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Loess is a kind of special sediment with pore structure and rich carbonate in its composition. Due to the characteristics of structure and composition, most loess has collapsibility. There are rich loess resources distributed in the northwest area of China. With the improvement of the traffic network in the west area, the use of loess as roadbed is gradually increasing. Therefore, during the construction process, the engineering problems encountered by loess also increased, which seriously hindered the construction process of the traffic network. Most of loess in our country is collapsible loess. So the common problem in engineering is how to dispose the collapsibility of collapsible loess.In this paper, the characteristics and evaluation indexes of loess are summarized and studied, the mechanism of loess collapsibility is further explored, and the three methods of loess collapsibility treatment are summarized, which will provide guidance for future engineering problems in collapsible loess areas.

This article presents the results of theoretical studies to substantiate the optimal parameters of sand-proof structures and their influence on the amount of retained sand; to establish the nature of the distribution of air-sand flow when flowing around the roadbed of highways and the speed zone of this flow; the shapes and installation dimensions of sand-proof structures, as well as the nature of the drift of individual parts of the highway with sand. For clarity, the results are presented in the form of illustrations.

Phosphogypsum (PG) stabilized with cement can be used as a bed or base course of the road, a novel method to consume solid waste. Meanwhile, using PG filler can also generate economic benefits and social value in engineering. In this paper, mechanical tests and microscopic inspection were used to analyze the performance of PG fillers and the mechanism of the modified process. The test results indicate that 1) When the environmental pH value is 8, the PG filler can be used in roadbed filling. However, the strength of the PG filler forms slowly. Its 7d unconfined compressive strength (UCS) is only 50% of 28d UCS. 2) Sulfate (SO4 2− ) induced AFt, which may fill the meso-voids of solidified PG filler, is an essential manifestation of cement-modified PG in alkaline environments. Therefore, the solidified PG filler seems water-resistant. Once the cement clinker content (mass fraction) is more than 7%, no damage phenomenon that affects the integrity of the specimen can be detected during the 60-day soaking.

Ground-penetrating radar (GPR) is a non-destructive testing exploration technology with the advantages of high efficiency and high resolution, and is widely used in roadbed detection and disease detection. With the increasing demand for road detection, traditional handheld two-dimensional GPR detection instruments can no longer meet the normal urban road detection requirements. Therefore, new efficient vehicle-mounted three-dimensional GPR systems have emerged and been put into use. This article mainly introduces some three-dimensional GPR instruments and systems that have been put into use, analyzes their composition structure, usage characteristics, compares their similarities and differences, and data processing methods, which can provide a certain reference for the forward simulation and data processing of three-dimensional GPR.

Monitoring in highway projects is significant for the safety, efficiency and quality of construction. This paper proposes a detailed method for monitoring soft-soil roadbed and high-slope, and the layered settlement gauge and total station are employed to carry out experimental monitoring. The law and stability of soft-soil roadbed settlement and deformation under high-slope are further analyzed. The results show that the cumulative values of roadbed settlement and slope platform deformation in general both increase with the increase of monitoring time. However, near 180 days, an abnormal settlement phenomenon was monitored on both sides of the highway with a maximum value of 9.44 mm. This phenomenon was captured at gauge #1, #3, and #4 on observation stake 3, and exact oppositely, it was also observed at gauge #2 on observation stake 4. Moreover, unusual deformations of the high-slope platforms occurred over a period of 10 to 30 days, and these unusual settlements and deformations are indicative of the highway’s instability. Therefore, the monitoring on soft-soil roadbed settlement and high-slope deformation can provide reference for highway construction.

A key challenge in highway reconstruction and expansion projects is to reduce longitudinal cracking at the junction of old and new roadbeds, which is a critical issue in the maintenance of transportation infrastructure. Polymer grouting technology, a non-excavation method for hidden subgrade defects, leverages material self-expansion properties to fill voids, enhance load-bearing capacity, and bond structural layers while providing seepage control—enabling rapid repair of longitudinal pavement joints. This study investigates the seepage characteristics of polymer-grouted longitudinal joints in reconstructed pavements by simulating post-repair infiltration behavior under rainfall conditions. The results elucidate the anti-seepage efficacy of polymer grouting, offering theoretical and practical insights for efficient longitudinal joint treatment in highway expansion projects.

To reduce the environmental risks caused by the accumulation of coarse slag and enhance its comprehensive utilization efficiency, this paper takes gasification coarse slag and cement as the main research objects and explores the optimal mix ratio of coarse slag in subgrade materials. By analyzing the fundamental physical and chemical properties of coarse slag and characterizing the hydration products and microstructure of the solidified slurry, the impact of coarse slag content on the strength characteristics of coarse slag-cement-based standard test blocks was investigated. The results showed that the main chemical components of the coarse slag were SiO 2 , Al 2 O 3 , and CaO, and the loss on ignition was 16.18%, which met the suitability requirements of the cement roadbed material. As the mixing ratio of coarse slag continues to increase, the water-cement ratio with fluidity ≥180 mm gradually increases, which would hinder the hydration process of the standard specimen, reduce the generation of hydration products such as C-S-H, destroy the dense structure of the aggregate, and reduce the material strength. When the content of gasified slag was about 15% to 20%, the structure became dense, and the strength of the coarse slag-cement-based material was higher after 28 days of hydration, which was more suitable for engineering applications.

The hybrid particle-based computational platform that couples peridynamics with the discrete element method (PeriDEM) is used to model vehicle mobility over roadbeds. We consider wheels rolling over gravel beds, where gravel is allowed to deform and fracture. The motion of particles are not constrained to translation and rotation as in DEM and grains can deform elastically or inelastically. This allows for more modes of inter-particle interaction. The effects of gravel shape and topology on the vehicle mobility are examined using the higher fidelity modeling. Here we study how these aspects affect vehicle range, average vehicle velocity, traction as measured by wheel slip, as well as the overall energy needed to travel a prescribed distance. When intraparticle fracture can occur, computations identify conditions on gravel particle topology that enhance vehicle mobility. In other computer simulations it is found that the driving torque is monotonically increasing with slip and capture trends seen in experiment Smith (Journal of Terramechanics, 2014).

Super absorbent polymer (SAP) was used to improve geopolymer treatment, and the degradation law of peak strength of improved geopolymer with different dosages of SAP under dry and wet cycling effects was investigated by a digital image uniaxial test to establish the strength degradation index of SAP-improved geopolymer under dry and wet cycling. Combined with XRD, SEM, and MIP tests, the hydration products, micromorphological evolution, and pore distribution of the modified geopolymer were analyzed, and the degradation mechanism of the modified geopolymer was explored. The test results show that compared with geopolymer, the compressive strength of improved geopolymer increases significantly with the increase of SAP dosage, and the peak strength is increased by up to 62.24%. SAP could effectively improve the dry and wet durability of the improved geopolymer. The compressive strength of the improved geopolymer with 2% SAP remained more than 75% of the initial strength after 9 dry and wet cycles. Considering the effects of SAP dosage and the number of dry and wet cycles, the strength deterioration index of the SAP-improved geopolymer was proposed and verified to be accurate. The results of XRD, SEM, and MIP tests showed that the main hydration products of geopolymer are CSH, CAH, and CASH, whose cementing and filling effects enhance the adhesion and form a dense and compact structure between the particles. SAP is equivalent to the formation of a number of water reservoirs inside the geopolymer in the process of dry and wet cycling, which can fully utilize the water molecules, organize them, and control the combination of the free water inside the geopolymer and the gelling material to produce hydration products in an orderly manner, thus improving the strength of the geopolymer. Improve the strength of the geopolymer. The results provide a scientific basis for the analysis and management of roadbed damage mechanisms.

Drainage pipe leakage usually causes roadbed loosening and even collapse. Therefore it is of great significance to accurately locate and repair the leakage area. This paper studies the use of GPR to carry out the detection of drainage pipe leakage area, aiming to solve the problem of unclear electromagnetic wave field response characteristics when drainage pipes and cavities coexist. First, we used gprMax to carry out numerical simulation experiments to obtain the electromagnetic wave field response characteristics when a square cavity exists around a circular drainage pipe. Subsequently, similar data characteristics to the numerical simulation were obtained through field detection, and the area was confirmed to be a cavity caused by drainage pipe leakage through drilling. This study shows that the use of numerical simulations can provide a basis for the identification of cavities caused by drainage pipe leakage in GPR data.