One-dimensional consolidation of double-layered soil with non-Darcian flow described by exponent and threshold gradient

Based on non-Darcian flow law described by exponent and threshold gradient within a double-layered soil, the classic theory of one-dimensional consolidation of double-layered soil was modified to consider the change of vertical total stress with depth and time together. Because of the complexity of governing equations, the numerical solutions were obtained in detail by finite difference method. Then, the numerical solutions were compared with the analytical solutions in condition that non-Darcian flow law was degenerated to Dary’s law, and the comparison results show that numerical solutions are reliable. Finally, consolidation behavior of double-layered soil with different parameters was analyzed, and the results show that the consolidation rate of double-layered soil decreases with increasing the value of exponent and threshold of non-Darcian flow, and the exponent and threshold gradient of the first soil layer greatly influence the consolidation rate of double-layered soil. The larger the ratio of the equivalent water head of external load to the total thickness of double-layered soil, the larger the rate of the consolidation, and the similitude relationship in classical consolidation theory of double-layered soil is not satisfied. The other consolidation behavior of double-layered soil with non-Darcian flow is the same as that with Darcy’s law.     

强夯模型试验及其研究进展

简要分析了强夯模型试验设计的理论依据,讨论了强夯模型试验的相似条件,并对强夯相似准则进行了推导,提出了相似强夯模型试验和非相似强夯模型试验的概念。深入分析了强夯模型试验中严重制约强夯机理研究及工程应用的模型箱尺寸和相似比例系数选取、仪器精度及数据处理等问题,提出在模型试验中提高数据采集仪器的灵敏性和精度、建立灰色系统模型提高数据处理的精确性等建议。     

某路基堆载预压处理的有限元数值模拟

针对软弱黏土路基易发生失稳及工后沉降大的缺点,采用塑料排水板堆载预压对路基进行处理。采用等效砂墙方法及剑桥模型,建立了台州湾围海工程路基堆载预压处理的平面有限元模型。分析不同堆载高度下塑料排水板间距和长度对加载速度、预压时间和沉降值的影响。分析结果表明,预压时间受排水板长度影响明显; 预压期结束后,路面沉降均匀,可以保证路面施工质量。     

不同含水率下非饱和黄土K0固结特性试验

针对非饱和原状黄土进行了不同含水率下的恒荷重K0固结试验研究,分析了含水率对割线模量,应力应变特性及侧压力系数的影响。试验表明,在其他条件相同的情况下,割线模量随着荷载的施加逐渐减小,最终趋于稳定,达到稳定值时的割线模量随着含水率的增大而减小,且与含水率线性相关;含水率越大,静止侧压力系数K0增长速率越快,至土结构完全破坏,K0趋于稳定;不同含水率的K0值最终趋于稳定,且稳定值差异性较小;提出了考虑含水率因素的连续加载条件下K0固结过程的变形模型,为研究黄土地区K0固结过程中土体变形特性及路堤沉降提供参考。     

武汉原状粉质黏土与其重塑土的试验对比研究（I）：试验结果描述

以武汉沙湖粉质黏土为研究对象,首先借助于高压固结仪,对重塑土和原状土进行了室内侧限的固结试验;其次利用改进的应力控制式常规三轴仪,在不同的加荷路径和排水条件下,对重塑土和原状土分别进行了常规三轴试验研究,并对试验资料进行了较为系统的分析．结果表明：1）原状土的侧压力系数约为0．56,超固结比约等于1．2,为弱超固结土体,其结构屈服压力稍大于其前期固结压力;2）原状土初始的切线模量及其抗剪强度均高于重塑土相应的值;3）在固结排水条件下的三轴剪切试验,原状土的剪胀量要小于重塑土的剪胀量,但在固结不排水条件下,原状土体的剪胀趋势却明显要高于重塑土的剪胀趋势．     

碎石桩在强夯处理高饱和细粒土地基中的聚能和隔振作用

强夯法一般不适用于处理高饱和细粒土地基。但是,如果在该类地基中预先设置碎石桩,则能获得较好的处理效果。这是因为桩的聚能作用,减小了夯击能的传播损失,提高了每个夯坑的地基加固效果;桩的隔振作用,降低了夯击能对表层地基土的破坏、松动程度;桩的压重作用,减小了夯坑周围土体的隆起。碎石桩还有很好的挤土、置换等作用,从而提高了强夯法在该类地基处理中的适用性。     

Industrial Flow Designing of Dried Mud Drainage for Flush Fluid in Pingguo Aluminum

Because there are plenty of clay particles in the flush fluid of Pingguo Aluminum Mine, the consolidation technology in geotechnical engineering was adopted to carry out the disassociation of water and soil disassociation. In this method, vacuum method, electro-osmosis and chemical flocculation were used comprehensively to separate soil from flush fluid. The experiments of the method of “vacuum ＋ electro-osmosis” for drainage was made. After pretreating the flush fluid, suction pressure was offered by the sand well in the bottom and electro-osmosis was used to drain off water. The results of the experiment show that the good effect can be obtained in drainage when the electric gradient is greater than 8.3 V/cm and the quantity of sand well is more than 6. In industrial production, it is necessary to increase the quantity of sand well, to arrange the electrodes rationally and to set up an intermittent electric circuit. On the basis of the experiments, the industrial feasible flow was put forward. It may be a helpful attempt to apply consolidation technology to the fields of the environmental protection and so on.     

Estimation of Degree of Consolidation for Vacuum Preloading Projects

The degree of consolidation is usually used as one of the criteria for assessing the effectiveness of soil improvement work using the fill surcharge or vacuum preloading method. It is also often used as a design specification in a soil improvement contract. Degree of consolidation is normally calculated using settlement data. However, as the effect of vacuum preloading is controlled largely by pore water pressure changes, it is necessary to analyze the pore water pressure variations and to assess the degree of consolidation using pore water pressures. In this paper, the problems involved in the estimation of degree of consolidation using settlement data are discussed. A method to estimate the average degree of consolidation using pore water pressure data is suggested. Two case studies are presented to examine the characteristics of the pore water pressure variation of soil under vacuum loading. The degree of consolidation achieved in each of the two cases is assessed using pore water pressure data and compared with that estimated using settlement data. Factors affecting the degree of consolidation assessment are discussed.     

Impairment in long-term retention but not short-term performance on a water maze reversal task following hippocampal or mediodorsal striatal n-methyl-d-aspartate receptor blockade.

Male Long-Evans rats were injected with 32 ng/μl of the N-methyl-D-aspartate (NMDA) receptor antagonist 3-(2-carboxypiperazin-4-yl) propyl-1-phosphonic acid (CPP) or vehicle and trained to locate a hidden platform in a different location (reversal training) than used on the initial 4 days of training. Rats treated with vehicle or CPP into the dorsal hippocampus, basolateral amygdala, or mediodorsal striatum had similar latencies to locate the platform on the reversal day. Rats infused with CPP into the dorsal hippocampus or mediodorsal striatum failed to search preferentially in the novel location during a 24-hr, drug-free retention test, whereas all other groups searched preferentially in this location. Therefore, blocking dorsal hippocampal or mediodorsal striatal NMDA receptors selectively blocked long-term spatial retention without producing short-term performance deficits. (PsycINFO Database Record (c) 2010 APA, all rights reserved)