The human Vδ2⁺ T-cell compartment comprises distinct innate-like Vγ9⁺ and adaptive Vγ9^- subsets

Vδ2+ T cells form the predominant human γδ T-cell population in peripheral blood and mediate T-cell receptor (TCR)-dependent anti-microbial and anti-Tumour immunity. Here we show that the Vδ2+ compartment comprises both innate-like and adaptive subsets. Vγ9+ Vδ2+ T cells display semi-invariant TCR repertoires, featuring public Vγ9 TCR sequences equivalent in cord and adult blood. By contrast, we also identify a separate, Vγ9- Vδ2+ T-cell subset that typically has a CD27hiCCR7+CD28+IL-7Rα+ naive-like phenotype and a diverse TCR repertoire, however in response to viral infection, undergoes clonal expansion and differentiation to a CD27loCD45RA+CX3CR1+granzymeA/B+ effector phenotype. Consistent with a function in solid tissue immunosurveillance, we detect human intrahepatic Vγ9- Vδ2+ T cells featuring dominant clonal expansions and an effector phenotype. These findings redefine human γδ T-cell subsets by delineating the Vδ2+ T-cell compartment into innate-like (Vγ9+) and adaptive (Vγ9-) subsets, which have distinct functions in microbial immunosurveillance

Response of a laterally loaded 4x4 battered pile group

A lateral load test was conducted on an instrumented 4x4 fixed head battered pile group in a centrifuge. A vertical dead load of approximately 50% of the axial capacity of the pile group, which was equivalent to the design vertical load, was applied during the lateral load test. Shear forces (subgrade reaction), axial forces, and bending moments in the piles were measured and analysed. It is shown that pile-soil interaction plays an important role in sharing of lateral load between the subgrade reaction and the axial forces in the piles. The subgrade reaction takes approximately 85% of the total lateral resistance, and this percentage increases slightly with deflection. The distribution of shear forces and total lateral resistance among pile rows is not uniform; the leading row takes the largest forces, followed by the subsequent pile rows. The graphic method for analysis of battered pile groups involves incorrect basic assumptions both in the sharing of lateral loads and distribution of axial forces in the piles

Centrifuge modelling of laterally loaded single battered piles in sands

Centrifuge lateral load tests were performed on single battered piles at five pile inclinations founded in both medium-dense (relative density Dr = 55\%) and loose (Dr = 36\%) sands. The effects of pile batter and soil density on lateral resistance were studied. Pile batter had significant effects in dense sands but minor effects in loose sands. Based on the test results, nonlinear p-y curves, where p is the soil resistance in unit length and y is the lateral deflection of the pile, were developed for single piles at any angle (positive or negative) and sand density. The developed p-y curves were subsequently used with a Winkler model (COM624, LPILE, FLPIER, etc.) to predict all the test results with reasonable accuracy

A possible physical meaning of Case damping in pile dynamics

This paper presents some possible interpretations of the physical meaning of the lumped, toe, and skin Case damping factors, j(cL), j(ct), and j(cs), respectively, which are extensively utilized in the dynamic analysis of pile driveability and capacity. A single degree of freedom model is employed to relate the Case damping to the hysteretic damping ratios of soil and pile materials. This relation and the damping ratios of soils and piles show that the Case damping factors for piles in sandy and clayey soils may overlap at all strain magnitudes. Coupling of pile toe and skin resistance is analyzed, and the j(cL) factor is found to be a function of the skin and toe resistance ratio of the pile. Consequently, the j(cL) factor is an important indicator with which the skin friction and toe resistance of piles can be separated. A database of 133 cases of dynamic pile tests in Florida has been used to substantiate the analyses and interpretations. The effects of the assumptions made in this paper are also discussed

Experimental and numerical study of laterally loaded pile groups with pile caps at variable elevations

A series of lateral load tests were performed on 3 x 3 and 4 x 4 pile groups in loose and medium-dense sands in the centrifuge with their caps located at variable heights to the ground surface. Four cases were considered: Case 1, pile caps located above the ground surface; Case 2, bottom of pile cap in contact with the ground surface; Case 3, top of pile cap at the ground surface elevation; and Case 4, top of pile cap buried one cap thickness below ground surface. All tests with the exception of Case 1 of the 4 x 4 group had their pile tips located at the same elevation. A special device, which was capable of both driving the piles and raining sand on the group in flight, had to be constructed to perform the tests without stopping the centrifuge (spinning at 45 g). The tests revealed that lowering the pile cap elevation increased the lateral resistance of the pile group anywhere from 50 to 250 percent. The experimental results were subsequently modeled with the bridge foundation-superstructure finite element program FLPIER, which did a good job of predicting all the cases for different load levels without the need for soil-pile cap interaction springs (i.e., p-y springs attached to the cap). The analyses suggest that the increase in lateral resistance with lower cap elevations may be due to the lower center of rotation of the pile group. However, it should be noted that this study was for pile caps embedded in loose sand and not dense sands or at significant depths. The experiments also revealed a slight effect for the case of the pile cap embedded in sand with a footprint wider than the pile row. In that case the size of the passive soil wedge in front of the pile group, and consequently the group's lateral resistance, increased

Effects of dead loads on the lateral response of battered pile groups

The effects of vertical load on the lateral resistance of single piles were initially reviewed to facilitate the interpretation of the test results of pile groups. Then, 18 different lateral load tests were carried out in the centrifuge on the 3 x 3 and the 4 x 4 fixed-head battered pile groups to investigate the effects of vertical load on the group lateral resistance. Vertical dead loads ranging from approximately 20 to 80\% of the vertical ultimate group capacity P-uv were applied. Based on these tests, the effects of vertical dead load on the lateral resistance of the battered pile groups are found to depend on pile arrangement, pile inclination, and soil density. The lateral resistances of the 3 x 3 pile groups do not appear to vary considerably with the vertical dead loads in the range of the vertical loads studied. For the 4 x 4 pile groups however, the lateral resistances at vertical loads of approximately 50 and 80\% P-uv may be 26-29\% and even 40\% higher than that at the 20\% P-uv dead load. It may be inferred that designs based on standard lateral load tests with small vertical dead loads would be on the safe side. Three mechanisms for vertical load effects are discussed in terms of axial tension and compression failures, influence of pile inclination, and initial subgrade reaction caused by vertical loading. Preliminary numerical analyses are also performed to simulate the responses of some of the battered pile groups

Effect of width of geosynthetic reinforcement within the granular cover on the load distribution over the tunnel lining

A realistic estimation of load distribution over the buried structures is necessary for proper analysis of tunnels, culverts and pipes/conduits. Tunnels with linings are often constructed in transportation and hydraulic engineering. For the design of tunnel lining, it is essential to know the load over the lining. Load distribution over the buried structures has been investigated scientifically during the past several decades. The method of investigation includes experimental, numerical and analytical methods. The finite-element models based on some commercial software have been developed for load analyses for design of the tunnel linings and buried structures. The geosynthetic is an effective reinforcement layer to reduce the load over the buried structure. Although some studies have indicated that the geosynthetic layer can reduce the load over the buried structure, but no attempt has been made to determine the optimal width of the geosynthetic reinforcement within the granular cover. Therefore, in this paper, an attempt is made to present effect of width of geosynthetic layer on the load distribution over the tunnel lining. The study has been carried out by developing a numerical model of the problem. The commercial software PLAXIS 2D has been used for numerical modelling. The results have been presented in the form of design charts, mentioning the optimum width of geosynthetic layer, so that they can be used by practising engineers