Cemented sand gravel dam construction material

Abstract

The invention discloses a cemented sand gravel dam construction material. The construction material is used for construction of a main dam section of a cemented sand gravel dam and comprises the following components in proportion: 100 parts of water, 65 parts of cement, 65 parts of fly ash, 1670 parts of aggregate C2, 450 parts of A2 sand and 1.3 parts of a special additive, the sand ratio is 21.2%, the water-binder ratio is 0.77, the VC value is 2.0 s, and the aggregate is obtained by dividing an excavation material of a road or dam excavation waste material according to rock strength, removing impurities larger than 150 mm and processing.

Description

Technical Field

[0001] This invention belongs to the field of water conservancy engineering construction, specifically relating to a cemented gravel dam construction material. Background Technology

[0002] Cemented gravel dams are a novel type of dam structure that uses cemented gravel as the primary material, combining the economic advantages of earth-rock dams with the safety of concrete dams. Cemented gravel dam construction technology utilizes natural gravel and a small amount of cementitious materials (cement and fly ash) to prepare dam construction materials. The maximum aggregate particle size can reach 150 mm without the need for screening and washing, thus combining the adaptability of earth-rock dams with the stability of concrete dams. Furthermore, its temperature control requirements are relatively simple, and construction progress is faster, which helps to shorten the overall construction period. This dam type also exhibits strong adaptability to soft foundations and good seismic performance, maintaining stability in complex geological environments.

[0003] Given the increasingly stringent requirements for ecological and environmental protection, and the constraints on new sand and gravel mining, cemented gravel dams, with their advantages of convenient local sourcing, high construction efficiency, and environmental friendliness and energy conservation, are expected to play a more important role in the field of water conservancy and hydropower construction, bringing significant economic and environmental benefits to society. Therefore, this invention provides a cemented gravel dam construction material. Summary of the Invention

[0004] The purpose of this invention is to provide a cemented gravel dam construction material.

[0005] This invention is achieved through the following technical solution: The material mix ratio for cemented gravel dam construction described in this invention is as follows: Water 100-115 Cement 40-65 fly ash 50-65 Aggregate, special admixture 0.65-1.3 The sand ratio is 21.2-35%, the water-cement ratio is 0.77-1.15, and the VC value is 2.0-3.7s.

[0006] Preferably, the material mix ratio for the cemented gravel dam construction of the present invention is: water 100 Cement 65 fly ash 65 Aggregate, special admixture 1.3 The sand content is 21.2%, the water-cement ratio is 0.77, and the VC value is 2.0s.

[0007] The aggregate described in this invention is: A1 aggregate 1580-1590. +A2 sand 675-685 Or B1 material 1535-1540 +A2 sand 675-685 Or C2 material 1665-1675 +A2 sand 440-460 .

[0008] Preferably, the aggregate of the present invention is: C2 aggregate 1670. +A2 sand 450 .

[0009] The aggregate of this invention is derived from waste material excavated from highways or dams. The lithology is metamorphic tuff or phyllite sericite slate. The excavated material is classified into three grades (A, B, and C) according to rock strength, and impurities larger than 150mm are removed before processing. Among the A, B, and C grades, A1, B1, and C1 represent excavated material from tourist roads near the dam site, while A2, B2, and C2 represent excavated material from the dam site. The aggregate processing method is as follows: Processing of coarse aggregates: (1) Blasting and preliminary crushing: Hydraulic drilling rigs are used for drilling and blasting. The blasted stone is then processed by excavators. The blasting volume per cycle is 1200 cubic meters. Then it is transported to the processing system; (2) Crushing and screening: First, the coarse aggregate is initially crushed by a jaw crusher. Then, a vibrating screen is used to accurately screen out stones with a particle size of more than 150mm. Next, an impact crusher is used to process these large stones to ensure that the particle size reaches the standard of 5-150mm. The screened coarse aggregate is carefully classified and stored according to the particle size. (3) Primary crushing: Jaw crusher is selected with a feed opening size of 600×900mm and an adjustable discharge opening range of 65~160mm. The aggregate particle size after primary crushing shall not exceed 400mm. (4) Further crushing and screening: An impact crusher is used to process stone with a particle size greater than 150mm. The rotor speed is 650r / min, and the finished product rate is at least 90%. (5) Graded storage: The stone is divided into four grades: 5-20mm, 20-40mm, 40-80mm, and 80-150mm using a vibrating screen; Fine aggregate processing: A 400kW mobile sand making machine is used to crush 5-40mm stones in blasting waste into 0-5mm manufactured sand, with a single unit capacity of 50 tons. .

[0010] The strength of the Grade A material described in this invention is greater than 30 MPa, the strength of the Grade B material is 15-30 MPa, and the strength of the Grade C material is 5-15 MPa.

[0011] The construction material described in this invention is used for the construction of the main dam section of a cemented gravel dam.

[0012] Compared with the prior art, the present invention has the following beneficial effects: This invention fully implements the principle of adapting to local conditions in the selection of cemented gravel, employing materials of corresponding strength grades according to the different needs of the low, medium, and high stress zones of the dam body. The main raw material comes from phyllite sericite slate generated during the excavation of the dam and tourist road. Through crushing and screening processes, precise control of aggregate particle size and gradation is achieved. Simultaneously, to address the high clay content of the material source, the clay content of the gravel is strictly controlled during construction. The final cemented gravel material exhibits a 28-day compressive strength of 4.1 MPa and a 180-day strength of 11.1 MPa, demonstrating excellent compressive strength. Detailed Implementation

[0013] The technical solution of the present invention will be further described in detail below through specific embodiments.

[0014] Example 1 100 water Cement 65 fly ash 65 Aggregate C2 1670 +A2 sand 450 Special admixture 1.3 The sand content is 21.2%, the water-cement ratio is 0.77, and the VC value is 2.0s.

[0015] Example 2 Water 115 50g cement 50g fly ash Aggregate A1 1587 +A2 sand 680 Special admixture 1.0 The sand content is 29.9%, the water-cement ratio is 1.15, and the VC value is 2.2s.

[0016] Example 3 Water 115 40 cement fly ash 60 Aggregate A1 1583 +A2 Sand 678 Special admixture 1.0 The sand content is 29.9%, the water-cement ratio is 1.15, and the VC value is 3.7s.

[0017] Example 4 Water 110 40 cement fly ash 60 Aggregate B1 1537 +A2 sand 683 Special admixture 1.0 The sand content is 30.2%, the water-cement ratio is 1.1, and the VC value is 3.1s.

[0018] Example 5 Water 110 50g cement 50g fly ash Aggregate B1 1540 +A2 Sand 684 Special admixture 1.0 The sand content is 30.7%, the water-cement ratio is 1.1, and the VC value is 2.9s.

[0019] To verify the effectiveness of the invention, the inventive team conducted a series of experiments, as follows: 1. Selection and processing of sand and gravel 1.1 Selection of gravel and sand materials The natural materials for the cemented gravel dam are mainly sourced from waste materials excavated from the nearby tourist road and materials excavated from the dam itself. These materials were classified into three grades (A, B, and C) based on the rock strength calculated from point load tests. Grade A materials have a strength greater than 30 MPa, Grade B materials have a strength between 15 and 30 MPa, and Grade C materials have a strength between 5 and 15 MPa. Grades A1, B1, and C1 represent waste materials from the tourist road excavation, which are composed of relict tuff; Grades A2, B2, and C2 represent waste materials from the dam excavation, which are composed of phyllite sericite slate.

[0020] 1.2 Aggregate Processing Aggregates larger than 150mm that have been screened and rejected must undergo aggregate processing before they can be used in material mixing. Aggregate processing is crucial to ensuring the quality of the dam body, and it mainly includes two aspects: the processing of coarse aggregates and fine aggregates.

[0021] 1.2.1 Processing of coarse aggregate (1) Blasting and preliminary crushing: Hydraulic drilling rigs are used for drilling and blasting. The blasted stone is then processed by a 320-type excavator. The blasting volume per cycle is 1200 cubic meters. Then it is transported to the processing system.

[0022] (2) Crushing and Screening Process: First, the coarse aggregate is initially crushed by a jaw crusher. Then, a vibrating screen is used to precisely screen out stones with a particle size exceeding 150mm. Next, an impact crusher further processes these large stones to ensure that the particle size meets the standard of 5-150mm. The screened coarse aggregate is then carefully classified and stored according to its particle size.

[0023] (3) Initial crushing process: Jaw crusher is selected, and the aggregate particle size after initial crushing does not exceed 400mm.

[0024] (4) Further crushing and screening: Impact crusher is used to process stone with a particle size greater than 150mm. Its rotor speed is 650r / min and the finished product rate is at least 90%.

[0025] (5) Graded storage: The stone is divided into four grades: 5-20mm, 20-40mm, 40-80mm and 80-150mm by using a vibrating screen.

[0026] 1.2 Processing of fine aggregates A mobile sand making machine is used to crush 5-40mm stones in blasting waste into 0-5mm manufactured sand, with a single unit capacity of 50 tons. The fineness modulus is controlled to 2.4–2.8 by adjusting the rotor speed to meet the gradation requirements of cemented gravel.

[0027] 1.3 Control methods for mud content, gradation, and sand ratio (1) Mud content control Strictly test the mud content of sand and gravel sources, requiring a total mud content ≤5% and mud lump content ≤0.5% (if C material exceeds the standard, adjust by mixing in mud-free materials). Remove mud lumps by manual picking or mechanical screening, monitor in real time during construction, and discard or reprocess any materials exceeding the limits.

[0028] (2) Aggregate gradation optimization The content of coarse aggregate particles (5-40mm) should be controlled between 35% and 65%. If the content exceeds this limit, it should be adjusted by blending complementary graded aggregates (such as a mixture of aggregate A and aggregate B) or by mechanical crushing. To address the issue of substandard gradation in aggregate C, a combination of "strongly weathered aggregate + manufactured sand" should be used to ensure gradation continuity.

[0029] (3) Dynamic adjustment of sand ratio The designed sand ratio is 18% to 35%. In actual construction, the excess sand ratio is compensated by adding adhesives or fine aggregates.

[0030] 2. Mix proportion test 2.1 Indoor mix proportion test 2.1.1 Methods and Content Raw material testing: Physicochemical properties of dam excavation materials and highway waste materials, including mud content, apparent density, crushing index, water absorption, and alkali reactivity, are tested. Mix design: Based on the design strength C1808, the effects of cementitious material dosage, water-cement ratio, and sand ratio on mechanical properties are studied through full-gradation (450mm cube) and wet-sieve specimen (150mm cube) tests. Performance verification: Construction parameters such as compressive strength, modulus of elasticity, impermeability, interlaminar shear strength, and VC value are tested.

[0031] 2.1.2 Material property analysis (1) Mud content and physical properties Mud content: The highest mud content was found in the excavated material from the bank slope (6.2%), while the mud content of other material sources was less than 5% (meeting the specifications).

[0032] In terms of apparent density, the apparent density of coarse aggregate exceeds 2520. The C2 material has the lowest apparent density, at 2459 g / L. The apparent density of fine aggregate exceeds 2620. The apparent density of all materials exceeded the lower limit of 2450 g / L specified in the standard. .

[0033] Mechanical properties: The crushing index of highway waste is the best (7.7%), while that of weathered material from riverbank slopes is the worst (34.4%); the water absorption rate of weathered material is as high as 6.07%, significantly inferior to other material sources. Application strategy for weathered material: It is recommended to mix it with high-quality materials, especially suitable for low-strength areas in the upper part of the dam body, to ensure that the compressive strength is not less than 8MPa.

[0034] (2) Inhibition of alkaline activity Riverbed material and highway waste were identified as potentially reactive aggregates, and the occurrence of alkali-aggregate reaction was effectively curbed by incorporating 30% fly ash.

[0035] 2.1.3 Recommended mix proportions, mechanical properties, and process parameters (1) Recommended mix proportion table Table 1 Recommended Mix Proportions (2) Mechanical performance indicators Sand ratio control: The sand ratio of mix proportions 2-5 is within the recommended range of the guidelines (25%~35%). The sand ratio of mix proportion 1 is 21.1%, which is slightly lower than the recommended value of the guidelines, but the feasibility of this mix proportion has been verified by field tests.

[0036] Compressive strength: Mix ratio 1: 28d compressive strength 4.1MPa, 180d strength 11.1MPa, meets C1808.

[0037] (3) Construction process parameters VC value: Controlled between 2 and 5 seconds.

[0038] Interlayer treatment: When the paving time exceeds the allowable range, roughening treatment is required and a subbase mortar (M15) must be laid. The specific mortar mix ratio is 2:3 water. Cement 165 165 fly ash And sand 1460 .

[0039] 2.3 Results Through raw material testing, waste materials from the tourist highway (A1, B1) and excavated material from the foundation pit (A2) were selected as the main materials. The apparent density of these materials all exceeds 2470. The mud content is between 0.7% and 4.9%, and the crushing index is between 7.7% and 34.4%.

[0040] After indoor mix proportion tests and on-site process tests, mix proportion 1 (total cementitious materials 130g) was verified. The 180-day compressive strength reaches 10.9-11.8 MPa, meeting the requirements of C1808 standard.

[0041] Although the present invention has been described in detail above with general descriptions, specific embodiments, and experiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A cemented gravel dam construction material, characterized in that, The material mix ratio for the cemented gravel dam construction is as follows: Water 100-115 Cement 40-65 fly ash 50-65 Aggregate, special admixture 0.65-1.3 The sand ratio is 21.2-35%, the water-cement ratio is 0.77-1.15, and the VC value is 2.0-3.7s.

2. The cemented gravel dam construction material according to claim 1, characterized in that, The mixing ratio of the cemented gravel dam construction materials is: water 100... Cement 65 fly ash 65 Aggregate, special admixture 1.3 The sand content is 21.2%, the water-cement ratio is 0.77, and the VC value is 2.0s.

3. The cemented gravel dam construction material according to claims 1-2, characterized in that, The aggregate is: A1 aggregate 1580-1590. +A2 sand 675-685 Or B1 material 1535-1540 +A2 sand 675-685 Or C2 material 1665-1675 +A2 sand 440-460 .

4. The cemented gravel dam construction material according to claim 3, characterized in that, The aggregate is: C2 aggregate 1670. +A2 sand 450 .

5. The cemented gravel dam construction material according to claim 1, characterized in that, The aggregate is taken from the excavation waste of highways or dams, and the lithology is metamorphic tuff or phyllite sericite slate. The excavated material is divided into three grades, A, B and C, according to the rock block strength. After removing impurities larger than 150mm, it is processed to obtain the aggregate. Among the A, B and C grade materials, A1, B1 and C1 represent the excavation material of tourist highways near the dam site, and A2, B2 and C2 represent the excavation material of dams.

6. The cemented gravel dam construction material according to claim 5, characterized in that, The strength of Grade A material is greater than 30 MPa, the strength of Grade B material is 15-30 MPa, and the strength of Grade C material is 5-15 MPa.

7. The cemented gravel dam construction material according to claims 1-2, characterized in that, The construction materials are used for the construction of the main dam section of the cemented gravel dam.

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