Cita Sari, Undayani (2025) PENENTUAN TINGGI TIMBUNAN PRA-PEMBEBANAN PADA METODE PVD – PRA-PEMBEBANAN TERHADAP PENURUNAN KONSOLIDASI TANAH. Doctoral thesis, UNDIP.

	Text Undayani Cita Sari_21010122510002_Judul-1.pdf Download (316kB)
	Text Undayani Cita Sari_21010122510002_Bab 1.pdf Restricted to Repository staff only Download (17MB)
	Text Undayani Cita Sari_21010122510002_Bab 2.pdf Restricted to Repository staff only Download (17MB)
	Text Undayani Cita Sari_21010122510002_Bab 3.pdf Restricted to Repository staff only Download (17MB)
	Text Undayani Cita Sari_21010122510002_Bab 4.pdf Restricted to Repository staff only Download (17MB)
	Text Undayani Cita Sari_21010122510002_Bab 5.pdf Restricted to Repository staff only Download (17MB)
	Text Undayani Cita Sari_21010122510002_Bab 6.pdf Restricted to Repository staff only Download (17MB)
	Text Undayani Cita Sari_21010122510002_Daftar Pustaka.pdf Restricted to Repository staff only Download (17MB)

Abstract

The acceleration of development in Indonesia makes land use on soft soils
unavoidable. Consolidation settlement is one of the soft soil’s problems which can be
addressed, among other things, with the PVD - Preloading method. This method's design
is based on geotechnical parameter analysis, typically using the Terzaghi 1D method or
FEM. Meanwhile, the Asaoka method is used to estimate settlement using field
observation data. This method requires adjustments and engineering judgment, resulting
in uncertainty in the final results. The various methods mentioned above still have
weaknesses. Therefore, it is necessary to develop a practical method for estimating the
relationship between settlement and pre-loading embankment height. This ensures that
the planned settlement aligns with the actual results and allows for effective and efficient
implementation.
In this study, the analysis was conducted using the Terzaghi 1D empirical method,
numerical analysis using Midas GTS NX, and Asaoka predictions, which were verified
with a Settlement Plate (SP). The study was conducted on Soft Clay-Silty Clay soil, taking
a look at the Semarang-Demak toll road. Consolidation settlement analysis using
empirical and numerical methods was conducted to determine the consolidation
settlement results based on design data compared to actual settlement in the field. Based
on this, a practical method can be developed to estimate consolidation settlement. The
analysis was conducted by considering smear effect, preload embankment height, and soil
type. The Asaoka estimation method was used to analyze its suitability for the final
consolidation settlement. A new equation was proposed in this study as an empirical
method for analyzing consolidation settlement and determining the required preload
embankment height in the field.
Furthermore, an analysis using the 1D Terzaghi method was conducted to determine
the magnitude of settlement. However, settlement time calculations used the conventional
and modified Terzaghi methods. In principle, the calculation steps for both methods are
the same, but the time used is different. In the conventional Terzaghi method, the time
used is based on assumptions. Meanwhile, in the modified Terzaghi method, the time used
is based on the duration of the pre-loading embankment in the SP observations. Thus, the
magnitude of settlement in both methods is the same, while the difference lies in the
settlement time. The results of the empirical settlement analysis of the conventional
Terzaghi show differences with the SP, where the largest difference is the settlement time.
Modified Terzaghi predictions provide time conformity with observations, so this method
is more recommended, but the duration of each embankment stage must be known.
Meanwhile, back analysis showed that changes in the consolidation parameters,
compression coefficient (Cc) and recompression (Cr) resulted in a better agreement
between the time and final settlement results with a deviation of less than 1% compared
to observations. The presence of a smear zone indicated a small difference in
consolidation settlement between conditions without and with a smear zone. The
equivalent permeability coefficient (kh-equivalent), the ratio of smear radius to equivalent
drainage (rs/rw), and the ratio of smear permeability coefficient to horizontal permeability
(ks/kh) are factors that influence the analysis results. Analysis of the timing of the
embankment and leaving time stages provides more accurate results. Therefore, this
numerical method can be proposed to predict consolidation settlement.
This study found that the Asaoka method's suitability for final settlement was
98.89%, as evidenced by observations of the Settlement Plate. However, its use requires
viii
waiting for the completion of pre-loading. Furthermore, it was found that if the
consolidation settlement in the field exceeds 60%, the Asaoka method can be estimated
more accurately. This is useful for preparing for the next construction phase, even if
consolidation has not yet been completed.
The pre-loading embankment height can be determined based on the required
consolidation settlement. Therefore, the embankment height depends on the planned final
consolidation settlement of the soil. Knowing that the ratio of the current settlement to
the final settlement (ρf/δt) = 1, so that the estimated of final consolidation settlement will
be the same as designed, it requires an embankment height of 0.92% of the designed
embankment height (Ht). In this case, field settlement observations using the Settlement
Plate can be stopped at an embankment height of 92% of the planned height. This equation
is used for triangular PVD type, 0.9 m spacing, 22 m depth and Soft Clay-Silty Clay soil
type. This is advantageous because the results are not influenced by engineering judgment
and can use data from the current observation conditions, eliminating the need to wait for
final SP data to estimate settlement, as in the Asaoka method.
Furthermore, in this study, an equation relationship was obtained that can be used
to determine the pre-load embankment height and final consolidation settlement. The total
pre-load embankment height and final consolidation settlement in the field can be
estimated by the Bilinear equation relationship between the embankment height and the
current settlement with the final condition. Based on the proposed Bilinear equation, the
pre-load embankment height formula was obtained with the ratio limit ρf/δt of 0.52. This
proposed equation method is used to determine the pre-load embankment height during
the construction stage. Thus, this method can be a form of control for the implementation
of the PVD – pre-load method to obtain the planned consolidation settlement.
Keywords: height of preloading embankment, consolidation settlement, geotechnical
parameters, PVD – Preloading, FEM, smear zone

Actions (login required)

View Item