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This study compiles a broad database containing 312 measured maximum soil nail loads under operational conditions. The database is used to re-assess the prediction accuracies of the default Federal Highway Administration (FHWA) nail load model and its modified version previously reported in the literature. Predictions using the default and modified FHWA models are found to be highly dispersive. Moreover, the prediction accuracy is statistically dependent on the magnitudes of the predicted nail load and several model input parameters. The modified FHWA model is then recalibrated by introducing extra empirical terms to account for the influences of wall geometry, nail design configuration, and soil shear strength parameters on the evolvement of nail loads. The recalibrated FHWA model is demonstrated to have much better prediction accuracy compared to the default and modified models. Next, an artificial neural network (ANN) model is developed for mapping soil nail loads, which is shown to be the most advantageous one as it is accurate on average and the dispersion in prediction is low. The abovementioned dependency issue is also not present in the ANN model. The practical value of the ANN model is highlighted by applying it to reliability-based designs of soil nails against internal limit states. Key words: soil nail wall, maximum nail load, artificial neural network, model uncertainty, reliability-based design. Cette etude compile une vaste base de donnees contenant 312 charges maximales mesurees de clous de sol dans des conditions operationnelles. La base de donnees est utilisee pour reevaluer l'exactitude des previsions du modele de charge de clouage par defaut de la Federal Highway Administration (FHWA) et de sa version modifiee precedemment rapportee dans la litterature. Les predictions utilisant le modele par defaut et le modele modifie de la FHWA s'averent tres dispersives. De plus, la precision de la prediction depend statistiquement de l'amplitude de la charge prevue des clous et de plusieurs parametres d'entree du modele. Le modele modifie de la FHWA est ensuite recalibre en introduisant des termes empiriques supplementaires pour tenir compte des influences de la geometrie des Mursla configuration de la conception des clous et les parametres de resistance au cisaillement du sol sur revolution de la charge des clous. Il a ete demontre que le modele de la FHWA recalibre a une bien meilleure precision de prediction que le modele par defaut et le modele modifie. Ensuite, un modele de reseau neuronal artificiel (ANN) est developpe pour cartographier les charges de clous du sol, qui s'avere etre la plus avantageuse car elle est precise en moyenne et la dispersion dans la prediction est faible. Le probleme de dependance susmentionne n'est pas non plus present dans le modele ANN. La valeur pratique du modele ANN est mise en evidence en appliquant aux conceptions fondees sur la fiabilite des clous de sol aux etats limites internes. [Traduit par la Redaction] Mots-cles : paroi des ongles du sol, charge maximale des ongles, reseau neuronal artificiel, incertitude du modele, conception basee sur la fiabilite., 1. Introduction As one of the most cost-effective, time-efficient reinforcing techniques, soil nailing has been widely used to stabilize cut slopes, pit excavations, railway embankments, shorelines, etc. (GEO 2008; Griggs [...]

This paper demonstrates reliability-based design for tensile rupture and pullout limit states for mechanically stabilized earth (MSE) walls constructed with geosynthetic (geogrid) reinforcement. The general approach considers the accuracy of the load and resistance models that appear in each limit state equation plus uncertainty due to the confidence (level of understanding) of the designer at the time of design. The reliability index is computed using a closed-form solution that is easily implemented in a spreadsheet. The general approach provides a quantitative link between nominal factor of safety, which is familiar in allowable stress design practice, and reliability index used in modern civil engineering reliability-based design practice. A well-documented MSE wall case study is used to demonstrate the general approach and to compare margins of safety using different load and resistance model combinations. A practical outcome from the case study example is the observation that the pullout limit state is much less likely to control design than the ultimate tensile rupture state for walls with continuous reinforcement coverage. The more accurate 'simplified stiffness method' that is used to compute tensile loads in the reinforcement under operational conditions is shown to generate a more cost-effective reinforcement option than the less accurate American Association of State Highway and Transportation Officials (AASHTO) simplified method. Key words: mechanically stabilized earth (MSE) walls, geosynthetic reinforcement, internal stability limit states, reliability-based design. Cet article demontre une conception basee sur la fiabilite pour les etats limites de rupture en traction et darrachement pour les murs de terre stabilises mecaniquement (<>) avec un renforcement geosynthetique (geogrille). L'approche generale considere la precision des modeles de charge et de resistance qui apparaissent dans chaque equation d'etat limite plus l'incertitude due a la confiance (niveau de comprehension) du concepteur au moment de la conception. L'indice de fiabilite est calcule a l'aide d'une solution analytique facilement implementee dans une feuille de calcul. L'approche generale fournit un lien quantitatif entre le facteur de securite nominal connu dans la pratique de la conception des contraintes admissibles et l'indice de fiabilite utilise dans les pratiques de conception basee sur la fiabilite du genie civil moderne. Une etude de cas MSE bien documentee est utilisee pour demontrer l'approche generale et pour comparer les marges de securite en utilisant differentes combinaisons de modeles de charge et de resistance. Un resultat pratique de l'exemple de l'etude de cas est l'observation selon laquelle l'etat limite d'arrachement est beaucoup moins susceptible de controler la conception que l'etat de rupture en traction ultime pour les murs a couverture continue. La methode de rigidite simplifiee la plus precise utilisee pour calculer les charges de traction dans le renforcement dans des conditions operationnelles est montree comme generant une option de renforcement plus rentable que la methode simplifiee << American Association of State Highway and Transportation Officials >>(AASHTO) moins precise. [Traduit par la Redaction] Mots-cles : murs de terre stabilises mecaniquement (MSE), renforcement geosynthetique, etats limites de stabilite interne, conception basee sur la fiabilite., 1. Introduction The internal stability design of mechanically stabilized earth (MSE) walls in North America is most often based on load and resistance factor design (LRFD) which is a reliability [...]

The accuracy of the default Federal Highway Administration (FHWA) simplified model for estimation of facing tensile forces for soil nail walls under in-service conditions was evaluated using a large quantity of measured long-term and short-term facing tensile force data collected from the literature. The estimation accuracy was quantified by the mean and coefficient of variation (COV) of the bias where bias is defined as the ratio of measured to calculated facing tensile force. Based on the available data, the default FHWA simplified model equation was found to overestimate long- and short-term facing tensile forces by about 15% and 23% on average, respectively. The corresponding spreads in estimation accuracy expressed as the bias COV were about 43% and 67%. Undesirable correlations between bias values and calculated facing tensile forces using the default FHWA simplified model equation were detected. A modified FHWA simplified model was proposed to improve the on average accuracy, reduce the spread in estimation accuracy, and remove the hidden correlations noted above. In addition, the modified equation has fewer empirical coefficients than the current formulation (i.e., four versus five). The facing tensile force equations developed in this study are a contribution to the design of facing of soil nail walls within the current FHWA soil nail wall design framework. Key words: soil nail walls, facing tensile forces, Federal Highway Administration (FHWA) simplified models, statistical analysis, model bias. La precision du modele simplifie par defaut de la Federal Highway Administration (FHWA) pour revaluation des forces de traction au parement de mur de clous de sol dans des conditions de service a ete evaluee en utilisant un grand nombre de donnees de force de traction de la litterature, mesurees a court et a long terme. La precision de l'estimation a ete quantifiee par la moyenne et le coefficient de variation (COV) du biais, ou le biais est defini comme le rapport entre la force de traction au parement mesuree et calculee. Sur la base des donnees disponibles, il s'est avere que l'equation par defaut du modele simplifie FHWA a surestime les forces de traction au parement a long et a court terme par environ 15 et 23 % en moyenne, respectivement. Les ecarts correspondants au niveau de la precision de l'estimation exprimee par le biais COV etaient d'environ 43 et 67 %. Des correlations indesirables entre les valeurs de biais et les forces de traction au parement calculees ont ete detectees en utilisant l'equation du modele simplifie FHWA par defaut. Un modele simplifie FHWA modifie a ete propose pour ameliorer la precision moyenne, reduire l'ecart au niveau de la precision de l'estimation et supprimer les correlations cachees mentionnees ci-dessus. De plus, l'equation modifiee a moins de coefficients empiriques que la formulation actuelle (c'est-a-dire, quatre contre cinq). Les equations de la force de traction au parement, developpee dans cette recherche sont une contribution a la conception du revetement des parois d'ancrage de sol dans le cadre actuel de la conception d'ancrage de sol FHWA. [Traduit par la Redaction] Mots-cles: clou de sol, forces de traction au parement, modeles simplifies FHWA, analyses statistiques, modele biais., Introduction Soil nail walls are widely used to support both temporary and permanent excavations. Typically, the facing of a soil nail wall is constructed immediately after installation of nails at [...]

Cross correlations between nominal load and resistance terms in limit state functions for geotechnical soil-structure interaction problems can be expected. A closed-form solution for the reliability index for a simple linear limit state function is used to examine the influence of nominal load and resistance correlations on computed margins of safety. The formulation also includes the contribution of the underlying accuracy of the load and resistance equations (method bias) and bias dependencies with the magnitude of nominal load and resistance values assumed in the limit state design function. Sensitivity analyses and example problems for the external sliding limit state for a cantilever wall and the pullout limit state for internal stability of reinforced soil walls with different soil reinforcement types are presented. Ignoring nominal correlations where they exist is shown to underestimate the reliability index in some cases and to overestimate the reliability index in other cases. In the example problems, these differences are shown to exceed one order of magnitude in terms of probability of failure, but in the sensitivity analyses using a wider range of input parameter values, the differences can be several orders of magnitude. Key words: geotechnical soil-structure interaction, reliability-based design, linear limit state, nominal correlation, bias dependency, sliding, pullout. Les correlations croisees entre la charge nominale et la resistance en termes de fonctions d'etat limite geotechnique pour les problemes d'interaction sol-structure peuvent etre prevues. Une solution a forme fermee pour l'indice de fiabilite pour une fonction d'etat limite lineaire simple est utilisee pour examiner l'influence de la charge nominale et de la resistance sur les correlations calculees des marges de securite. La formulation comprend egalement la contribution de l'exactitude des equations de charge et de resistance (methode de polarisation) et du biais les dependances avec l'ampleur de la charge nominale et les valeurs de resistance a l'etat suppose a limiter la fonction de conception. Des analyses de sensibilite et l'exemple des problemes pour l'etat limite de glissement externe pour un mur a porte a faux et l'etat limite d'arrachement pour la stabilite interne des murs de terre renforcee avec differents types de renforcement des sols sont presentes. Ignorant les correlations nominales lorsqu'ils existent est montre a sous-estimer l'indice de fiabilite dans certains cas et a surestimer l'indice de fiabilite dans les autres cas. Dans l'exemple des problemes, ces differences sont presentees pour depasser un ordre de grandeur en termes de probabilite d'echec, mais dans les analyses de sensibilite en utilisant un plus large eventail de valeurs de parametre d'entree, les differences peuvent etre de plusieurs ordres de grandeur. [Traduit par la Redaction] Mots-cles : interaction sol-structure geotechnique, conception basee sur la fiabilite, etat limite lineaire, correlation nominale, dependance biaisee, coulissant, retire., Introduction Geotechnical engineers are often faced with simple soil-structure interaction problems in which the same input parameter definitions appear in both load and resistance terms of a limit state function. [...]

The effective length of soil nails is one of the critical parameters ensuring the reinforcing effect, and its accurate estimation is of great significance for the safety of the slope and deep foundation pit supporting projects. Traditional quality insurance methods, such as nail pullout tests, suffer from a series of drawbacks including being destructive, high cost, and time-consuming. In contrast, non-destructive testing (NDT) has been increasingly applied in various engineering fields in the past decades given its advantages of not damaging the material and easy operation. However, the current application of NDT in soil nail length measurement is relatively limited, and its accuracy and reliability are yet to be quantitatively evaluated. This paper introduces three methods for estimating soil nail length based on guided wave theory and collects 116 sets of NDT data for nail length. The accuracy of the NDT in soil nail prediction is statistically analyzed using the model bias method. The results show that those methods can accurately predict the nail length with an average error of less than 3% and a low dispersion of 12%. The accuracy of the NDT methods is not affected by the hammer type or estimation method. Furthermore, this paper proposes a model calibration to the original NDT method, which improves the model's average accuracy by 3% and reduces dispersion by 4% without increasing computational complexity. Finally, the probability distributions of the model biases are characterized. This study can provide practical tools for fast estimation of in situ nail length, which is of high significance to supporting slopes and deep foundation pits. [ABSTRACT FROM AUTHOR]

The facing is a key component for the design of soil nail walls. However, current design specifications of soil nail walls in China do not specify methods for estimation of facing tensile forces, which has posed challenges for engineers to produce consistent, safe, and cost-effective facing designs. This study first constructs the facing tensile force as the product of the maximum nail load and a facing factor. Then a database containing 91 measured facing tensile force data collected from the literature is developed and used to calibrate the facing factor matching six maximum nail load models that are commonly adopted in China, namely, the simplified incremental calculation models based on the Rankine and Coulomb earth pressure theories, the China Academy of Building Research model, and the China Association for Engineering Construction Standardization model. Based on the developed database, the accuracies of the six proposed models for facing tensile forces are demonstrated to be unbiased on average and the dispersions in the prediction accuracy are ranked from low to medium. Furthermore, the influences of three wall working conditions on prediction accuracy of the developed models are investigated and shown to be practically insignificant. Last, the model biases are characterised as lognormal random variables. [ABSTRACT FROM AUTHOR]

Colony-stimulating-factor-1 (CSF-1) signaling through cFMS receptor kinase is increased in several diseases. To help investigate the role of cFMS kinase in disease, we identified GW2580, an orally bioavailable inhibitor of cFMS kinase. GW2580 completely inhibited human cFMS kinase in vitro at 0.06 [micro]M and was inactive against 26 other kinases. GW2580 at 1 [micro]M completely inhibited CSF-1-induced growth of mouse M-NFS-60 myeloid cells and human monocytes and completely inhibited bone degradation in cultures of human osteoclasts, rat calvaria, and rat fetal long bone. In contrast, GW2580 did not affect the growth of mouse NS0 lymphoblastoid cells, human endothelial cells, human fibroblasts, or five human tumor cell lines. GW2580 also did not affect lipopolysaccharide (LPS)-induced TNF, IL-6, and prostaglandin E2 production in freshly isolated human monocytes and mouse macrophages. After oral administration, GW2580 blocked the ability of exogenous CSF-1 to increase LPS-induced IL-6 production in mice, inhibited the growth of CSF-1-dependent M-NFS-60 tumor cells in the peritoneal cavity, and diminished the accumulation of macrophages in the peritoneal cavity after thioglycolate injection. Unexpectedly, GW2580 inhibited LPS-induced TNF production in mice, in contrast to effects on monocytes and macrophages in vitro. In conclusion, GW2580's selective inhibition of monocyte growth and bone degradation is consistent with cFMS kinase inhibition. The ability of GW2580 to chronically inhibit CSF-1 signaling through cFMS kinase in normal and tumor cells in vivo makes GW2580 a useful tool in assessing the role of cFMS kinase in normal and disease processes. CSF-1 | macrophage colony-stimulating factor