The development of compaction bands in saturated soils, which is coupling-rate, inertial and pore-pressure-dependent, under axisymmetric loading was discussed, using a simple model and a matching technique at the movi...The development of compaction bands in saturated soils, which is coupling-rate, inertial and pore-pressure-dependent, under axisymmetric loading was discussed, using a simple model and a matching technique at the moving boundary of a band. It is shown that the development of compaction bands is dominated by the coupling-rate and pore-pressure effects of material. The soil strength makes the band shrinking, whilst pore pressure diffusion makes the band expand. Numerical simulations were carried out in this paper.展开更多
Since Mollema and Antonellini observed compaction bands in the field in 1996,different patterns of compaction bands have been found in laboratory experiments.There are some discrepancies between the laboratory experim...Since Mollema and Antonellini observed compaction bands in the field in 1996,different patterns of compaction bands have been found in laboratory experiments.There are some discrepancies between the laboratory experiments and the field observations:compared to the field observation,the stress levels required to induce compaction bands in laboratory experiments are usually higher than the inferred in the field,and the grain crushing are more intense in the laboratory experiments.In this paper,compaction bands were observed at the maximal principal stresses below 8 MPa,which is lower than the stress level inferred in the field,and there was no severe comminution inside the compaction bands.Experimental results indicate that the porosity and confining pressure have great impacts on the types of localization bands.Lower porosity and confining pressure can promote the growth of shear bands and high-angle shear bands.Higher porosity and confining pressure can promote the growth of discrete compaction bands.Intermediate porosity and confining pressure are favorable for the growth of hybrid modes involving two of the three,i.e.,discrete compaction band,diffuse compaction band and high-angle shear band.The formation of discrete compaction bands is more unstable compared to diffuse compaction bands.The two types of compaction bands can appear in the same type rocks,and diffuse compaction bands are formed under lower confining pressure compared to discrete compaction bands.The reduction of permeability was within 2 orders of magnitude in this study,and it is 2 3 orders of magnitude lower than those obtained by other researchers.展开更多
Separated transmit and receive antennas are employed to improve transmit-receive isolation in conventional short-range radars, which greatly increases the antenna size and misaligns of the transmit/receive radiation p...Separated transmit and receive antennas are employed to improve transmit-receive isolation in conventional short-range radars, which greatly increases the antenna size and misaligns of the transmit/receive radiation patterns. In this paper,a dual circularly polarized(CP) monostatic simultaneous transmit and receive(MSTAR) antenna with enhanced isolation is proposed to alleviate the problem. The proposed antenna consists of one sequentially rotating array(SRA), two beamforming networks(BFN), and a combined decoupling structure. The SRA is shared by the transmit and receive to reduce the size of the antenna and to obtain a consistent transmit and receive pattern.The BFN achieve right-hand CP for transmit and left-hand CP for receive. By exploring the combined decoupling structure of uniplanar compact electromagnetic band gap(UC-EBG) and ringshaped defected ground structure(RS-DGS), good transmitreceive isolation is achieved. The proposed antenna prototype is fabricated and experimentally characterized. The simulated and measured results show good agreement. The demonstrate transmit/receive isolation is height than 33 dB, voltage standing wave ratio is lower than 2, axial ratio is lower than 3 dB, and consistent radiation for both transmit and receive is within4.25-4.35 GHz.展开更多
文摘The development of compaction bands in saturated soils, which is coupling-rate, inertial and pore-pressure-dependent, under axisymmetric loading was discussed, using a simple model and a matching technique at the moving boundary of a band. It is shown that the development of compaction bands is dominated by the coupling-rate and pore-pressure effects of material. The soil strength makes the band shrinking, whilst pore pressure diffusion makes the band expand. Numerical simulations were carried out in this paper.
基金supported the National Natural Science Foundation of China(Grant No.51009079)National Basic Research Program of China("973" Project)(Grant Nos.2011CB013503,2013CB035902)Open Research Fund Program of State key Laboratory of Hydroscience and Engineering(Grant No.2013-KY 6)
文摘Since Mollema and Antonellini observed compaction bands in the field in 1996,different patterns of compaction bands have been found in laboratory experiments.There are some discrepancies between the laboratory experiments and the field observations:compared to the field observation,the stress levels required to induce compaction bands in laboratory experiments are usually higher than the inferred in the field,and the grain crushing are more intense in the laboratory experiments.In this paper,compaction bands were observed at the maximal principal stresses below 8 MPa,which is lower than the stress level inferred in the field,and there was no severe comminution inside the compaction bands.Experimental results indicate that the porosity and confining pressure have great impacts on the types of localization bands.Lower porosity and confining pressure can promote the growth of shear bands and high-angle shear bands.Higher porosity and confining pressure can promote the growth of discrete compaction bands.Intermediate porosity and confining pressure are favorable for the growth of hybrid modes involving two of the three,i.e.,discrete compaction band,diffuse compaction band and high-angle shear band.The formation of discrete compaction bands is more unstable compared to diffuse compaction bands.The two types of compaction bands can appear in the same type rocks,and diffuse compaction bands are formed under lower confining pressure compared to discrete compaction bands.The reduction of permeability was within 2 orders of magnitude in this study,and it is 2 3 orders of magnitude lower than those obtained by other researchers.
基金supported by Guangdong Natural Science Foundation(2019A1515011622)Guangdong Provincial Laboratory of Southern Marine Science and Engineering (Zhuhai)(SML2021SP407)。
文摘Separated transmit and receive antennas are employed to improve transmit-receive isolation in conventional short-range radars, which greatly increases the antenna size and misaligns of the transmit/receive radiation patterns. In this paper,a dual circularly polarized(CP) monostatic simultaneous transmit and receive(MSTAR) antenna with enhanced isolation is proposed to alleviate the problem. The proposed antenna consists of one sequentially rotating array(SRA), two beamforming networks(BFN), and a combined decoupling structure. The SRA is shared by the transmit and receive to reduce the size of the antenna and to obtain a consistent transmit and receive pattern.The BFN achieve right-hand CP for transmit and left-hand CP for receive. By exploring the combined decoupling structure of uniplanar compact electromagnetic band gap(UC-EBG) and ringshaped defected ground structure(RS-DGS), good transmitreceive isolation is achieved. The proposed antenna prototype is fabricated and experimentally characterized. The simulated and measured results show good agreement. The demonstrate transmit/receive isolation is height than 33 dB, voltage standing wave ratio is lower than 2, axial ratio is lower than 3 dB, and consistent radiation for both transmit and receive is within4.25-4.35 GHz.
