The Mix Ratio Study of Self-Stressed Anti-Washout Underwater Concrete Used in Nondrainage Strengthening

Self Cite

Compared with the conventional drainage strengthening techniques, the precast concrete segment assembly strengthening method (PCSAM) is regarded as a fast, more economical, and traffic-friendly underwater strengthening method for damaged bridge piers and piles, as the drainage procedure can be omitted. However, this method still has some disadvantages, such as strength loss of the filling material, debonding of the interface due to shrinkage of the filling material, poor connection effects, and poor durability of the segment sleeves. To solve these problems, the PCSAM is improved in this study by using self-stressed anti-washout concrete (SSAWC) as the filling material and by developing a lining concrete segment sleeve (LCSS) by referring to the design theory for shield lining segments. Six specimens are designed and prepared with consideration of the influential factors, such as the self-stress, thickness of the filled concrete, and concrete strength of the LCSS, then the monotonic axial compression test is carried out to investigate the improvements in the axial compression properties of the specimens. Accordingly, extended parametric analyses are performed based on the established numerical models. Finally, the calculation formula for the bearing capacity is proposed based on the analysis results. The results indicate that the SSAWC can provide initial confining compressive stress in the core region of the piers, in addition to increasing the bearing capacity and ductility of the specimens. The improved LCSS segment connection is more reliable and increases the strengthening efficiency. The influence of self-stress on the bearing capacity of the specimens is cubic and the influence of the filled concrete strength on the bearing capacity of the specimens is nonlinear. The calculation formula for predicting the bearing capacity of axially compressed columns possesses good applicability and can be used as a reference for practical engineering.

Section: Ipcsammentioning

confidence: 99%

Section: Ipcsammentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Experimental Study on the Axial Compression Performance of an Underwater Concrete Pier Strengthened by Self-Stressed Anti-Washout Concrete and Segments

Jiang

et al. 2021

Self Cite

“…The orthogonal test method selects representative and typical test points from a large number of test points in the multi-factor optimization experiment by using the principles of mathematical statistics and orthogonality. Orthogonal tables are used to scientifically arrange and analyze the effects of multiple factors to achieve optimal test results from as few trials as possible [22,23]. In the orthogonal test, the test results are analyzed by the range analysis method and the variance analysis method.…”

Section: Principles Of the Orthogonal Testmentioning

confidence: 99%

Experimental Study on Mix Proportion Parameter Optimization of Cement Anchoring Material

Jia

Liu

2019

To prevent major deformation of surrounding rock and improve the stability of unstable rock mass, this study optimized the ratio of cement anchoring material based on the orthogonal design method and rock mechanics tests. Using the six influencing factors of coal ash content, sodium silicate content, ettringite content, naphthalene sulfonate content, water-cement ratio, and sand-cement ratio, a total of 18 sets of material matching schemes was designed. Compressive strength and pull-out force tests were carried out. The results are as follows: the compressive strength of the test piece between 43 and 55 MPa; the bond stress between the bolt and the anchoring agent range is from 103 to 136 kN; and the adhesion stress between the anchoring agent and the rock masses range is from 76 to 112 kN. The main order and degree of influence of various factors affecting the bond stress and the adhesion stress of the anchoring material were determined by range analysis and analysis of variance. The results showed that the amount of coal ash had a clear controlling effect on the bond stress, and the water-cement ratio, sand-cement ratio, and sodium silicate dosage had a significant influence on the bond stress. Moreover, the amount of sodium silicate had the greatest influence on the adhesion stress, and the water-cement ratio had the second largest influence on the adhesion stress. The amount of naphthalene sulfonate had the least influence on the adhesion stress. The above experimental data and results were subjected to multiple linear regression analyses, and the empirical equations of the mechanical indexes of the test pieces and the proportion parameters of the anchoring materials were obtained to guide the engineering support design. The engineering application showed that the optimized anchorage material could be applied to further improve the safety of the surrounding rock anchoring system. Keywords: orthogonal design method; anchoring material ratio; mechanical property index; multiple linear regression analysis; safety of anchorage system

“…High-strength concrete is often used as a high-performance building material for structures and structural elements operating in aquatic or water-saturated environments [ 1 , 2 , 3 , 4 , 5 ]. Well-known examples are dams, bridge piers, offshore platforms, quay walls, mine shaft shells in flooded soils, etc.…”

Section: Introductionmentioning

confidence: 99%

Nonlinear Mechanical Effect of Free Water on the Dynamic Compressive Strength and Fracture of High-Strength Concrete

Shilko

Konovalenko

2021

It is well-known that the effect of interstitial fluid on the fracture pattern and strength of saturated high-strength concrete is determined by qualitatively different mechanisms at quasi-static and high strain rate loading. This paper shows that the intermediate range of strain rates (10−4 s−1 < ε˙ < 100 s−1) is also characterized by the presence of a peculiar mechanism of interstitial water effect on the concrete fracture and compressive strength. Using computer simulations, we have shown that such a mechanism is the competition of two oppositely directed processes: deformation of the pore space, which leads to an increase in pore pressure; and pore fluid flow. The balance of these processes can be effectively characterized by the Darcy number, which generalizes the notion of strain rate to fluid-saturated material. We have found that the dependence of the compressive strength of high-strength concrete on the Darcy number is a decreasing sigmoid function. The parameters of this function are determined by both low-scale (capillary) and large-scale (microscopic) pore subsystems in a concrete matrix. The capillary pore network determines the phenomenon of strain-rate sensitivity of fluid-saturated concrete and logistic form of the dependence of compressive strength on strain rate. Microporosity controls the actual boundary of the quasi-static loading regime for fluid-saturated samples and determines localized fracture patterns. The results of the study are relevant to the design of special-purpose concretes, as well as the assessment of the limits of safe impacts on concrete structural elements.