土的压缩与固结英文版

1、Compressibility and Consolidation of Soil (土的压缩与固结)In this lecture, well learnDifference between consolidation (固结) and compaction (压实)One-dimensional consolidation test (固结试验)Normal and overconsolidated soils (与超固结土)，Pre-consolidation pressure (前期固结压力)，Overconsolidation ratio (超固结比)Immediate settle

2、ment (瞬时沉降)，Primary consolidation (主固结沉降)，Secondary consolidation (次固结沉降）Terzaghis one-dimensional consolidation theory(太沙基-单向固结理论)1 Compaction Vs Consolidation (压实与固结的比较)What is the difference between compaction and consolidation?压实与固结有什么的分别?2 Compaction Vs Consolidation (压实与固结的比较)空气的体积减小孔隙水的体积减小3

3、What is consolidation? (什么是固结?)Consolidation is a time-related (时间性) process of increasing the density (增加密度) of by draining some of the water out of the voids.Coarse-grained soils (粗粒土), such as sands and gravels, consolidate at a much faster rate than fine-grained soils (幼粒土) such as silts and cla

4、ys.4 The need of consolidation theory (固结理论的重要性)Tilting of Piza Tower is due to differential settlement (不平均沉降引起塔的倾斜)Two important questions for consolidation problems (两个重要问题) How much ? (沉降有多少)How long ? (时间有多久)Piza Tower, Italy5 consolidation test (单向固结试验)Consolidation is a three-dimensional (三维)

5、 process, but the direction of flow of water is primarily vertical (主要在竖向) or one-dimensional (1-D). szvz (water flow)vxvyszvz Simplify简单化6 consolidation test (单向固结试验)土样本(竖向荷载) 侧向应变为零Vertical settlement (竖向沉降)Oedometer (固结仪)Load settlement curve or 1-D compression curve (单向压缩曲线)(水缸)7 Time related co

6、nsolidation (固结与时间关系)For each load increment (每一个荷载增量)hff8Effect of stress history (应力历史)where OCR is overconsolidation ratio (超固结比), v is current effective stress (现今有效应力) and vmax is maximum past effective stress (过去最大有效应力) or pre-consolidation pressure c (前期固结压力)OCR = 1 Normally consolidated NC s

7、oil (正常固结土)OCR 1 Overconsolidated OC soil (超固结土)过去最大有效应力过去最大有效应力9Settlement (沉降)Settlement found in soil due to loading may be divided into three categories: （在土壤中沉降分为三部分）where St is total settlement (总沉降), Si is immediate settlement (瞬时沉降) elastic deformation, 弹性变形, Sc is primary consolidation (主固结

8、沉降) change of , 有效应力改变 and Ss is secondary consolidation (次固结沉降) time, 时间10immediate settlement (瞬时沉降) primary consolidation (主固结沉降)secondary consolidation (次固结沉降)11 Immediate settlement (瞬时沉降) Immediate after loading (加荷后立即发生)No volume change (体积不变) because time is too short to drain away pore-wate

9、rVertical（竖直）settlement induces lateral expansion (侧向变形) If no lateral expansion, Si = 0 （如果没有横向扩张）Similar to rubber (橡皮 )12Primary consolidation (主固结沉降)Primary consolidation is the settlement due to the gradual dissipation（耗散） of the pore water（孔隙水） from the saturated soils or gradual increase in e

10、ffective stress (有效应力的增加). It is calculated from the following two methods:e : curvee : log curvehff13The soil pore water（孔隙水） has dissipation(消散) and Effective stress after no longer increases but settlement is still growth over time. secondary consolidation(次固结沉降)141. Soil is homogeneous (均质).2. S

11、oil is fully saturated (饱和).3. Solid particles and the pore water are incompressible (土粒与水不能压缩).4. Flow of water and compression of soil are one-dimensional (单向).Strains are small (小应变).Darcys law is valid at all hydraulic gradients.Coefficient of permeability (渗透糸数) k and the coefficient of volume compre