Hanhua Zhu

Overview of Methods for Treating the Differential Settlement of the Soft Soil Highway Subgrade (Including the Bumps at Bridgeheads)

With the rapid construction of highways in China since the 1990s, methods for treating the differential settlement of the soft soil highway subgrade (including the bumps at bridgeheads) have gradually been developed.

Explorations of the Reasonable Structure of the Soft Soil Highway Subgrade and Solutions

The traditional “apple falling site prediction” (the apple issue) and “leaf falling site prediction” (the leaf issue) are governed by the same prediction theory. However, the actual prediction methods differ; the simplest approach is to adopt the method used by man (childhood, adulthood, and old age) for maintaining motion stability to resolve the “leaf issue”.

Analysis of Differential Settlement of Highway Soft Soil Subgrade

The soft soil subgrade has the characteristics of large pore ratio, high compressibility, high water content, low permeability, low strength, strong rheological property, strong structural property, and high sensitivity, allowing it to easily lead to differential settlement of subgrade. The core problem is the inconsistency of the designed analysis model (Fig. 1.1a) of highway soft soil subgrade and actual stress and deformation state of soft soil slag road subgrade (Fig. 1.1b, c).

Practical Design Method for the Soft Soil Highway Subgrade

The soft soil highway subgrade involves the issue of plane strain, its mechanics characteristics conform to the assumptions of the Terzaghi theory; it requires control of the stability of the state of the soft soil highway subgrade’s forced deformation; and the adoption of a synthetic method to cope with the differential settlement of the soft soil highway is necessary.

Basic Characteristics of the Soft Soil Highway Subgrade and Its Design Method

The results of structural comparison between No. 1 highway and No. 2 highway are obtained according to the studies in the previous sections, as shown in Table 7.1 and Fig. 7.1 [1, 2, 3, 4].

Practice in Treatment of the Bumps at Bridgeheads on the Highways in Wenzhou City

The highway alteration project of the section from Meilin to Shanheling in Ninghai urban areas involves a line with a total length of 11.235 km. The section is designed according to the standard for the first-class highway with 4–6 lanes; the design speed is 80 km/h; and the subgrade width is 26.5–45 m. The transportation of earthwork is restricted during highway excavation in urban areas. In addition, the outsourced fillers are also prohibited due to the difficulty in transportation. Therefore, it is more appropriate to use the undisturbed soil to carry out the construction after the undisturbed soil is treated by lime. Specific judgment can be made from an economical and environmental protection perspective, as shown in Tables 12.1 and 12.2.

Practice in Treatment of the Bumps at Bridgeheads on the Existing Highway in Taizhou City

The foam bead concrete consists of foam beads (EPS particles), medium-coarse sand, macadam, cement, and water at a certain designed mix proportion through blending. All materials used in the tests are chosen and obtained nearby. The foam beads (EPS particles) are polystyrene spherical particles with a diameter of 3–5 mm and an apparent density of 5–20 kg/m3. The cement is ordinary Portland cement PO32.5. For the aggregate, the sand fineness modulus in the fine aggregate ranges from 3.0 to 2.3. The size distribution of macadam particles in the coarse aggregate ranges from 5 to 21.5 mm. The admixtures consist of common early-strength water-reducing agents, microsilica and fly ash.

Inspirations from the Stability of Ancient Structures

India’s Jaisalmer Sandcastle is a desert castle with a history of more than 800 years. With the development of the tourism industry, many inns, hotels and entertainment venues have been built in the castle, and residents can enjoy convenient tap water.

Comparative Test, Calculation, and Analysis Concerning the Stability and Looseness of the Soft Soil Highway Subgrade

Given different subgrade structures, the loose subgrade of No. 1 highway and the stable subgrade of No. 2 highway were drilled to obtain cores. Both No. 1 highway and No. 2 highway are located within the same soft soil area and are not located far away from each other.

Comparative Test and Study of the Strength and Rheological Property of the Soft Soil Subgrade

During preparation of the samples of No. 1 and No. 2 highways’ soft soil subgrades, great effort has been made to reduce the disturbance caused to soil, to ensure that the mechanical property of indoor soil was consistent with the actual situation, as shown in Fig. (6.1) [1, 2, 3].