One, usepine wood pileSolve the case of foundation

Weak foundations are a common phenomenon in actual engineering projects. For some building foundations with low stacking layers and light loads or when encountering some hidden ponds, pine piles are mostly used to solve the foundation. The following is the main control of the 110kv Lushan Substation A brief introduction to the foundation solution of the chip building is given.

(1) Geological overview of the engineering project

This project is located around Lushan, with a total construction area of ​​650M2 and double-layer full-frame shear walls. The geological profile from top to bottom consists of collapsible loess, silty clay, silty gravel river pebbles, silty clay and clay. Composition. The silt clay is soft and plastic, and the silt-containing gravel river pebbles below are medium-dense, which is an ideal bearing layer. The actual burial depth of the bearing layer is about 4 meters. At that time, concrete was considered The short pile or branch base cushion method is used to solve the problem. The solution of pine piles has been clearly determined through safety engineering.

(2) Design and calculation of pine piles

When designing short wooden columns as compaction piles, press-and-hold design can be used:

s=0.95d√(1 plus e0)\/(e0-e1)

n=a\/ap

s——spacing of piles (m)

d——pile diameter (m)

e0 - the pure natural void ratio of the soil before compaction

e1 - The void ratio specified after compaction can be specified according to the design value of the required bearing capacity of the foundation and based on the design specifications for the foundation foundation, which is greater than Note 5-3 or 5-4 of Appendix 5.

n——Number of piles per m2

a——Total area of ​​compacted piles required per m2 of foundation, a=(e0-e1)\/(1 plus e0)

ap——Single pile cross-sectional area (m2)

In the design, when there is a shell layer at the end of the pile, it can be used as an end-bearing pile, and the press-and-hold calculation is as follows:

pa=ψσa-----------------(a)

pa——single pile bearing capacity

ψ——Vertical bending index, related to the soil quality between piles, generally 1 can be used

——The in-situ stress reduction index of pile raw materials, wooden columns are taken as 0.5

σ——allowable working pressure of pile raw materials, kpa

In this case, the total value of the additional ground stress and weight of the independent foundation under the column is 955kn. Layer 3 is selected as the pile end bearing layer. The allowable bearing capacity of the foundation soil is assigned a value of 130kpa after comprehensive analysis. The foundation burial depth is 1.5 meters. The basic specifications are calculated is 2.62.8m2. The bearing layer is buried shallowly, so the end-bearing pile design is selected. According to formula (a), when fir is used as the raw material and the pile diameter is 15cm, σ is 2773.4kpa

pa=10.52773.4(0.15\/2)2π=24.5kn\/root

The number of piles required per square meter is

n=950\/(2.62.924.5)=5.14 roots\/m2

Actual 5 roots\/m2

The pile base area of ​​this project is 210M2, and the number of piles required:

2105=1050 roots

The layout of the piles is in a red plum blossom shape:

After all foundation piling is completed, 20cm thick stone blocks and gravel are paved on the top of the pile wall, compacted in all directions, and then the foundation is laid.

The above is all about the pine pile construction plan. Follow this site and there will be articles to share in the future.