There were obvious differences between a medium gravel-less perforated pipe leach fields and a small system in the treatment of demestic sewage with the change of influent quality. In small system, COD removal rate wa...There were obvious differences between a medium gravel-less perforated pipe leach fields and a small system in the treatment of demestic sewage with the change of influent quality. In small system, COD removal rate was 91%, ammonia nitrogen removal rate was 90%, total nitrogen was 58%. In medium system, COD removal rate was 86.07%, ammonia nitrogen removal rate was 45.3%, and total nitrogen was 48.2%. This paper studied on the differences. Its main reasons were as follows: differences in opening rate (perforated area account of the total area in infiltration pipe), air flow conditions, exterior environment, and wastewater distribution. Considering those problems, Solutions and applications for the development of GPPLF are given.展开更多
A set of serf-developed apparatus for foundation physical model were utilized to conduct model tests of the multi-element composite foundation with a steel pipe pile and several gravel piles. Some load-bearing charact...A set of serf-developed apparatus for foundation physical model were utilized to conduct model tests of the multi-element composite foundation with a steel pipe pile and several gravel piles. Some load-bearing characteristics of the multi-element Composite foundation, including the curves of foundation settlement, stresses of piles, pile-soil stress ratio, and load-sharing ratio of piles and soil, were obtained to study its working performances in silty sand soil. The experimental results revealed that the multi-element composite foundation with steel pipe pile and gravel pile contributed more than the gravel pile composite foundation in improving the bearing capacity of the silty fine sand.展开更多
The influence of the overlying clay on the progression of piping in the sandy gravel foundation of water-retaining structures is often neglected. In order to study this influence, an experimental investigation was con...The influence of the overlying clay on the progression of piping in the sandy gravel foundation of water-retaining structures is often neglected. In order to study this influence, an experimental investigation was conducted on a laboratory-scale model. It was discovered that the critical hydraulic gradient and the area of the piping tunnel increase when the overlying clay thickens. With a thicker clay layer, erosion of the sandy gravel below the clay layer occurs later, but, once the erosion starts, the erosion rate is very high and the average velocity of water seeping through the cross-section of the sandy gravel increases rapidly due to the low deformability of the thick clay layer. Furthermore, it was found that the progression of piping is a complicated and iterative process involving erosion of fine particles, clogging of pores, and flushing of the clogged pores. Two types of erosion have been identified in the progression of piping: one causes the tunnel to advance upstream, and the other increases the depth of the tunnel. The results show that the overlying clay is an important factor when evaluating piping in sandy gravel foundations of water-retaining structures.展开更多
文摘There were obvious differences between a medium gravel-less perforated pipe leach fields and a small system in the treatment of demestic sewage with the change of influent quality. In small system, COD removal rate was 91%, ammonia nitrogen removal rate was 90%, total nitrogen was 58%. In medium system, COD removal rate was 86.07%, ammonia nitrogen removal rate was 45.3%, and total nitrogen was 48.2%. This paper studied on the differences. Its main reasons were as follows: differences in opening rate (perforated area account of the total area in infiltration pipe), air flow conditions, exterior environment, and wastewater distribution. Considering those problems, Solutions and applications for the development of GPPLF are given.
基金The National Natural Science Foundation of China (No.50478090)
文摘A set of serf-developed apparatus for foundation physical model were utilized to conduct model tests of the multi-element composite foundation with a steel pipe pile and several gravel piles. Some load-bearing characteristics of the multi-element Composite foundation, including the curves of foundation settlement, stresses of piles, pile-soil stress ratio, and load-sharing ratio of piles and soil, were obtained to study its working performances in silty sand soil. The experimental results revealed that the multi-element composite foundation with steel pipe pile and gravel pile contributed more than the gravel pile composite foundation in improving the bearing capacity of the silty fine sand.
基金supported by the 973 Program of China(Grant No.2012CB417005)the Postgraduate Research and Innovation Plan Project in Jiangsu Province(Grant No.CXZZ13_0243)
文摘The influence of the overlying clay on the progression of piping in the sandy gravel foundation of water-retaining structures is often neglected. In order to study this influence, an experimental investigation was conducted on a laboratory-scale model. It was discovered that the critical hydraulic gradient and the area of the piping tunnel increase when the overlying clay thickens. With a thicker clay layer, erosion of the sandy gravel below the clay layer occurs later, but, once the erosion starts, the erosion rate is very high and the average velocity of water seeping through the cross-section of the sandy gravel increases rapidly due to the low deformability of the thick clay layer. Furthermore, it was found that the progression of piping is a complicated and iterative process involving erosion of fine particles, clogging of pores, and flushing of the clogged pores. Two types of erosion have been identified in the progression of piping: one causes the tunnel to advance upstream, and the other increases the depth of the tunnel. The results show that the overlying clay is an important factor when evaluating piping in sandy gravel foundations of water-retaining structures.
