Example: Cantilever Excavation - Soil Mix Wall LEM and NL Analysis
This example presents the design of a soil mix secant pile wall (3ft soil mix piles), supporting a 10ft cantilever excavation.
The model is generated and analyzed in DeepEX software, using the classical Limit Equilibrium and the Non-Linear Analysis methods.
A. Introduction - Project Description
In this example we will design a 10ft cantilever excavation, supported by a 3ft diameter soil mix wall. The Figure below presents the project model. Tables 1 and 2 present the soil properties and the stratigraphy respectively. Table 3 presents the external loads. The general ground surface is at El. 0 ft and the general water table is at El. -15 ft.
Table 1: Soil properties.
Table 2: Stratigraphy.
Soil Layer | Elevation (ft) | OCR | Ko |
F | -0 | 1 | 0.5 |
S1 | -10 | 1 | 0.441 |
Table 3: External loads.
Load | Load Type | Start Point | End Point | Load Magnitude |
Load 1 | Strip Surcharge | (-38,0) | (-2,0) | 0.6ksf |
B. Modeling with DeepEX
B.1. Edit Soil Properties and Stratigraphy
In DeepEX we can create an unlimited number of soils and define the soil type and soil properties for each soil. The soil properties can be defined manually for each soil, or be estimated from SPT values and other test results. The following figure presents some soil properties and the project stratigraphy as defined in Tables 1 and 2.
B.2. Examined Wall Section
In DeepEX, we need to manually define the wall type and wall section to be examined in a model. The software will calculate all wall stresses and capacities according to the selected design standard and provide extensive results and check ratios for each construction stage. Based on the results, we can easily optimize the wall section, either manually, or with the use of DeepEX automatic optimization tools. In this example, we assume the use of a 3ft thick soil mix wall, which will be simulated with the unreinforced concrete secant pile wall section within DeepEX. Table 4 summarizes the examined wall section properties.
Table 4: Wall parameters.
Secant Pile Wall Width | 3 ft |
Concrete | 4 ksi |
Wall depth | 25 ft |
B.3. External Surcharge
In this model we will apply an external surcharge of 0.6 ksf, developed for 36ft, starting 2 ft behind the wall, as presented in Table 3. DeepEX will calculate the horizontal stresses that are developed on the wall, using the Elasticity Equations.
B.4. Construction Stages
In DeepEX, we can create and analyze all construction stages of a model. The construction stages both allow the more advanced analysis methods (Non-Linear – Finite Element Analysis) to converge, and can assist us with the final model optimization.
C. Limit Equilibrium and Non-Linear Analysis Results
DeepEX can perform full structural and geotechnical design of all project items (walls and supports). The calculated results (soil and water pressures, wall moment, shear and displacement diagrams, support reactions, structural and geotechnical check ratios and more) can be presented both in tables and graphically on the model area. DeepEX can analyze and present results for all construction stages, allowing the designer to review the full project history and take important decisions for the most efficient model optimization.
The following images present some typical result graphs for each analysis method.
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