Revista Română de Materiale / Romanian Journal of Materials 2019, 49 (3), 379 - 387 379 DEVELOPMENT AND ENGINEERING APPLICATION OF STRONG PERMEABILITY GROUTING MATERIAL FOR WEATHERED GRANITE FORMATION CHUNQUAN DAI , YANXIA LONG, ZEJUN SHI, GUANGXUE XING, WENZENG HOU Key Laboratory of Disaster Prevention and Reduction of Civil Engineering in Shandong Province, Qingdao 266590, China College of Civil Engineering and Architecture, Shandong University of Science and Technology, Qingdao 266590, China Considering the high permeability and low strength of weathered granite in tunnelling and underground projects, this paper develops strong permeability grouting (SPG) materials with good fluidity, excellent impermeability and long durability based on the features of the weathered granite formation. The materials can repair and reinforce the weathered granite formation through permeation grouting. Besides, the author tested the basic mechanical properties of the proposed SPG materials, and applied them to a tunnelling project of Qingdao Metro. The test and application results show that the SPG materials enjoy great wettability and permeability to granite; the SPG materials can meet the requirements for grouting projects in granite formation, due to the good strength and impermeability of their concretions; the SPG slurries require easy steps and a low grouting pressure in construction. The promotion and application of the proposed SPG materials will definitely bring good economic and social benefits, owing to the huge demand for high-performance grouting materials at home and abroad. Keywords: Grouting Material; Weathered Granite; Orthogonal Test; Permeability 1. Introduction overcomes the defects of traditional materials in dealing with the engineering problems caused by In underground engineering, the construction weathered granite. Such a material will definitely team often encounters deep, thick formation of promote the development of grouting technology intensely, if not completely, weathered granite with and the construction of underground projects. a high water content. Such a formation is weak, Considering the high permeability and low unstable and very sensitive to water seepage. It is strength of weathered granite in tunnelling and prone to such geological disasters as collapse and underground projects, this paper develops strong water or mud inrush [1,2]. To prevent these permeability grouting (SPG) materials with good disasters, tunnel construction mainly relies on fluidity, excellent impermeability and long durability grouting to realize water plugging and based on the features of the weathered granite reinforcement [3-9]. So far, many effective grouting formation. The materials can repair and reinforce methods have been developed to solve the the weathered granite formation through geological problems of complex weathered granite permeation grouting. Besides, the author examined formation, including splitting-permeation grouting the mechanical properties and the engineering [10], clay grouting [11], segment grouting with application effect of the proposed SPG materials, horizontally-retracting drill rod [12], composite laying the basis for further promotion of the grouting, reinforcement and excavation [13], full- material. section curtain grouting [14] and curtain grouting dynamic treatment [15]. 2. Basic Performance Test on SPG Material The grouting material is a key determinant of the grouting effect, alongside with many other 2.1. Test materials influencing factors. The correct and rational (1) Metakaolin selection of the grouting material directly bears on The metakaolin for preparing grouting the success and economic benefit of the grouting material was produced through high-temperature project. In undergrounding engineering, the existing calcination of the kaolin powder purchased from a grouting materials mainly include cement slurry kaolin company in Gongyi, central China’s Henan [16], water glass slurry, water glass-cement slurry Province. [17], organic polymer chemical grouting material (2) Silica sol and composite slurry [18]. However, these Silica sol, a special nano-material, is a traditional grouting materials can only enhance the colloidal solution formed by uniformly dispersing grouting pressure, failing to achieve permeation amorphous SiO2 aggregates in water. The material grouting. is odourless, non-toxic and non-corrosive. In our Even if they are implemented in a composite test, the silica sol is the JN-30 type produced by manner, the grouting effect is still undesirable Qingdao Haiyang Chemical Co., Ltd. The despite the complicated operations. This calls for a performance indices of the silica sol are listed in new high-performance grouting material that Table 1. Autor corespondent/Corresponding author, E-mail: [email protected] 380 Chunquan Dai, Yanxia Long, Zejun Shi, Guangxue Xing, Wenzeng Hou / Development and engineering application of strong permeability grouting material for weathered granite formation Table 1 Performance indices of the silica sol 3 SiO2 content (%) Na2O content ≤ (%) pH Viscosity 25℃ (mpa·s) Density 25℃ (g/cm ) Mean particle size (nm) 30.0-31.0 0.30 8.5-10.0 7.0 1.19-1.21 10-20 Table 2 Factors and levels of the orthogonal test Factor Level A B C D E (silica sol dosage) (silicon powder dosage) (Quicklime dosage) (RLP dosage) (composite additive dosage) 1 30 10 5 1 1 2 40 15 10 3 4 3 50 20 15 5 7 4 60 25 20 7 10 (3) Silicon powder each purpose. The mix proportions of all Silicon powder is an ultrafine powder formed components in the orthogonal test were designed through the oxidation between the air and highly after a thorough literature review and repeated volatile SiO2 and silicon vapour, which are preparatory tests. The test covers 5 factors and 4 produced in the ore-smelting electric furnace levels according to the L16(45) orthogonal test during the smelting of silicon iron and industrial chart (Table 2). silicon. The silicon powder for our test, purchased The main performance of the grouting from Guizhou Zunyi Ferrosilicon Alloy Factory, material was tested by the orthogonal test in the consists of 90.75% SiO2, 3.62% Fe2O3, 1.87 Al2O3, following steps. 0.35% CaO, 1.32% MgO and 0.27% SO3. (1) Initial viscosity of the slurry (4) Quicklime In engineering practice, the slurry viscosity The quicklime was purchased from the usually means the relative viscosity, i.e. the market, which contains CaO, MgO, CO2 and SO3. viscosity ratio of a fluid to water at the same (5) Redispersible latex powder (RLP) temperature. In our test, the slurry viscosity was The RLP is a polymer powder obtained by spray measured by a 1006 type funnel viscometer, which drying of synthetic resin emulsion, added with a counts the time needed for 500mL slurry to flow modifier. The powder can form an emulsion after out of the viscometer (unit: s). being mixed with water. The RLP for our test was (2) Gelation time purchased from Wacker Chemie AG. The main The gelation time of the slurry was measured by content is a copolymer of vinyl acetate and an NDJ-1 type rotary viscometer. The time history ethylene. of slurry viscosity was determined before (6) Composite additive computing the gelation time. Under constant The composite additive was a light yellow temperature, the time was counted within 1min powder self-made from four kinds of surfactants. after the slurry was prepared, and the slurry (7) Water viscosity was measured regularly at pre-set Tap water was used for lab tests. On the intervals. Then, the viscosity-time curve of the construction site, the tester can use nearby tap slurry was plotted. The time corresponding to the water, clean groundwater and river water. viscosity of 100cp was defined as the initial gelation time, while that to the viscosity of 200cp 2.2. Test method was defined as the final gelation time. The performance of grouting material can be (3) Sweating rate: measured by many indices. Among them, the key, The prepared slurry was poured into a basic indices that affect the grouting effect are the 200mL measuring cylinder until reaching 80~90% initial viscosity of the slurry, the gelation time, the of the full scale. After standing for 2h, the sweating sweating rate, the permeability coefficient of the amount was recorded and divided by the total concretion, and the 28d compressive strength. To volume to yield the sweating rate. reduce the workload, only these key indices of the (4) Permeability coefficient of the grouting material were measured in the orthogonal concretion test that determines the initial mix proportion. The This coefficient was tested according to the test design is detailed as follows. Taking the requirements in the Test Code for Hydraulic metakaolin amount (fixed amount) as the Concrete (SL352-2006). benchmark, the basic properties of slurry and (5) Uniaxial compressive strength concretion were tested after adding different The uniaxial compressive strength was proportions of silica sol, silicon powder, quicklime, tested according to the Method of Testing RLP and composite additive, aiming to determine Cements: Determination of Strength (GB/T17671- the initial mix proportion of the grouting material for 1999). The non-vibration moulding was adopted. Chunquan Dai, Yanxia Long, Zejun Shi, Guangxue Xing, Wenzeng Hou / Development and engineering application of 381 strong permeability grouting material for weathered granite formation The prepared slurry was poured directly into often adopted to consolidate the rock weathering the triple test mould until reaching