Depth of Soil Exploration

The object of site exploration is to provide reliable, specific and detailed information about the soil and ground water condition of the site which may be required for a safe and economic design and execution of the engineering work.

Dr. B.C. Punima

通常，土壤勘探应该先进到深度，因为结构负载导致的压力增加将在结构上没有破坏性效果（如沉降和剪切失效）。换句话说，土壤没有贡献基础的深度。这个深度被称为significant depth.

Various factors affecting significant depth are as follow.

• Type of structure
• Weight of structure
• 结构的维度
• Disposition of the loaded area
• Soil profile and layer properties

以下3个拇指规则可用于了解重要的深度。

1. 它可以深度,净分辨ase in vertical pressure becomes less than10% of the initial overburden pressure.
2. 最大的深度达到了pressure bulb or isobar diagramdrawn with an intensity of pressure varying from1/5^thor 1/10^thof the surface loading intensity (i.e.0.2Qto0.1Q). (Where Q = Initial loading intensity).
3. It may be equal to宽度的一个半到两倍或较小的装载区域的横向尺寸。

Thumb Rules to Decide Depth of Soil Exploration

以下规则（表1）可用作决定土壤勘探深度以开始勘探工作的指南。

Table-1 (Thumb Rules to Predict Depth of Exploration)
Sl. No.	Type of Foundation	Depth of Exploration
1	Isolated spread footing or raft	One and a half times the width
2	Adjacent footing with clear spacing less than twice the width	一个半时间，脚的长度
3	堆和井的基础	10 to 30 meters or more, or to a depth of one and a half times the width of structure from the bearing level (toe of pile or bottom of well)
4	挡土墙	墙壁面孔的底部宽度或一个半倍的一个半倍，以较大者为准
5	Floating basement	建筑深度
6	Dams	1. One-half the bottom width of earth dams 2. Twice the height from stream bed to crest for concrete dams, for dams less than 30 m high 3. Upto bed rock, or else, though all soft, unstable and permeable strata of overburden
7	Road cuts	1. One metre where little cut or fill is required 2. In cut sections, one metre below formation level 3. In deep cuts, equal to the bottom width or depth of the cut
8	Road Fill	Two metre below ground level or equal to the height of the fill whichever is greater
9	Borrow areas	Convenience of excavation and thickness of available material

Note:可以根据现场遇到的土壤类型来修改上述值。

参考

IS: 1892 – 1979- 基础的地下调查

Soil Mechanics & Foundationsby Dr. B.C. Punima, Ashok Kumar Jain, Arun Kumar Jain