In-situ Stiffening and Upgrading of Ballasted Rail Track Beds via Cement Grout Injection

The goal of this project is to develop a technology for in-situ conversion of conventional ballast track beds to a hybrid concrete-ballast bed, where a rigid concrete underlayment between subgrade soil and ballast enhances the track stiffness, reduces maintenance frequencies, and accommodates higher speed and higher capacity traffic. Ballasted railroad tracks are extensively used in the United States due to their advantages of relatively low construction cost, fast water drainage, and reduction of railway noise [1]. On the other hand, they suffer from several problems, including ballast fracturing and fouling, subgrade soil intrusion, and track settlement and geometric variation. These problems have to be regularly fixed by retamping of the ballast, necessitating frequent track inspection and maintenance [2]. Additionally, ballast beds have low stiffness, which can be problematic at heavy traffic road crossings and bridge approaches, resulting in an abrupt stiffness change under rails [3]. In recent years, as demands for higher speed and higher capacity trains continue to grow, considerably higher maintenance costs and efforts for ballast track beds have been required due to high vertical and lateral forcesThe goal of this project is to develop a new technology for in-situ conversion of existing ballast track beds into hybrid ballast-concrete beds by utilizing the preplaced aggregates concrete method. The specific research objectives are: 1.To characterize the ballast interstitial void space, including its volume, void channel length/tortuosity, and permeability; 2. To use CFD modeling to determine the required rheological properties of the grout (e.g., its plastic viscosity and yield strength) to facilitate adequate void filling; 3. To design cementitious grouts to achieve the optimal rheology identified under obj. 2; 4. To perform ballast filling experiment at bench scale and to evaluate the quality of filling using NDE methods; and 5. To evaluate the track stiffness, geometric stability and load carrying capacity of hybrid concrete-ballast track through a ballast box test.