Influence of the penetration of adjacent X-section cast-in-place concrete(XCC)pile on the existing XCC pile in sand

A series of small-scale 1g X-section cast-in-place concrete(XCC)pile-penetration model tests were conducted to study the effects of soil density and pile geometry on the lateral responses of an existing pile and the variations in surrounding soil stress.The results showed that the bending patterns of existing XCC piles varied with penetration depth.The lateral response of the existing pile was sensitive to the change in relative density and pile geometry.For example,the bending moment of the existing pile increased along with these parameters.The development of the radial stressσ′r/σ′v0 of the soil around an existing pile showed different trends at various depths during the penetration of the adjacent pile.Moreover,the change in radial stress during the penetration of the XCC pile did not exhibit the“h/R effect”that was observed in the free-field soil,due to the shielding effect of the existing piles.The peak value of radial stressσ′r_max/σ′v0 decreased exponentially as the radial distance r/R increased.The attenuation ofσ′r_max/σ′v0 with r/R in the loose sand was faster than in the medium-dense or dense sands.Theσ′r_max/σ′v0 at the same soil location increased with the cross-section geometry parameter.

Morphology analysis of tracks in the aerogels impacted by hypervelocity irregular particles

As an attractive collector medium for hypervelocity particles,combined with outstanding physical properties and suitable compositional characteristics,SiO2 aerogel has been deployed on outer space missions and laser shock-loaded collection experiments.In this paper,impact experiments were conducted to understand the penetration process of irregular grains,irregular Al_(2)O_(3) grains with two different sizes and speeds(~110μm@7 km/s,~251μm@2.3 km/s)at various density silica aerogels.By classifying the shapes of projectile residues and tracks,the morphology of tracks was analyzed.It was observed that there were several kinds of typical tracks in the penetration of irregular grains,accompanied by residues with the shapes of near-sphere,polyhedron,streamlined body wedge,and rotator.The rotational behavior was demonstrated by the final status of one flake projectile as direct evidence.In addition,there was no obvious relationship between the track length and experimental parameters,which may be caused by the uncertain interaction between aerogels and irregular particles.In addition,it confirmed the existence of fragmentation,melting situation by observing the shape of the impact entrance hole.At the same time,optical coherence tomography was used to observe the detail of tracks clearly,which provided a method to characterize the tracks nondestructively.