Experimental Study on Grouting Effect and Mechanical Properties of the Rockfill Materials Grouted with SCM

Insufficient compactness of rockfill materials may potentially cause excessive deformation of a concrete face rockfill dam (CFRD), thus resulting in cracking of the face slab and leakage of the dam body, thereby requiring reinforcement treatment. To date, there are no effective measures in strengthening rockfill materials. In this study, self-compacting mortar (SCM) was applied to the Shibaozhai CFRD in Gansu Province, China, to test the effectiveness of grouting reinforcement. Simultaneously, an indoor triaxial shear test was conducted to investigate the changes in the mechanical properties of rockfill materials before and after the grouting reinforcement. The on-site test results showed that the rockfill reached the desired porosity after grouting and grouting reinforcement enhanced the cementation degree of rockfill materials while maintaining uninterrupted drainage capacity, which met the requirements of rockfill grouting for the face rockfill dam. The results of the triaxial shear test indicated that the cohesive force of the rockfill materials rose by 3.95 times and the modulus increased by 7.24 times after grouting reinforcement，significantly enhancing the mechanical and deformation properties of the rockfill. An increase in the content of coarse particles was shown to enhance the stability of cementitious structures, which leads to a better skeleton effect and thereby raises the effectiveness of the grouting reinforcement. The rockfill materials also exhibited strain-softening characteristics following the grouting reinforcement. The research showed that grouting reinforcement technology is suitable for managing the deformation of high CFRDs or reinforcing ill rockfill dams.

Influence Factor on Dilatancy of Coarse-Grained Soil Based on Large-Scale Triaxial Test

Abstract：Using large-scale shearing device, K0 consolidated-drained triaxial test and isotropiclly consolidated-drained triaxial test under different confining pressures are performed for overburden material of ShuangJiangKou earth dam which relative density is 0.9. And meanwhile, isotropically consolidated-drained triaxial test under different confining pressures are also performed for overburden material of ShuangJiangKou earth dam which relative density is 0.8. The difference of strength and deformation between under under K0-consolidation condition and isotropic consolidation condition and between under different relative density, and the influence of confining pressure, relative density and consolidation condition on the dilatancy of coarse-grained are analyzed. The results show that the strength of K0 consolidated-drained triaxial shear test is slight greater than that obtained by isotropically consolidated-drained test. The strength of coarse-grained soil increases with increase of relative density.The volume strain value of isotropically consolidated-drained triaxial shear test is bigger than that of K00 consolidated-drained test, and the volume strain value decreases with the decreases of relative density. The dilatancy of coarse-grained soil decreases with the increase of confining pressure, and increases with the increase of static lateral pressure coefficient.

Experimental Study on the Effects of Water Content to Cement Soil

With pumice as the additive agent used in cement composite soil.In order to test the strength of the composite cement soil,the triaxial shear test were tested in the lab with different water content (10%,15%,20%,25%), different curing periods (7d,28d,60d),The results show that the strength of the composite cement soil first added,and then reduces. there is an optimum amount 15%.The pumice powder may evidently improve the mechanical properties of soft soil which has the characteristic of rich-water content.

The Comparation Study of Strength Properties for Intact Loess and Remolded Loess

At present, the research is not enough for the correlation of structure and stress-strain characters in domestic.The paper aims how the change of water content and confining pressure influence the stress-strain characters of intact loess and remolded loess by consolidated drained triaxial shear test for the Shanxi loess.The results showed that: the intact loess have structure, and the strength of intact loess is larger than remolded loess in the same condition. With the increasing of water content or confining pressure, the stress-strain of intact loess and remolded loess will tend to coincide and the impact of structure feature for loess strength will weaken.

Analysis of Influencing Factors on Intrinsic Length of Clay in Tianhe District of Guangzhou

In order to obtain the influencing factors and behavior of the intrinsic length of clay in Tianhe District of Guangzhou, different specimens are fabricated by the mixing clay and quartz sand in Tianhe District. Using the triaxial shear test results, the intrinsic lengths of different samples are determined. The results show that the liquidity index of matrix has little effect on the intrinsic length. The intrinsic length increases linearly with increasing reinforcing particle content. The larger the content is, in reinforcing particle the larger the decrease is in intrinsic length. The intrinsic length decreases with increased reinforcing particle size.

The Triaxial Shear Test of Artificially Frozen Soils in Tunnel Construction of Hong Kong

Three kinds of frozen soils were tested for artificial ground freezing (AGF) project in the tunnel construction of Stonecutters Island Sewage Treatment Works, Hong Kong. Triaxial shear test was conducted to obtain shear strength of frozen soils. From the test, Mohr circles and their envelopes were obtained. According to Mohr circles, shear strength of the three soils was gained. Comparing the three soils, we found the potential weaken layer which might cause failure in the construction. All the parameters obtained can be used in design and construction of AGF practice.

Study on Mechanical Property of Structural Damaged Expansive Soil with CT-Triaxial Shear Test

A series of CT-triaxial shear tests were conducted on expancive soil specimens under controlled suction and confining pressure as 50kPa and 100kPa. The derivative and axial stress in each stage and CT images of inner structure of specimens were obtained .The results show that the different damage location and damage degree on expansive soil samples have different effect on soil mechanical property. The deviatoric stress of smaller damage area sample is larger than of bigger damage area specimen when the damage locates at the same place. The deviatoric strain is independent of the damage degree of samples. The CT images show that with the axial strain increasing, the fissures in soil close gradually, the density of soil increases, and the deformation of samples gets larger with the increase of confining pressure.

Research on Wet-Chemical Deformation of Roadbed Built with Weathered Stone

Based on analyses on mineral composition, mechanical property and hydrology property, large-scale triaxial shear test and vibration test were used to study the effect on strength and deformation characteristic, which was caused by wet-chemical and soften of the fillings. Then trial roadbed was filled with 3 typical rocks. Modulus of resilience on the top of the roadbed was gotten via a larger-diameter (D=75 cm) plate loading test which could provide important parameter for pavement structure design. Wet-chemical deformation is researched under constant load amount to deadweight of the roadbed. Experiment results show : (1)single-axle compressive strength (>15 MPa) and modulus of resilience (E0=91.7 MPa) of 3 fillings match the requirement according to specification; (2) these 3 rocks can be used as filling in roadbed; (3) as the fillings have wet-chemical, soften, and expansion properties, the suggestion of damp-proofing and drainage works should be adopted in construction.