Evaluating Mechanical Properties of Earth Material During Intelligent Compaction (2020) / Chapter Skim
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From page 70... ...
70 Extraction of Mechanical Properties Introduction To extract mechanical properties in a practical manner, a robust backcalculation technique that does not require excessive processing time is needed. This chapter reports on the research team's efforts to develop procedure(s)
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From page 71... ...
Extraction of Mechanical Properties 71 GP method for symbolic regression. To arrive at the optimal predictive function using the GP approach, the inputs considered were: • The nonlinear k ′ parameters of the subgrade, ki′s; • The surface displacement, d1, measured on top of the subgrade; • The base nonlinear parameters, ki′b and layer thickness, h; and • The surface displacements, d2, recorded on top of the base layer.
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72 Evaluating Mechanical Properties of Earth Material During Intelligent Compaction Applying Equation 6-4 to the training dataset, the resulting base modulus predictions were again compared to those determined using the SSN FE model. As seen in Figure 6-2, the base modulus can be predicted favorably using the proposed equation.
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From page 73... ...
Extraction of Mechanical Properties 73 R² = 0.99 SEE = 4.58 MPa 0 50 100 150 200 250 300 0 100 200 300 A N N -P re di ct ed Su bg ra de M od ul us (M Pa ) FE-Determined Subgrade Modulus (MPa)
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From page 74... ...
74 Evaluating Mechanical Properties of Earth Material During Intelligent Compaction More detailed information regarding different levels of sophistication of the FE models used during the backcalculation process can be found in Appendix F Figure 6-3 shows the results obtained from the trained algorithms to backcalculate subgrade modulus for the proposed Scenarios 1 and 2.
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From page 75... ...
Extraction of Mechanical Properties 75 The difference between the field measurements and the extracted values can be attributed to the global adjustment factor acquired during the calibration process that was discussed in Chapter 5. The prediction can be thus improved by developing local adjustment factors for single- and two-layer systems distinctly.
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From page 76... ...
76 Evaluating Mechanical Properties of Earth Material During Intelligent Compaction the LWD modulus after conducting LWD tests at the sublots. The next section describes an evaluation of this process as used for both single-layer and two-layer systems.
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Extraction of Mechanical Properties 77 (cells 188 and 189)
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From page 78... ...
78 Evaluating Mechanical Properties of Earth Material During Intelligent Compaction The extracted base moduli compared well with the corresponding LWD base moduli as judged by the number of cases that fall within the ±25% uncertainty bounds. Retrieving Modulus Using Dynamic Drum Force (Approach 2)
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From page 79... ...
Extraction of Mechanical Properties 79 y = 0.19x R² = 0.63 0 20 40 60 80 100 150 200 250 300 Drum Force (kN)
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80 Evaluating Mechanical Properties of Earth Material During Intelligent Compaction COV of CMV, and drum force. Five sublots with COV of the CMVs less than or equal to 25% were selected for conducting LWD tests, as seen in Figure 6-11(b)
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