Settlement in geotechnical engineering is determined by assessing the compression of soil layers under structural loads. This involves soil sampling and laboratory testing to evaluate the compressibility and shear strength of the soil. The primary method includes the use of consolidation tests, where a soil sample is subjected to different levels of pressure to observe compression over time. Calculations are then made using empirical formulas or numerical models to predict settlement under the expected loadings. Field observations and instrumentation, such as settlement gauges, can also provide real-time data to monitor settlement as it occurs.«3d Prediction of tunneling-induced ground movements based on a hybrid ann and empirical methods engineering with computers»
Settlement in the field can be accurately measured using precise leveling instruments, such as differential leveling, to monitor changes in elevation over time. Inclinometers can detect lateral movements, and extensometers measure vertical soil movements. Additionally, settlement plates and GPS technology provide real-time data on ground movements. These methods offer detailed insights into the extent and rate of settlement, allowing for timely interventions.«Modern advances in the field geotechnical testing investigations of pile foundations »
Soil Type | Typical Settlement Range (mm) | Compression Index (Cc) | Recompression Index (Cr) | Preconsolidation Pressure (kPa) | Time for 90% Consolidation (days) | Bulk Density (kg/m³) | Shear Strength (kPa) | Permeability (m/s) |
---|---|---|---|---|---|---|---|---|
Clay (High Plasticity) | 20 - 120 | 0.9 - 1.2 | 0.07 - 0.2 | 100 - 300 | 70 - 350 | 1600 - 1900 | 15 - 45 | 0.1x10^-9 - 0.1x10^-7 |
Clay (Low Plasticity) | 10 - 60 | 0.15 - 0.45 | 0.05 - 0.2 | 50 - 150 | 30 - 180 | 1700 - 2000 | 25 - 75 | 0.1x10^-9 - 0.1x10^-7 |
Silt | 10 - 40 | 0.05 - 0.25 | 0.02 - 0.15 | 20 - 100 | 10 - 60 | 1450 - 1800 | 10 - 30 | 0.1x10^-8 - 0.1x10^-6 |
Sandy Soil | 1 - 10 | 0.02 - 0.1 | N/A | < 55 | 2 - 30 | 1850 - 2050 | 45 - 105 | 0.1x10^-5 - 0.1x10^-3 |
Gravel | 0 - 5 | N/A | N/A | < 30 | < 15 | 2025 - 2220 | 100 - 200 | 0.1x10^-4 - 0.1x10^-2 |
Organic Soil/Peat | 60 - 250+ | 2.0 - 3.5 | 0.15 - 0.25 | 20 - 75 | 100 - 400+ | 1000 - 1500 | 1 - 20 | 0.1x10^-9 - 0.1x10^-7 |
In conclusion, determining settlement involves assessing the compression of soil layers under the weight of constructed structures. This process is critical for ensuring the stability and longevity of buildings and infrastructure. By conducting thorough soil analysis and load-bearing assessments, engineers can predict how much a building will settle over time. Techniques such as standard penetration tests (SPT), oedometer tests, and the use of settlement prediction software are essential tools in this analysis. Understanding the soil's properties, including its compressibility and shear strength, allows for accurate settlement predictions. This knowledge is vital for designing foundations that can accommodate potential settlement without compromising structural integrity.«A computational procedure for predicting the long term residual settlement of a platform induced by repeated traffic loading »
Soil settlement can be classified into three main types: immediate settlement, consolidation settlement, and secondary consolidation settlement. Immediate settlement occurs shortly after loading, primarily due to the elastic deformation of dry or saturated soils without any volume change. Consolidation settlement results from the gradual expulsion of water from the soil pores under load, leading to volume reduction. Secondary consolidation settlement occurs over a long period, even after primary consolidation has ceased, due to the soil’s viscous properties.«Application of soft computing techniques for shallow foundation reliability in geotechnical engineering »
Different rates of soil settlement are caused by variations in soil type, moisture content, load intensity, and distribution. Coarse-grained soils like sand and gravel settle quickly due to their high permeability, allowing rapid expulsion of water. In contrast, fine-grained soils like clay settle slowly because of their low permeability, delaying water expulsion. Additionally, uneven loading or variations in the soil's layering can lead to differential settlement, as can changes in moisture content over time.«Geotechnical safety issues in the cities of polar regions»
The acceptable limit for differential settlement varies depending on the structure type and its intended use. For residential buildings, a differential settlement of up to 25mm can be considered acceptable. For larger structures or those with more stringent operational requirements, such as industrial buildings or bridges, the acceptable differential settlement might be lower, often within a range of 20mm. It's crucial to design foundations to accommodate these limits to prevent structural damage.«A simplified method for predicting ground settlement profiles induced by excavation in soft clay »
To reduce clay settlement, several strategies can be employed. Preloading the soil before construction helps accelerate consolidation, allowing settlement to occur under controlled conditions. Installing vertical drains, such as sand drains or wick drains, enhances water expulsion, speeding up consolidation. Lime or cement stabilization improves the soil's strength and stiffness, reducing its compressibility. Additionally, choosing a suitable foundation type, such as deep foundations that transfer loads to more stable soil layers, can mitigate settlement issues.«Influence of stone column installation on settlement reduction»