method was feasible and effective.

Optical coherence tomography angiography quantification of choriocapillaris blood-flow after half-fluence photodynamic therapy for chronic central serous chorioretinopathy.

To quantitatively analyze characteristics of choriocapillaris flow using spectral domain optical coherence tomography angiography (SD-OCTA) in eyes with chronic central serous chorioretinopathy (CSC) before and after treatment by photodynamic therapy (PDT). Retrospective interventional study. Macular 3X3 SD-OCT scans were analyzed in eyes diagnosed with chronic CSC before and after treatment with half-fluence PDT. The choriocapillaris en face slabs were extracted from the SD-OCTA device after manual segmentation. En face choriocapillaris flow images were compensated with en face choriocapillaris structure images. Phansalkar local thresholding method was then used with a radius of 4 and 8 pixels. Percentage of flow deficits (FD%), number, size, and total area of FDs were computed for comparison, before and after treatment by half-fluence PDT. Mean choriocapillaris FD% before PDT was of 58.36 + / - 11.88 and of 60.82 + / - 11.08 after PDT using radius 4 pixels with no significant difference (p = 0.140). Mean choriocapillaris FD% was of 58.63 + / - 11.08 before PDT and of 60.87 + / - 10.36 after PDT using radius 8 pixels with no significant difference (p = 0.200). Similarly, no significative difference was found in number, size, and total area of FDs, before and after half-fluence PDT, using radius 4 and 8 pixels in patients with chronic CSC. Using Phansalkar local thresholding method, quantitative analysis of choriocapillaris with SD-OCTA found no significant change in choriocapillaris flow deficits before and after successful half-fluence PDT in patients with chronic CSC. Therefore, it seems that half-fluence PDT may not alter choriocapillaris perfusion, at least on a relative short-term basis.