Solving piling design issues with a snap!
Release time:2019-05-22
 

Driven piles

Driven piles (precast piles) are prefabricated elements (timber, steel or concrete), which are driven into the ground by percussion, pressing or vibration using proper machinery. In China, driven piles are often composed of prestressed concrete and steel pipe, while timber is also sometimes used overseas. Unlike cast-in-place concrete piles, driven piles are prefabricated in factories, which enables better quality control. The execution method used for driven piles is also faster and easier to administer.

As the demand for offshore windfarm increased in recent years, the application of steel pipe foundation has also increased. Steel pipe foundations used in offshore wind farms have high loading capacity, but it requires cumbersome equipment and a large amount of capital. Therefore, when designing and constructing steel pipe foundations, uncertainties are often kept at a minimum to prevent changes of plans or delays in construction from undermining the project at hand.
 

At the designing stage, parties would tailor the driven piles according to the geography onsite as well as the loading requirement for the superstructure. It should be noted, however, that the design of the pile is subjected to changes as needed onsite.
 

There are mainly two factors determining when to cease driving pile: pile tip elevation and degree of penetration. Pile tip elevation is determined by the position of the superstructure, while the degree of penetration of each hammering is an indicator of the pile’s load capacity. During construction, both the pile tip elevation and degree of penetration standard must be met. Alteration of construction plans is often the result of not meeting either one of the standards abovementioned, which comes at a colossal cost.

 

Simulations before the actual piling can help prevent unexpected loss by anticipating possible problems during the construction.

 

Right now, the research and development of piling simulations in China is still immature, and most of the existing software is basically just numerical analysis.

GRLWEAP Wave Equation Analysis developed by Pile Dynamic Inc. (PDI) is currently the Pile driving simulation software of choice worldwide for pile driving professionals. 

 

GRLWEAP functions

 
 
 
  • Simulates the pile response to pile driving equipment
  • Calculates driving resistance, dynamic pile stresses and estimated capacity based on field observed blow count
  • Helps select appropriate hammer and driving system with known piling, soil and capacity requirements
  • Determines pile drivability and estimates total driving time

 

GRLWEAP Graphic Outputs

 
 
 

 

01

Bearing Graph

 

The Bearing Graph depicts the relationship of capacities, pile driving stresses and stroke versus blow count. It can be used to estimate the pile bearing capacity given an observed blow count; the required blow count for a specified capacity; or the maximum capacity that a hammer-pile-soil system can achieve.

Bearing graph

 

02

Inspector’s Chart

 

The Inspector’s Chart compares stroke (or hammer energy) versus blow count for a single capacity value. Inspector’s Charts are used for diesel hammers, and external combustion hydraulic (ECH) hammers to determine, for a given bearing capacity, the required blow count versus variable hammer energy. It provides information for inspectors to determine when to cease driving the pile.

Inspector's Chart

 

03

Driveability Graph

 

The Driveability Graph is a plot of capacity, blow count and dynamic stress extrema versus depth. It allows for consideration of pile add-ons, hammer energy and efficiency changes, cushion deterioration, soil resistance degradation and soil setup during driving interruptions. The numerical summary also includes an estimate of driving time based on the calculated number of blows and on the hammer blows per minute rate. By simulating performances of different over 900 piling hammers, it can also help construction teams to choose the most economical pile hammer for their operation.

Driveability Graph
 

 

 

GRLWEAP provides 4 types of approaches to estimating penetration resistance, allowing users to tailor to their needs based on the geographical data they have.

 

1) Soil Type method

If only layers of soil and the type of soil is known, users can estimate the penetration resistance by inputting basic information regarding the property of soil. This method is only suitable for rough estimations.


 

 

2)Static analysis

Static analysis allows users to input more detailed data to more accurately estimate the characteristics of the soil.

 

3)CPT method

The CPT method allows users to input data by importing .txt files to gather information about soil’s characteristics.

 

4) API method

The API method is similar to the soil type method, but it requires users to input a completely different set of data. It is more commonly used for offshore drilling projects.

 

GRLWEAP 2010 includes drivability analysis, various stroke options for diesel hammers, soil sensitivity analysis, models for parallel or composite piles and four static analysis options. The analysis of battered (driven at an angle) piles has been enhanced in GRLWEAP 2010. When the angle is horizontal, GRLWEAP may be used to simulate the installation of culverts.

GRLWEAP’s user-friendly interface includes more than 900 preprogrammed hammers, extensive help, and numerous automatic features.

 

For more information, please contact Earth Products China Limited.
Service hotline: 400-700-9998
Email: marketing@epc.com.hk
Official website: 
en.epccn.com


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