Weathered granite soils are abundant in China and used extensively as backfill materials. However, there is less systematic research on weathered granite compared with sedimentary types of soils, such as sand and clay. In this study, a series of laboratory tests was performed, including X-ray diffraction, sieving, expansion potential, compaction, California bearing ratio (CBR), and large-scale triaxial tests, to study the basic physical properties and mechanical behaviors of weathered granite soil. Results of the laboratory tests indicate that a clay content of 8% could be a good indicator to determine the compaction characteristics of weathered granitic soil with differing clay content. Thus, weathered granite soil with a clay content of approximately 8% would be advantageous to reach and maintain the compaction rate of subgrade and the stability of roads. However, the weathered granite soil with a clay content of approximately 4% had the largest mean value in the CBR tests, which was 95%. The critical confining pressure (100–200 kPa) is an indicator to determine the hardening characteristics of compacted weathered granitic soils under different pressures. The experimental results show that the samples exhibited different dilatancy characteristics under different confining pressures because the internal particles of the samples might have been compacted, dislocated, overturned, or broken and that the increase in peak deviatory stress resulting from an increase in mean stress was nonlinear because of particle breakage.

Quantificationally describing weathering process and characterizing particle breakage are important in predicting the behavior of coarse-grained soil (e.g., weathered granite). In order to comprehensively understand the mechanical properties of weathered granite and provide references for reasonable evaluation of the engineering properties of subgrade filling in mountains, a series of tests—X-ray diffraction, sieving, heavy compaction, large-scale triaxial, and field compaction tests—were carried out in this research. Based on the weathering process parameters (m and r) of in-situ granite samples at two typical sections of weathered granite mountains obtained by using previous grading equation, the mathematical model of weathering process with depth was proposed and the variation laws of weathering process with depth were described. The results show that, with an increase in burying depth of mountain profile (h) of weathered granite, the geological year’s parameter (m) decrease by power function, but the geometric progression constants (r) increase by power function. Some factors affecting the particle breakage properties of compacted weathered granite were evaluated by using relative breakage (B_r). Especially, the effect of field compaction condition (such as thickness of loose paving layer and number of vibratory rolling passes) on particle breakage was analyzed creatively. Through laboratory and field tests, it was found that particle gradation, mineral composition, compaction effect, stress level, and number of rolling passes significantly affected the particle breakage characteristics of weathered granite. Furthermore, it is worthy of attention that the weathered granite in this paper showed obvious particle breakage characteristics under weak compaction effect and at low stress levels and over-compaction could result in a decrease in the degree of compaction of a certain thickness of loose paving layer filled with weathered granite. Findings in this research can provide a theoretical basis for evaluating the physical properties and mechanical behavior of weathered granite as subgrade fillings.

A strong bearing capacity and the satisfaction of strict settlement requirements are necessary for high-rise buildings. A single-raft foundation cannot meet certain settlement requirements, in which case CFG (cement/fly ash/gravel, an emerging and sustainable construction material) piles can be used in the foundation to set up a cushion between the top of the pile and the raft slab, where the piles act as settlement reducers. The rafts of disconnected piles (DPs) exhibit complex synergetic interactions involving the raft, cushion, pile, and soil under the load of the superstructure. Multiple piles in particular lead to an increase in the number of degrees of freedom of the problem, resulting in difficulty in solving it. However, when the number of piles is very large and the structure is complex—for example, many buildings are placed on the same raft with basement structures—even if the embedded pile element is used during numerical calculations, either the method remains prone to non-convergence or the time needed for numerical calculations is too long. It is, thus, difficult to satisfy the requirement of an efficient scheme of evaluation in practice. To solve this problem, a method that uses a simulation of the integral equivalent of the CFG pile reinforcement zone is proposed in this paper. In the CFG pile reinforcement zone, the effect of the pile is reflected in the enhancement of parameters of the soil in the strengthened zone, and the reinforcement zone (including the soil and the pile) is regarded as an anisotropic elastoplastic material. As the structure of the pile is no longer needed in the model, its elimination significantly reduces the complexity of the model and improves its calculation efficiency. An example of a numerical calculation is provided to verify the viability and accuracy of the integral equivalent simulation method in comparison with the embedded pile element simulation method. Finally, the proposed method is applied to the three-dimensional numerical analysis of a scheme for the treatment of foundations of high- and low-rise buildings with basements, and its effectiveness is further verified through comparison with theoretical results.

In the course of operation, the construction industry will repeat deviations and adjustments to it equilibrium state. Understanding the development fluctuations of the construction industry is critical to the formulation of a country’s sustainable development strategy. The purpose of this paper is to investigate the development trend and fluctuation periodicity of the construction industry, particularly the deviation and characteristics of the development. In this paper, based on the H-P filtering method, the residual method for measurement of macro-economic cycle fluctuation is used to divide the periodic fluctuation of the Chinese construction industry into five rounds of economic cycles since the reform and opening up. The results are tested by a random test model and a self-correlation coefficient test model. The longitudinal time-series of data investigated in this research is the constant-price, gross output values of the construction industry in China in the period of 1980–2017 for a total of 38 years based on the national annual statistics. The results of the mathematical test show that the peak or valley of the economic cycle fluctuation of the construction industry in China reappears about every seven years or so. It shows that since the reform and opening up, the peak position of the cycle fluctuation of the Chinese construction industry began to decrease gradually, the valley level began to rise gradually, the volatility showed a downward trend, and the construction industry cycle fluctuation entered a steady and smooth process. The results of this study provide new comprehension of the development trend of construction industry and build the theoretical basis for governments and enterprises to judge the future development trends when formulating the relevant policies.