Simulation take a look at examine on filling movement regulation of gangue slurry in goaf

Simulation take a look at examine on filling movement regulation of gangue slurry in goaf

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Seepage course of and traits of slurry

In accordance with the movement regulation of gangue slurry within the visible grouting take a look at column within the grouting take a look at course of (Fig. 8), it may be divided into three phases, that are interrelated and inseparable. When the gangue slurry is initially injected, the gangue slurry takes the grouting mouth because the circle middle and diffuses across the void of the simulated rock block. This stage is named the radial diffusion stage43as proven in Fig. 9a. When the gangue slurry reaches the boundary of the simulated rock void, the diffusion entrance of the slurry begins to seek out the dominant path, that’s, it permeates and diffuses to the void channel with decrease movement resistance, exhibiting an uneven axial diffusion movement attribute. This stage is named the axial diffusion stage, as proven in Fig. 9b. Within the means of axial movement diffusion of gangue slurry, when the physique weight of the slurry, the simulated self-gravity and void resistance of the higher a part of the slurry are higher than the simulated lateral resistance of the void of the slurry within the means of radial diffusion of the slurry, the slurry will movement into the encircling void and squeeze the rock block. There are each radial diffusion and axial diffusion movement traits, and this stage is named the bidirectional diffusion stage, as proven in Fig. 9c.

Determine 8
figure 8

Seepage and diffusion means of slurry.

Determine 9
figure 9

After the grouting take a look at, the combination of simulated amassed rock and gangue slurry within the take a look at column was taken out, and the slurry was evenly crammed into the void of simulated amassed rock mass to type uniform grouting plus strong, and the grouting and filling impact was good, as proven in Determine 10.

Determine 10
figure 10

Variation of slurry movement diffusion velocity

Underneath the identical grouting strain situation, the movement velocity adjustments of 76%, 78%, and 80% slurry with totally different concentrations are in contrast. The take a look at outcomes are proven in Desk 5.

Desk 5 Take a look at outcomes of slurry movement velocity change.

It may be seen from the evaluation of Fig. 11 that the movement velocity of slurry with totally different concentrations is totally different beneath the identical grouting strain, and the bigger the slurry focus, the smaller the slurry movement velocity. With the rise of grouting strain, the movement charge of slurry with totally different concentrations will increase. Taking the slurry movement velocity on the diffusion peak of 10 cm for instance, the slurry movement velocity of 76% slurry at 0.2 MPa grouting strain was 15.3 cm/s, and that at 0.3 MPa and 0.4 MPa grouting strain was 20 cm/s and 25.1 cm/s, respectively, rising by 30.72% and 64.05%. The slurry movement velocity of 78% slurry was 7.8 cm/s beneath 0.2 MPa grouting strain, and 11.07 cm/s and 15 cm/s beneath 0.3 MPa and 0.4 MPa grouting strain, rising by 41.92% and 92.31%, respectively. The slurry movement velocity of 80% focus slurry was 2.9 cm/s beneath 0.2 MPa grouting strain, and 4.2 cm/s and 5.2 cm/s beneath 0.3 MPa and 0.4 MPa grouting strain, which elevated by 44.83% and 79.31%, respectively. There’s a linear relationship between the expansion charge of slurry movement velocity of the three concentrations and the expansion charge of grouting strain, as proven in Fig. 12. Furthermore, beneath the situation of the identical strain improve, the bigger the slurry focus, the decrease the expansion charge of movement velocity.

Determine 11
figure 11

Change of slurry movement velocity beneath totally different grouting strain.

Determine 12
figure 12

Relation between grouting velocity improve and grouting strain improve.

There’s a nonlinear relationship between slurry velocity and slurry diffusion distance, which signifies that the movement of gangue slurry within the amassed rock mass is nonlinear, and slurry velocity decreases step by step with the rise of diffusion distance. It’s because the voidage of the amassed rock mass is a continuing worth. Because the slurry permeates into the voidage of the amassed rock mass, the voidage step by step decreases and the movement resistance step by step will increase, ensuing within the gradual attenuation of the slurry velocity, and the attenuation charge decreases with the rise of the diffusion distance. Underneath the situation of the identical slurry focus, the higher the grouting strain, the quicker the slurry velocity decay charge. Subsequently, within the precise engineering grouting, it’s essential to design the viscosity parameters of the slurry to regulate the grouting effectivity and implementability.

Change regulation of void strain

The 78% focus gangue slurry was chosen to check the change rule of void strain between the stacked rock blocks with the grouting time through the grouting course of beneath the three grouting pressures of 0.2 MPa, 0.3 MPa, and 0.4 MPa. The dynamic change curve of its inside strain through the grouting course of is proven in Fig. 13.

Determine 13
figure 13

Interstitial strain curve of amassed rocks.

The method of grouting take a look at begins from the underside up. Within the means of seepage and diffusion of the slurry, upward thrust will probably be generated on the simulated formation contained in the visible grouting take a look at column. Subsequently, a hard and fast gap plug internet is about on the higher finish of the take a look at column to stop the displacement and sliding of the simulated formation contained in the take a look at column. Because the slurry step by step rises, the strain sensors at totally different positions are subjected to strain from backside to high and step by step type peaks. When the slurry exceeds the place of the strain sensor, the flowing slurry produces upward extrusion strain on the amassed rock above the strain sensor, which causes the strain on the strain sensor to weaken and start to enter the strain aid stage, and the stress lowering pattern step by step turns into mild.

In accordance with the evaluation of Fig. 13a, beneath the grouting strain of 0.2MPa, the stress peak worth fashioned by strain sensor 5 is bigger than that fashioned by strain sensors 1, 2, 3, and 4. It may be seen from Fig. 13b,c that beneath the grouting strain of 0.3MPa and 0.4MPa, the utmost stress peak of the strain sensor can be generated on the high strain sensor 5. The utmost stress peaks beneath the three grouting pressures are 230.18 kPa, 271.55 kPa, and 317.84 kPa, respectively. In contrast with the three grouting pressures, with the rise of grouting strain, the slurry diffusion velocity additionally will increase, the preliminary second when the strain sensor is affected by the slurry movement strain is superior, and the rise charge of the height stress fashioned at every strain sensor is quicker. Because the slurry is step by step crammed into the amassed rock blocks, the void ratio between the rock blocks step by step decreases, ensuing within the greater the diffusion peak, the higher the seepage and diffusion resistance of the slurry, so the utmost stress peak is fashioned on the high, and the higher the grouting strain, the upper the stress peak.

As the buildup rock block is compressed by the strain of the gangue slurry, its porosity decreases, in order that the permeability turns into decrease, the movement resistance will increase, and the movement charge decreases. The diminished movement charge of the gangue slurry prevents the inner strain from rising, which in flip prevents the porosity within the simulated formation from being additional compressed. Subsequently, the noticed peak strain decreases from the underside to the highest, and the corresponding slurry velocity decreases quickly at first after which gently.

Change rule of slurry viscosity

It may be seen from the evaluation of Fig. 14 that on the identical diffusion peak, the viscosity of gangue slurry with the identical focus will increase with the rise of grouting strain, and the upper the grouting strain, the higher the change of slurry viscosity. Underneath totally different grouting pressures, slurry viscosity will increase steadily with the rise of diffusion peak. That is as a result of water absorption of the rock mass within the goaf. Within the means of simulating the movement of the rock mass within the goaf, the interplay between the rock mass and the slurry produces the seepage coupling phenomenon, ensuing within the water loss impact of the slurry44which leads to the viscosity of the slurry rising.

Determine 14
figure 14

As will be seen from Desk 6, beneath the grouting strain of 0.2 MPa, the ultimate viscosity of 76% focus slurry elevated by 15.61% in contrast with the preliminary viscosity worth, and the 78% focus slurry and 80% focus slurry elevated by 15.27% and 15.2% respectively. Underneath the grouting strain of 0.3 MPa, the ultimate viscosity of 76% focus slurry elevated by 20.77% in contrast with the preliminary viscosity, and the 78% focus slurry and 80% focus slurry elevated by 19.45% and 19.10%, respectively. Underneath 0.4MPa grouting strain, the ultimate viscosity of 76% focus slurry elevated by 24.53% in contrast with the preliminary viscosity worth, and the 78% focus slurry and 80% focus slurry elevated by 23.39% and 22.93%, respectively. It may be seen that with the rise of grouting strain, the distinction between the ultimate worth of slurry viscosity and the preliminary worth of slurry viscosity on the three concentrations of 76%, 78%, and 80% reveals an upward pattern. It reveals that the higher the grouting strain, the fuller the slurry rock coupling and the extra apparent the slurry water loss impact, leading to higher adjustments in slurry viscosity.

Desk 6 Distinction between preliminary viscosity and ultimate viscosity.

So as to additional analyze the affect of slurry focus on the change of slurry viscosity throughout diffusion, the distinction values of three sorts of viscosity had been obtained, as proven in Desk 7. As will be seen from Fig. 15, beneath the identical grouting strain, the upper the slurry focus, the higher the equal distinction. For a similar focus of slurry, the three variations (variations 1, 2, 3) elevated with the rise of the grouting strain. Underneath the three grouting pressures, the upper the slurry focus, the higher the change of the distinction worth, and the change of the distinction worth 3 on the identical peak of the slurry seepage diffusion is larger than that of the distinction worth 2. This means that when the slurry is subtle to the identical peak, the viscosity change of low-concentration slurry is smaller than that of high-concentration slurry, and the distinction in viscosity change tends to rise with the rise of diffusion peak.

Desk 7 Three viscosity variations.
Determine 15
figure 15

Three sorts of distinction values change beneath totally different grouting strain.

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