Laboratory triaxial tests of the soil reinforced with roots of Manilagrass were carried out in order to understand the stress-strain relationship. The change of shear strength indexes of the soil reinforced with roots of Manilagrass was investigated with the quantity of grassroots planted in the soil specimens. The results of laboratory triaxial tests show that the strength and capacity for resisting the deformation of soil reinforced with roots are better than those of unreinforced soil. And under the certain number of grassroots layers, the strength and capacity for resisting the deformation of soil reinforced with roots increase firstly and then reduce with the increasing of Manilagrass roots quantity. In other words, there is an optimal quantity of Manilagrass roots affecting the strength and capacity for resisting the deformation of soil reinforced with roots. The research results are important for understanding the mechanism and use of vegetation protection for slope.

The long-short-piled raft foundation is an unusual type of building base. This kind of foundation is usually applied for pile foundation reinforcement of existing buildings when shortage of bearing capacity of piles occurs. The bearing capacity of pile foundation is improved and less settlement is expected. Since this method has so many obvious advantages, it is recommended in the reinforcement design of piled raft foundation of an existing building in Tianjin. Longer reinforced concrete bored piles are adopted as the supplementary ones. The bearing capacity of this kind of piled raft foundation was studied. The settlement was also analyzed with the National standard method together with the finite element numerical method. According to the study, the bearing capacity of piled raft foundation is enhanced effectively after adding piles. Also, the results show that the total settlement and differential settlement during the construction is in control respectively.

Numerical simulation is a good method for studying some academic problems in the engineering. Laboratory triaxial tests of composite soil were used widely in order to understand the stress-strain relationship. But the deformation of composite soil in laboratory triaxial tests is difficult to measure in some situation. Numerical simulation on laboratory triaxial test of composite soil with roots is carried out to see how the deformation of composite soil developed under the pressure on the specimen. Drucker-Prager constitutive model was used in the numerical simulation of finite element analysis. The results show that the numerical simulation of finite element method using Drucker-Prager constitutive model is suitable for studying the deformation development of composite soil with roots. The research results are important for understanding the deformation development of laboratory triaxial test of composite soil with roots.

Compared with pile-supported reinforced embankments, rigid-flexible pile composite foundation with geogrid reinforced cushion (RFPCFGRC) has its advantage of its economics. Piles play an important role in rigid flexible pile composite foundation with geogrid reinforced cushion. The bearing mechanics of RFPCFGRC is more complicated than that of pile-supported reinforced embankments because of addition of flexible piles. This paper discussed the diffence and the bearing mechanics of the two types of composidte foundation. The results show that addition of flexible piles has changed bearing mechanics of composite foundation and changes the load distribution among piles and soil. Soil arching degree of RFPCFGRC is larger than that of pile-supported reinforced embankments.

The self-drilling prestressed anchor is a type of ground anchor used to transmit the applied tensile load into soil or rock through cement grout. The paper outlines a general construction procedure using a special self-drilling bit. Based on the load-transfer mechanism, the construction procedure is presented for load-dispersed ground anchors. In-situ pullout tests were carried out for three self-drilling prestressed anchors of the load-dispersed compression type. The test results showed that the ultimate pullout capacity could reach 800 – 1,000 kN. After prestressing, the displacement of the anchor head was decreased by 50 % – 70 % for a low load level and 30 % – 40 % for a high load level, and the displacement induced by elastic deformation was much smaller than that induced by plastic deformation. These results demonstrate that this anchor type is suitable and economical for practical engineering needs.