Soft soil has been a major problem in the northern part of Java for the last decade, and several areas have been improved using the preloading method. In Indonesia, the improvement of soft soil using this method has already been regulated in several codes, such as SNI 8460:2017 and Geotechnical Manual series 4. However, these codes did not mention the effects of creep on post-settlement. In addition to creep, several factors influence the amount of post-settlement during the operational period, such as the thickness of the soft soil, load ratio, soil compression ratio, and the drain spacing and pattern. Larger spacing or pattern, higher compression ratio, greater secondary compression index (C_α), and increased soft soil thickness induce more post-settlement. In contrast, a higher load ratio resulted in less post-settlement. It was discovered that the load ratio of 1.20 stated in SNI 8460:2017 did not meet the requirement of a maximum yearly settlement of 20 mm as specified in Geotechnical Manual series 4. This research showed that with and without creep, the load ratio required should be in the range of 1.30 to 1.50, with an average value of 1.375. Furthermore, this study proposed a new coefficient, the load ratio coefficient (C_LR), that accounts for various factors influencing post-settlement. The proposed coefficient can be utilized along with a period of interest to estimate the post-settlement due to creep. It was also observed that the load ratio heavily affects the post-settlement.

The rigid and fixed diaphragm wall (RFD) is a novel strut-free retaining wall system. This system needs a rigid connection between diaphragm panels. However, in Indonesia, constructing the rigid connection between diaphragm wall panels is scarce. The main objective of this study is to investigate the effectiveness of the RFD system on lateral wall deflection and excavation stability considering anisotropic factors due to joints in the diaphragm wall panels. First, the soil and structure parameters of the three-dimensional finite element model were validated through a well-documented braced excavation case history, which is located in Central Jakarta. Then, the RFD system was introduced to the 3D model. Some parametric studies were also conducted by varying several parameters to understand their influence on safety factors and wall deflections. The analysis results indicate that the implementation of the RFD system yields positive outcomes in controlling lateral deformations. The length of buttress walls and the use of cap slabs significantly affect excavation deformations and safety factors, while the depth of cross walls and buttress walls has a less significant impact. The presence of joints in the diaphragm wall panels causes the wall to be anisotropic, resulting in a reduction in wall stiffness. The reduction in wall stiffness leads to an increase in lateral wall deformations and a decrease in the excavation safety factor.

This paper presents the results of the inclinometer monitoring and back analysis using three-dimensional finite elements in the scale pit deep excavations. Scale pit is a deep circular excavation construction with a depth of −27 m and a total diameter of 26 m. The soil layer above from the final excavation is dominated by a sandy soil layer. The retaining wall construction is a secant pile reinforced with waler beams at each excavation stage. The hardening soil model was used as soil constitutive model. The results of the back analysis show that the trend of wall deflection is close to the results of the inclinometer measurements. The maximum deflection that occurs in the wall is 5.1 mm. The effective cohesion c′ of cemented soil in the case is about 50 to 200 kPa, depend on the depth of cemented sand layer. N_SPT is a number of blows for a split-barrel sampler to penetrate 30 cm into the soil during standard penetration test. The soil modulus in sand soil as a result of the modeling is equivalent to 1400 N_SPT to 2000 N_SPT (unit: kPa), while for cemented sand, it is equivalent to 7000 N_SPT. This study also investigated the effect of waler beam installation and external loads on the deformations and forces that acting in the secant pile. In this case, the external load has a dominant effect in the result of wall deflections. Meanwhile, the waler beam has no significant effect for reducing the wall deflection.