Nail Head Research Articles

Numerical Analysis on Stabilizing Mechanism of Soil Nails in Steep Fill Slopes Subjected to Rainfall Infiltration Using a Hypoplastic Model

Soil nailing has been widely used to stabilize slopes across the world over the last decades and is currently one of the predominant methods used for upgrading fill slopes in Hong Kong. The behavior of the soil nails in fill slopes has been investigated by experimental and numerical methods. However, the influence of rainfall infiltration on the reinforced fill slopes by soil nails was not investigated in existing studies. In addition, the stabilizing mechanism of the use of soil nails in fill slopes under rainfall condition is not yet understood thoroughly. The objectives of this study, therefore, are to explore the response of steep fill slopes to rainfall infiltration and the mechanism of soil nails in improving slope stability and reducing slope deformation. A series of two-dimensional numerical simulations where a hypoplastic constitutive model was used to model the strain-softening behavior of fill slopes was carried out. The numerical results show that a potential slide is developed in the unreinforced fill slope and thus slope failure may occur initiating from the toe of slope. Due to the presence of soil nails, both shallow failure and deep-seated failure are prevented in the soil nail reinforced slopes. The soil nails greatly limit the displacement of slope and the formation of potential slide in the slope. The tensile forces in the soil nails are mobilized through the effective interaction among soil nails, nail heads and surrounding soil when a potential slide is being initiated. The nail heads transfer the earth pressure of the overlying soil layer to the soil nails in question, causing the decrease of soil stress around the nail heads. The results also demonstrate that the interface friction between nail and soil can influence the stabilizing effect. Therefore, it is necessary to ensure sufficient interface friction to make the soil nails effective in transferring earth pressure and reducing slope deformation. However, once the friction coefficient between nail and soil reaches a threshold value, the interface friction will no longer be the key factor for the slope stability.

Evaluation of interface shear behavior of GFRP soil nails with a strain-transfer model and distributed fiber-optic sensors

A glass fiber reinforced polymer (GFRP) material is a newly developed material for slope reinforcement. In this study, distributed optical fiber sensors are developed to characterize the interface shear stress–strain behavior in GFRP soil nails with a strain-transfer model. The GFRP bar with a diameter of 40 mm was used as a reinforcing element in a soil slope subjected to excavations. A newly distributed fiber optic sensors are developed to measure the axial strains of the GFRP reinforcement which was then inserted into a drilled hole together with pressure grouting. The calibration of distributed fiber optic sensors indicated that the strains along the GFRP bar can be accurately measured by the distributed sensors. An analytical strain-transfer model is developed and then verified with a finite element model. The comparisons indicate that the strain-transfer model could be able to obtain the shear strain and stress at the cement grout–soil interface from arbitrary strain of the GFRP bar. Finally, a field project study is conducted for the condition assessment of a GFRP soil nail with the interface shear stress at different excavation depths. The potential failure surface is identified at the position where the maximum shear stress occurs, that is, at the point around 4.5 m away from the soil nail head. Results in terms of the shear stress are able to detect the active and passive zones of the soil nail. A further analysis indicates that the health condition of the GFRP soil nail can be determined with the distributed fiber sensors and strain-transfer model.

Pullout of soil nail with circular discs: A three-dimensional finite element analysis

An internal failure mode for a soil-nailed system consists of failure at nail heads, slope facing, nail strength, along grout–soil interface and pullout failure. A better understanding of pullout of soil nail thus becomes important to assess the stability of a soil-nailed system. In the present study, an investigation into the pullout behaviour of soil nail with circular discs along the shaft has been carried out by a three-dimensional finite element analysis using Abaqus/Explicit routine. A total of 67 simulations have been performed to accurately predict the pullout behaviour of soil nail. The soil nail under study has circular discs along its shaft varying in numbers from 1 to 4. The pullout of this soil nail in a pullout test box has been simulated with a constant overburden pressure of 20 kPa acting on the nail. The pullout load–displacement characteristics, stresses around soil nail and failure mechanism during pullout are studied. Variations of dimensionless factors such as normalised pullout load factor and bearing capacity factor have been obtained with different combinations of parameters in terms of relative disc spacing ratio, anchorage length ratio, embedment ratio, diameter ratio and displacement ratio. From the results of analyses, it is found that nail with more circular discs requires higher pullout load. There are critical relative disc spacing ratio and diameter ratio which significantly affect the pullout behaviour of nail.

Research on the reasonable pile spacing of micro pile composite soil nailing

Through the numerical simulation software FLAC3D, study on the synergetic effect of micro pile composite soil nailing will be studied. By adjusting the micro pile spacing and analysing the displacement field and stress field of soil, we can find that supporting effect of the soil nail hasn’t work yet when the micro pile spacing is 2D. The soil arching between piles has been formed in the pile spacing 4D ∼ 6D. The composite effect of micro pile and soil nailing will be the best and the soil arch behind piles will be firstly formed in 6D, the horizontal saddle soil arch will be formed between the nails. The nail head coincidence pressure area and micro pile pressure area are overlapping to maintain stability in the soil between piles. When the micro pile spacing is 9D, the arch behind piles will be failure, the soil flows around, but the saddle arch between the nails into circular arch, the supporting effect of the soil nailing is enhanced. When the micro pile spacing is 12D, the arch of the nails becomes smaller, sliding surface appears primitively. Based on the conclusions above, it is suggested that the micro pile spacing between 2D ∼ 6D is suitable for the micro pile and soil nailing composite support. The conclusion can provide theoretical basis for the design and construction of micro pile composite soil nailing.

Comparison of the effect of proximal femoral anti-rotation nail and artificial femoral head replacement with bone cement in the treatment of intertrochanteric fracture of femur in elderly patients

Objective To compare the efficacy of proximal femoral anti-rotation nail and artificial femoral head replacement with bone cement in the treatment of intertrochanteric fracture of femur in elderly patients. Methods 70 elderly patients with intertrochanteric fracture of femur were selected as the research subjects, and they were randomly divided into the observation group and the control group according to the digital table, 35 cases in each group.The observation group was treated with proximal femoral anti-rotation nail, the control group was treated with artificial femoral head replacement with bone cement.The clinical efficacy of the two groups was observed and compared. Results The operation time, intraoperative bleeding volume of the observation group were (52.63±13.72)min, (115.26±35.17)mL, respectively, which were significantly better than those of the control group[(86.69±21.15)min, (328.72±47.62)mL, t=3.98, 9.86, all P 0.05). There was no significant difference in the Harris hip score 30 months after operation between the two groups(t=0.18, P>0.05), while the Harris hip score of the observation group after 6 and 12 months were higher than those of the control group, the differences were statistically significant(t=9.04, 3.75, all P<0.05). Conclusion Compared with artificial femoral head replacement with bone cement, proximal femoral anti-rotation nail for elderly patients with intertrochanteric fracture of femur has more significant effect, it is worthy of clinical promotion. Key words: Femoral fractures; Fracture fixation, internal; Bone wires; Arthroplasty, replacement, hip; Aged

SCREW-IN SOIL NAIL FOR SLOPE REINFORCEMENT AGAINST SLIP FAILURE: A LAB-BASED MODEL STUDY

Slope failures occur when the shear resistance along the slip plane is exceeded. This can be caused by excessive load imposed at the slope crest or compromised stability of the slope, e.g. disturbed dimensions of the slope. In order to prevent slope failure, stabilisation or reinforcement measures need to be taken. A common solution is to intercept the slope failure plane with reinforcement elements, such as soil nails and ground anchors. In soil nailing, reinforcement bars are installed on the slope to effectively resist the additional shear forces from the imposed loads, hence reducing the probability of failure in the long run. This paper describes the innovation of soil nail with screw-in installation mechanism instead of the conventional push-in approach. The screw-in installation ensures better soil-nail grip and less disturbance during the slope stabilisation procedure, especially in terms of noise and spoils. In addition, the novel nail has a hollow stem which improves shear resistance with greater soil-nail surface contact on the inner wall. The opening at the nail head also enables displaced air to escape as the nail is screwed into the slope and soil pushed into the inner hollow cavity. The prototype nails were tested in a slope model with different configurations, and were found to reduce the Angular Distortion Ratio by 37 % and the Volumetric Deformation Index as much as 33 % respectively. The novel screw-in soil nail could be potentially used to stabilize natural and man-made slopes, though full-scale simulations are recommended to formulate the installation procedure and to validate the effectiveness.

The tool-wear characteristics of flexible printed circuit board micro-drilling and its influence on micro-hole quality

Purpose Micro-holes are drilled and plated in flexible printed circuit boards (FPCs) for connecting circuits from different layers. More holes, with diameters smaller than 0.3 mm, are required to be drilled in smaller areas with flexible circuits’ miniaturization. The micro-hole quality of micro-drilling is one of the biggest issues of the flexible circuit manufacturers’ production. However, it is not easy to control the quality of micro-holes. The purpose of this study was to conduct research on the tool wear characteristics of FPC drilling process and its influence on micro-hole quality to improve the micro-hole quality of FPC. Design/methodology/approach The tool-wear characteristics of micro-drills after FPC drilling were observed. The influence of spindle speed, feed rate, number of drilled holes and entry board materials on tool-wear was analyzed. The hole qualities of FPC micro-drilling were measured and observed. The relationship between tool-wear and hole quality was analyzed. Findings The result showed that the tool-wear characteristics of FPC micro-drilling was similar to the tool-wear characteristics of rigid printed circuit board (RPC) micro-drilling. Abrasive wear occurred on both the main cutting edges and the chisel edges of micro-drills, even though there was no glass fiber reinforcing the cloth inside FPC. Resin adhesion was observed on the chisel edge. The influence of feed and number of drilled holes on tool-wear was significant. Tool-wear significantly influences the hole quality of FPC. Tool-wear will largely decrease the hole position accuracy of FPC micro-holes. Tool-wear will increase the thickness of PI nail heads and the height of exit burrs. Fracture was the main difference between tool wear of FPC and RPC micro-drilling. Resin adhesion of RPC was much more severe than FPC micro-drilling. Increasing the spindle speed properly may improve tool life and hole quality. Originality/value The technology and manufacturing of FPC has been little investigated. Research on micro-drilling FPC and research data is lacking so far. The micro-hole quality directly affects the reliability of FPC. Thus, improving the micro-hole quality of FPC is very important.

Lasing in optimized two-dimensional iron-nail-shaped rod photonic crystals

We demonstrated lasing at the Γ-point band-edge (BE) modes in optimized two-dimensional iron-nail-shaped rod photonic crystals by optical pulse pumping at room temperature. As the radius of the rod increased quadratically toward the edge of the pattern, the quality factor of the Γ-point BE mode increased up to three times, and the modal volume decreased to 56% compared with the values of the original Γ-point BE mode because of the reduction of the optical loss in the horizontal direction. Single-mode lasing from an optimized iron-nail-shaped rod array with an InGaAsP multiple quantum well embedded in the nail heads was observed at a low threshold pump power of 160 μW. Real-image-based numerical simulations showed that the lasing actions originated from the optimized Γ-point BE mode and agreed well with the measurement results, including the lasing polarization, wavelength, and near-field image.

Effect of base metal and welding speed on fusion zone microstructure and HAZ hot-cracking of electron-beam welded Inconel 718

Influences of base metal and welding speed on fusion zone microstructure and heat affected zone (HAZ) hot-cracking of electron beam welded (EBW) Inconel 718 were investigated systematically. Microstructures of fusion zone and HAZ were characterized using the optical microscope and a field emission scanning electron microscope, complemented by the microhardness measurements. It is found that the weld shape transforms from a stemless wine glass shape to a nail head shape with the increase of the grain size of base metal. The largest amount of Laves or the lowest hardness is obtained in the center of the weld pool, which mainly due to the strong microsegregation in this region. The microsegregation of weld pool is significantly affected by welding speed, which is associated with the rate of transference of energy to the weld. The occurrence of HAZ cracking is related to the grain boundary and the generation of porosities is induced by fracture of the brittle carbides. Furthermore, the susceptibility of HAZ cracking is greatly dependent on the grain size of base metal and welding speed.

Evaluation of a modified technique for gamma nail removal

Question The indication for removing intramedullary nails in young patients is controversial. The principal reason for this is the comparably high OP morbidity, which basically results from the exposing of the nail head and may cause postoperative symptoms. The aim of this study was to develop a nail explantation technique that protects the bones and soft tissue, and then evaluate it in comparison to the conventional technique. Material and methods In the modified technique, the nail head is exposed via a targeting wire and the hand reamer of the nail instrumentarium under soft tissue protection, thus reducing the access morbidity compared to the conventional surgical method. The result of the operation was recorded based on a follow-up examination of the patients and the incision-suture time compared to the conventional operation. Results In the period from 5th September to 3rd October, the explantation was conducted with the new technique for 5 patients. The comparison ensued with 10 patients treated conventionally beforehand. The new technique revealed a significantly reduced mean OP time (31.0 against 74.8 minutes). All of the patients had less or no symptoms postoperatively in comparison to the findings before the metal removal. All of the patients stated that the operation had beneficial results for them. Conclusions The modified technique used in the operation with existing instrumentarium resulted both in a lowering of nail removal morbidity and a significant reduction in the operation time.

Microstructure and mechanical properties of laser-MAG hybrid welded thick-section weathered steel joint

Weathered steel (S355J2W) joint was prepared by laser-metal active gas hybrid welding technique. The microstructures of the joint were examined with an optical microscope and a scanning electron microscope. Microhardness measurement, tensile test, side bend test, and Charpy impact test were conducted to examine the mechanical properties of the joint. Experimental results show that S355J2W steel joint has a nail head shape with three different zones: weld metal, heat-affected zone (composed of overheated zone, normalized zone, and incomplete normalized zone), and base metal. The highest microhardness of the joint is 280 HV. All the joint specimens failed in the base metal. Average tensile strength of 502.6 MPa and yield strength of 380.9 MPa were achieved. A bending angle of 180° was obtained for all the joint specimens, and a crack less than 3 mm was detected. The average values of absorbed energy for the weld are 198.7 and 79.1 J at −40 and −20 °C, respectively. All the specimens exhibited a level of toughness as indicated by deformation at the fracture surface.

Modeling of keyhole dynamics and analysis of energy absorption efficiency based on Fresnel law during deep-penetration laser spot welding

Deep-penetration laser spot welding can effectively improve the utilization rate of the laser beam through forming the keyhole. In this paper, a model based on Fresnel law was developed with the computational fluid dynamics (CFD) software FLUENT. By considering the recoil pressure, surface tension, buoyancy and evaporation, a ray tracing technique was proposed to describe the absorption efficiency of the laser beam during the process of keyhole forming. It was found that there was large temperature gradient in the keyhole, recoil pressure and Marangoni flow forced the molten metal liquid to flow from bottom to top. At last it formed a nail head at the bottom and crowned at the top. The energy absorption efficiency rose from 42% to 59% during the keyhole forming, which was approximately linear with the depth of the keyhole.

Refined damage prediction of low-rise building envelope under high wind load

Since low-rise residential buildings are the most common and vulnerable structures in coastal areas, a reliable prediction of their performance under hurricanes is necessary. The present study focuses on developing a refined finite element model that is able to more rigorously represent the load distributions or redistributions when the building behaves as a unit or any portion is overloaded. A typical 5:12 sloped low-rise residential building is chosen as the prototype and analyzed under wind pressures measured in the wind tunnel. The structural connections, including the frame-to-frame connections and sheathing-to-frame connections, are modeled extensively to represent the critical structural details that secure the load paths for the entire building system as well as the boundary conditions provided to the building envelope. The nail withdrawal, the excessive displacement of sheathing, the nail head pull-through, the sheathing in-plane shear, and the nail load-slip are found to be responsible for the building envelope damage. The uses of the nail type with a high withdrawal capacity, a thicker sheathing panel, and an optimized nail edge distance are observed to efficiently enhance the building envelope performance based on the present numerical damage predictions.

쏘일 네일 두부 구속조건이 사면 안정성에 미치는 영향

Natural disasters such as earthquakes and tsunamis occur suddenly, so that they cause massive loss of lives and property. Especially earthquakes represent a particularly severe threat because of the extensive damage accompanied by them. In Korea, an earthquake-resistant design has been rarely applied to a design or construction of slope. However, in resent years, the researches for earthquake-resistance have been performed because the importance on the earthquake-resistance is perceived and highlighted. Soil nail method, one of the slope stability methods, is excellent for its constructability and cost effectiveness, as compared with other stability methods. Also, this method has been widely used for reinforced construction for slope stability. The studies of soil nail method have been performed on the interaction behavior between nails and slopes as well as the varied load condition such as static load, dynamic load and so on. Nevertheless, there has been minimal research regarding the constraint condition of nail head. In this study, the numerical analysis was performed for identifying effect on slope stability for the constrain condition of the soil nail. The result shows that the resistance of constrained the nail head on reinforced slope is larger compared to the one of unconstrained nail head.

Multiple Nail Gun Penetrating Head Injury: A Case Report

Intracranial nail gun injury is a rare subset of penetrating head injury. Here we report a case of intracranial nail gun injury in a Vietnamese patient who attempted suicide with no neurological deficit. Three nails were launched. Because the nail head acted as a brake, the launched nail could make a hole into the skull but could not entirely pass it. A rational management strategy should permit these patients to be discharged with no additional injury. Some medical and surgical management in penetrating head injury are discussed. The use of antibiotics and antiepileptic drugs and the retraction of the nail aided by the performance of a craniotomy surrounding the entry point are recommended.

Influence of number of finger joints per stud on mechanical performance of wood shearwalls

Finger-joined lumber studs are considered equivalent to, and can be used interchangeably with, unjoined lumber of the same grade in residential construction in Canada. However, there have been concerns expressed by engineers and users that there is no data available on the mechanical performance of shearwalls built with finger-joined studs to support this equivalency. This study was intended to address this information gap. Two groups of finger-joined studs were fabricated using ‘No. 2 or better’ grade spruce-pine-fir (SPF) lumber and a heat resistant polyvinyl acetate (PVA) adhesive. One group had 2–3 joints per stud, while the second group had 5–6 joints per stud. A control group of unjoined ‘No. 2 or better’ grade SPF lumber was sampled as a reference for comparison between groups. The stud dimensions were 38mm ×89mm×2.44m. Sheathing used was oriented strand board (OSB) panels with dimensions of 1.22m×2.44m×12.5mm. The stud frame was fastened using 12d common wire nails and the sheathing was fastened to the stud frame using 8d common wire nails. A total of 12 shearwall test specimens of dimensions 2.44m×2.44m were fabricated and tested. Test results showed that there was no statistically significant difference in the mechanical performance in terms of peak racking load and stiffness between shearwalls containing finger-joined studs (up to 5–6 joints) and shearwalls containing unjointed studs. The failure mode for each test wall was a combined sheathing nail withdrawal and sheathing nail head pull through. This study provides confirmation that finger-joined studs made using the PVA adhesive in this study could be deemed to be equivalent to unjoined studs in fabrication of shearwalls.

Influence of nail inclination and facing material type on soil-nailed slopes

The performance of a soil-nailed slope is significantly influenced by the slope geometry, nail parameters and facing material types. The objective of the present study was to examine the influence of nail inclination and facing material types on the stability and deformation behaviour of soil-nailed slopes subjected to seepage flow at 30g. A series of centrifuge model tests were carried out on 5V:1H slopes with and without soil nails. Bored and grouted soil nails including nail heads were modelled using thin aluminium tubes coated with a thin layer of sand-smeared adhesive. Two different nail inclinations of 10 and 25° with the horizontal were adopted with two different material facing types. All the models were thoroughly instrumented with displacement transducers for measuring surface settlements of the slope and pore pressure transducers to capture the development of the phreatic surface within the slope during the centrifuge test. In addition, the centre column of soil nails were instrumented at their mid-length to measure nail forces at the onset of seepage flow during the centrifuge test. A digital image analysis technique was employed to arrive at displacement vectors placed on the front elevation of the slope and markers attached to the facing to monitor face movements. Stability analysis of soil-nailed slopes with nail inclinations ranging from 0° to 30° in increments of 5° with the horizontal was carried out to ascertain optimum nail inclination for a 5V:1H slope with facing. The results indicate that stabilising the earth slope subjected to seepage using soil nails has a significant effect on the stability and deformation behaviour of the slope and is strongly influenced by nail inclination and the facing material type. For an identical type of facing and nail layout, a 5V:1H slope stabilised with soil nails inclined at 10° was observed to perform better than a slope stabilised with soil nails inclined at 25°. The measured nail forces were found to be on the higher side for a slope stabilised with soil nails inclined at 10° than at 25°. The observed centrifuge model tests were found to corroborate well with results of the slope stability analysis.

The essence of home

The essence of home Cheryl Weibye Wilke (bio) after Dan Pagis The essence of home is not a house, but a wall. Not eventhat, but a handful of nails. Not thirty, not even ten . . . not evena single nail head, just the shape of one—roundlike the world. [End Page 106] Cheryl Weibye Wilke Cheryl Weibye Wilke was born and raised on the small-town prairies of central Minnesota. Her award-winning poetry, and children's stories and articles, have graced numerous anthologies and literary magazines throughout the United States. Her first picture book is slated for publication by Raven Productions. Copyright © 2013 University of Nebraska Press

Three-Dimensional Modeling of Spatial Reinforcement of Soil Nails in a Field Slope under Surcharge Loads

Soil nailing has been one of the most popular techniques for improving the stability of slopes, in which rows of nails and a structural grillage system connecting nail heads are commonly applied. In order to examine the spatial-reinforcement effect of soil nails in slopes, a three-dimensional (3D) numerical model has been developed and used to back-analyze a field test slope under surcharge loading. Incremental elastoplastic analyses have been performed to study the internal deformation within the slope and the development of nail forces during the application of top surcharge loads. Different treatments of the grillage constraints at nail heads have been studied. It is shown that the numerical predictions compare favorably with the field test measurements. Both the numerical and the field test results suggest that soil nails are capable of increasing the overall stability of a loose fill slope for the loading conditions considered in this study. The axial force mobilization in the two rows of soil nails presents a strong dependence on the relative distance with the central section. With the surcharge loads increased near the bearing capacity of the slope, a grillage system connecting all the nail heads can affect the stabilizing mechanism to a notable extent.

Utilization of Agricultural Wastes in the Manufacture of Composite Boards

Development of useful composite materials out of agricultural waste has become a desirable option in recycling. This led to the production of composite boards being used in the construction industry. In this paper, three types of available agricultural wastes in the province of Batangas — peanut shells, corn husks and banana sheath — were independently utilized in the production of composite boards. The raw materials were either air or sun dried, then crushed (for peanut shells) and extracted (for banana sheath and corn husks) before mixing with the binder. Urea formaldehyde (UF) was used as binder for peanut shells and banana sheaths while cleaned used plastic bags were chopped and mixed with corn husks before subjecting to hot compress machine. For each mat, the followingproportions were used:1000 gm banana fibres, 500 gm of UF mixed with 250 gm of water; 720 gm of crushed peanut shells, 133 gm UF with 12% resin content; 40% corn husks, 60% plastic strips by weight. The physical and mechanical characteristics like modulus of rupture (MOR), internal bond, face screw head test (FSHT) or Nail Head Pull through (NHPT), water absorption and thicknessswelling were determined for each board and the results were compared to the values set by the Philippine National Standards (PNS). Based on statistical results, the corn husk-plastic composite boards conformed to all parameters in the PNS; the density, thickness swelling, IBS, and NHPT/ FSHT of peanut shell-resin composite boards conformed to the PNS; and the thickness swelling,density, MOR and NHPT/FSHT of the banana sheath-UF composite boards conformed to the PNS.