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Deep Excavations with Rakers and Heel Blocks

Design deep excavation projects with internal bracing with DeepEX software!

A. Introduction:

Deep excavations are a critical component of various construction projects, ranging from building foundations to underground infrastructure. However, excavations of considerable depth present significant challenges, particularly in maintaining the stability of the surrounding soil or rock. In such scenarios, the implementation of support systems becomes essential, with rakers and heel blocks emerging as effective solutions. This article explores the concept of deep excavations with rakers and heel blocks, delving into their common uses, advantages, limitations, and how innovative software like DeepEX contributes to their design and implementation.

Deep excavation with rakers and heel blocks in Montreal - DeepEX software

Figure 1: Deep excavation with rakers and heel blocks in Montreal - Project designed with DeepEX

B. Understanding Rakers and Heel Blocks:

Rakers and heel blocks constitute a bracing system utilized to reinforce deep excavations. Rakers are diagonal braces that extend from the excavation wall to the base of the excavation. Rakers are typically connexted with heel blocks, which are horizontal support elements positioned at the excavation level. They work in conjunction with rakers to distribute loads evenly and enhance stability, thereby mitigating the risk of structural failure.

C. Common Uses:

Deep excavations with rakers and heel blocks find applications across various construction projects, where it is impractical to install tiebacks or horizontal steel struts. Typical excavation depths could be 15 to 20 ft (4.5 to 6 m), and they can reach up to 30 to 45 ft (9 to 14 m).

Rakers and heelblocks could be advantageous:

·         where excavation soils have a good bearing strength and the heel block can provide sufficient resistance (i.e. in bedrock or hard soils).

·         where tiebacks and struts cannot be installed because of adjacent structures or subway lines.

In general, rakers and heel blocks is the least favorable method for support of excavations, but there are cases that these systems are invaluable.

D. Limitations:

Despite their effectiveness, rakers and heel blocks possess certain limitations, including:

  • Design complexity: Proper design and engineering expertise are required to ensure the optimal placement and configuration of rakers and heel blocks, especially in challenging soil conditions.

  • Site-specific considerations: The suitability of rakers and heel blocks may vary depending on factors such as soil type, groundwater levels, and adjacent structures, necessitating thorough site assessment and customization.

  • Passive berm resistance: Passive soil berms are more susceptible to increased deformations, especially when excavating close to the soil friction angle.

  • Interference with permanent works: Rakers usually interfere with the permanent basement construction requiring holes and careful sequencing that can delay construction.

F. Innovative Solutions with DeepEX:

DeepEX shoring design software represents a cutting-edge solution for the design and analysis of deep excavations with rakers and heel blocks. Leveraging advanced algorithms and simulation capabilities, DeepEX enables engineers to:

·         Perform comprehensive soil-structure interaction analyses to optimize raker and heel block configurations.

·         Evaluate various design scenarios and assess the stability and safety of deep excavation projects.

·         Generate detailed reports and documentation for regulatory compliance and project communication.

The intuitive interface of the software facilitates the rapid creation of models incorporating rakers, encompassing every construction phase from berm excavation to raker and heel block activation, as well as berm soil removal. Structural section properties can be effortlessly defined using user-friendly dialogues, streamlining the design process for engineers and ensuring precise configuration of support systems.

Excavation with rakers - construction stages in DeepEX

Figure 2: Excavation with rakers - construction stages in DeepEX

DeepEX software offers extensive analysis capabilities, employing various methods such as Limit Equilibrium, Non-Linear Analysis with soil springs, and Finite Element analysis to evaluate the model comprehensively. It calculates all reactions on the rakers and heel blocks, providing engineers with crucial insights into the structural integrity of the support system. Additionally, the software conducts thorough structural and geotechnical checks on all elements, presenting detailed results both visually within the model area and in organized tables. This feature facilitates seamless review and optimization, empowering engineers to refine designs with precision and efficiency.

Deep excavation with internal rakers & kicker slab system – DeepEX software

Figure 3: Deep excavation with internal rakers & kicker slab system – DeepEX software

Model with rakers – Non-linear analysis and heel block results - DeepEX

Figure 4: Model with rakers – Non-linear analysis and heel block results - DeepEX

G. Conclusion:

Deep excavations with rakers and heel blocks play a pivotal role in ensuring the stability and success of construction projects. By understanding their applications, advantages, and limitations, alongside leveraging innovative software solutions like DeepEX, engineers can confidently design and execute deep excavation projects with enhanced efficiency and safety standards, contributing to the advancement of the construction industry.


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