Background technology
Under field conditions (factors), cause that the reason on landslide has a lot, various factors interacts and finally causes the generation of disaster, and is wherein common by the landslide phenomenon of impervious layer initiation.Generally speaking, impervious layer all is an argillic horizon, it also is the soft interlayer in the sliding mass, this interlayer is easy to form sliding surface under gravity and phreatic effect, as Yu Dong Yunyang JiBaZi landslide before huge cunning, several meters to more than 10 meters in landslide body surface portion is thick all to be compact structure, the silty clay of water permeability extreme difference, between its time and the slide plane is the good fragmented rock body of water permeability, sliding bed is the mud stone of bad hydraulic permeability, the gliding mass trailing edge exposes fragmented rock body and has creep drawing crack seam to distribute, the infiltration of ground surface condition is good, and extra torrential rain is especially when the slabstone ditch behind the blocked and ponding Cheng Ku, surface water infiltrates in a large number, groundwater table sharply raises, and has produced powerful pore water pressure and flowing pressure, makes the safety factor of sliding mass descend 0.24~0.36.This shows that pore water is the key factor of bringing out this type of landslide.The effect of water in landslide Stability Analysis mainly comprises aspect three: the intensity parameter that makes argillic horizon of infiltrating of rainfall reduces; Reduce the normal stress of slide plane top, reduce frictional resistance, and then reduce the skid resistance of slumped mass; Flowing pressure has increased sliding force along the thrust that the side slope free face produces.Many researchers have ever made analysis to the factor of water in the sliding mass, the influence of flowing pressure to sliding mass stability has been discussed, point out when having big hydraulic slope in the sliding mass, flowing pressure is that osmotic pressure is the factor that preventing land slide must be considered, water pressure can reduce the effective stress on the sliding surface, thrust along free face can increase sliding force, and provided the design formulas of the coefficient of stability when considering flowing pressure, also adopt distinct element method to analyze the come down pressure of water of WuLong and bring out the influence on landslide.
Now people have had more understanding to water to the influence of slope stability, but can't carry out other analysis to certain factor wherein, and find out its basic law.In containing the massif of impervious layer, it is a general phenomenon that there is artesian water the below of impervious layer, people it is generally acknowledged that the softening of clay is the main cause of bringing out the landslide, when softening or softening factor is not obvious when impervious layer so, whether also can produce the landslide? as shown in Figure 1, when crack 2 infiltrations of rainwater along massif, then the water pressure of impervious layer below will raise, and along the soil layer of higher permeability to the infiltration of the downstream of sliding mass 1, formation artesian aquifer sliding mass 1 in.The water level of crevice water is relevant after the pressure of this water layer and the rainfall, if amount of precipitation is bigger, the pressure of crevice water is suitable with the weight of last overburden layer, here the effective normal stress of impervious layer will obviously reduce, thereby reduced skid resistance, and the sliding force of sliding mass 1 does not reduce, so landslide disaster has just taken place.Existing research method and device can not obtain to study artesian aquifer and bring out the required parameters in landslide, simultaneously, the research that present side slope is regularly forecast focuses mostly on the Mathematical treatment of side slope time-displacement curve, in short-period forecast or to face aspect the sliding forecast be rational, but this curve is not dull smooth, usually be irregular broken line, this makes facing of side slope sliding state be difficult to intuitively, judge easily, is taken precautions against natural calamities, mitigation brings certain difficulty.
Summary of the invention
Deficiency at the prior art existence, the water that the object of the present invention is to provide relation between a kind of critical pore water pressure, sliding mass unstability and artesian water area can be to the sliding mass unstability time etc. to study brings out the landslide simulation test device, and the present invention also provides a kind of easy judgement side slope that should go to face the domatic displacement monitoring method of sliding state further.
For achieving the above object, water of the present invention brings out the landslide simulation test device and comprises testing counter, chamber, water system and be arranged on sliding mass in the chamber, the upper surface of testing counter is horizontal by the required inclination angle, landslide of test, chamber is arranged on the testing counter, the inner chamber of chamber is divided into several independently compartments along the testing counter incline direction, these independently compartment be connected with water system independently respectively, the upper surface of chamber is provided with permeable hole, and sliding mass is argillic horizon, water barrier and sliding layer from the bottom to top.
Further, the both lateral sides of described chamber is provided with baffle plate.
Further, described water system is made up of water storage tank, inlet water tank and aqueduct, can realize the constant of intake pressure by water storage tank and inlet water tank, the valve by regulating inlet water tank or change discharging height of water level in water storage tank, the inlet water tank and can change pressure in the chamber.
Further, described water barrier is plastic sheeting or rubber film.
Further, described sliding layer is block stone layer and sand layer from the bottom to top, and wherein the sand layer extends to the sloping end of testing counter always.
Further, described testing counter is a supporting structure, and described chamber and testing counter are hinged, and the testing counter below is provided with hydraulic feed device, and chamber can be rotated around jointed shaft under the effect of hydraulic feed device, realizes the adjustment to the inclination angle, landslide.
Further, be provided with measurement mechanisms such as hydraulic pressure sensor, landslide displacement sensor in the described sliding mass.
A kind ofly judge that side slope faces the domatic displacement monitoring method of sliding state: arrange grid at slope surface, and at corresponding grid intersection place placement mark, in sloping body downslide process, kinematic parameter to mark is noted down, and determines sliding state of facing of side slope by the analysis to the mark kinematic parameter.
Further, in sloping body downslide process, with DV to the entire test track up of fixing a point, note slope deformation, displacement situation, measure the displacement of each mark afterwards by the mode of single frames capture, draw the number of each moment mark and the relation curve between the displacement at last, face sliding state by the analysis of relation curve being determined whether side slope is in.
Further, the grid of described slope surface adopts the colored pigment drafting to form.
The present invention is by custom-designed landslide experiment porch and experimental box, created the condition of artesian aquifer in landslide impervious layer and the generation sliding mass, relation between critical pore water pressure, sliding mass unstability and the artesian water area in the time of can be to the sliding mass unstability etc. is studied, thereby obtain prevention and administer the required parameters in landslide, also can judge whether side slope is in and face sliding state, simply should go by the mark that analysis is arranged on landslide surface.
The specific embodiment:
As Fig. 2, shown in Figure 3, the upper surface of testing counter 8 is horizontal by the required inclination angle, landslide of test, here be set at α, cuboid chamber 7 is arranged on the testing counter 8, chamber 7 long 1.35m, wide 1.1m, thickness 5cm, evenly be divided into 9 independently compartments along its length, compartment by the bottom right to upper left being labeled as respectively 1-9 number, each compartment has water feed apparatus and piezometer tube 17 separately, piezometer tube 17 is installed in the middle part of little compartment side, measure pressure in the casing by the height of the water column in the measuring tube 17 like this, this pressure is considered to the indoor average pressure of this septulum, it also is the average pressure of the pore water of the basement rock bottom above this chamber correspondence, the upper surface of chamber 7 is provided with uniform permeable hole, in order to seep water to argillic horizon 6, arrow is depicted as the infiltration direction among the figure, sliding mass is the argillic horizon 6 of simulating nature geologic structure from the bottom to top, water barrier 5 and sliding layer, argillic horizon 6 thickness are 2cm, water barrier 5 is plastic sheeting or rubber film, sliding layer is block stone layer 4 and sand layer 3 from the bottom to top, the thickness of sand layer and block stone layer is 10cm, wherein sand layer 3 extends to the sloping end of testing counter 8 always, form angle β with horizontal plane, in sliding mass, be provided with hydraulic pressure sensor, measurement mechanisms such as landslide displacement sensor, be convenient adjustment to the landslide inclination alpha, testing counter 8 can be designed to supporting structure, the base of chamber 7 and testing counter 8 are hinged, the below of testing counter 8 is provided with hydraulic feed device, chamber 7 can be rotated around jointed shaft under the effect of hydraulic feed device, thereby realize adjustment to the landslide inclination alpha, certainly, also can adopt derricking gear realize to the landslide inclination alpha adjustment.
The both lateral sides on chamber 18 tops is provided with baffle plate 11 and baffle plate 16, water system is made up of water storage tank 9, inlet water tank 10 and aqueduct, can realize the constant of intake pressure by water storage tank 9 and inlet water tank 10, the valve by regulating inlet water tank or change discharging heights of water level in water storage tank 9, the inlet water tank 10 and can change water pressure in the chamber 18.
As shown in Figure 2, in the research computational process of experiment, the parameter of influence stability has:
(1) geometric parameter:
The thickness t 1 of landslide inclination alpha, slope angle β, block stone layer; The thickness t 2 of sand layer;
(2) physical parameter:
Effective cohesive strength of argillic horizon and effective angle of inner friction c ', φ '; The severe γ of piece stone
1The severe γ of sand
2Pore water pressure u;
(3) fringe conditions:
There is baffle plate experimental box upper lateral both sides, can think that the friction factor f between native stone body and baffle plate remains unchanged in whole distortion, sliding process.
In process of the test, α=18 °; T1=t2=10cm; γ
1=2.65kg/cm
3γ
2=1.5kg/cm
3, test clay at every turn and all be in saturation state, so c ', φ ' is a constant in each time test; Test find when sand abundant when saturated its shear resistance very weak, so slope angle β can ignore the influence of result of the test.Since gliding mass be upper surface along chamber to lower slider, lateral pressure is less, so the frictional force of both sides also can be ignored.
According to the principle of effective stress of Tai Shaji, that the stability of sliding mass is worked is effective stress σ ', and the effective cohesive strength and the effective angle of inner friction c ' of argillic horizon, φ ', and the safety factor of the sliding mass of obtaining thus is:
In the formula, the total normal stress of σ-on sliding surface, form by the last overlying strata soil body;
σ=(γ
1t
1+γ
1t
1)cosα (2)
Pore water pressure in the u-crack;
C ' in the test, φ ', α, t1, t2, γ
1, γ
2All be definite value, so to having only that the stability of sliding mass exerts an influence
This characteristic.
For easy to operate, test is limited in 1~8 chamber compartment unit scope.In process of the test,, lower floor's clay was soaked 3-4 hour, make clay fully saturated in advance to the casing water-filling and make water pressure invariableness about the 10cm water column.Again each locellus while of chamber is progressively improved water pressure after this and test, each pressurization will wait until after the distortion of geotechnical body tends towards stability and just improve hydraulic pressure once more that the time interval between twice pressurization is no less than 20 minutes for this reason afterwards.Each change before the pressure, all will measure and record afterwards, until whole sliding mass unstability to the water pressure in the piezometer tube.Concrete experimental data is as shown in table 1.
Table 1: test statistics table during the pressurization of the whole water-filling simultaneously of chamber
The test sequence number |
The water pressure of each unit (cm water column) |
Average water pressure (cm water column) |
Each unit number |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
1 |
28 |
30 |
32 |
33 |
37 |
34 |
35 |
29 |
32.25 |
2 |
33 |
34 |
28 |
30 |
32 |
30 |
33 |
27 |
30.875 |
3 |
31.5 |
34 |
35 |
33.5 |
34 |
32 |
28.5 |
30.5 |
32.375 |
4 |
33 |
35 |
34 |
36 |
33 |
30 |
28 |
31 |
32.5 |
5 |
31 |
30 |
29 |
33 |
30 |
33 |
34 |
30 |
31.25 |
Obtain the total normal stress σ on the sliding surface and its unit be converted to the cm water column by formula (2):
Table 2: during the sliding mass unstability, the total normal stress σ relation on critical pore water pressure u and the sliding surface
The test sequence number |
1 |
2 |
3 |
4 |
5 |
Critical pore water pressure u (cm water column) |
32.25 |
30.875 |
32.375 |
32.5 |
31.25 |
Total normal stress σ on the sliding surface (cm water column) |
39.47 |
39.47 |
39.47 |
39.47 |
39.47 |
Factor of proportionality u/ σ (%) |
81.7 |
78.2 |
82.0 |
82.3 |
79.2 |
As can be seen from Table 2, about the ratio of the total stress that the pore water pressure and the last overlying strata soil body form on sliding surface reaches 80% in, unstability must take place in sliding mass.
When the crack of a large amount of rainwater along massif penetrates under the impervious layer, below impervious layer, form higher artesian aquifer, when the pressure of artesian water is suitable with the weight of last overburden layer, can determine the stability of sliding mass by the area that detects artesian water.
In this part test, earlier 9,8 two compartment cell pressure on chamber top are transferred to the 40cm water column, kept 20 minutes.Successively following cell pressure is heightened the water column to 40cm then, be about 20 minutes the blanking time in the middle of each the adjustment, until sliding.Make in the stable process of distortion keep-uping pressure, the pressure of each unit fluctuates to some extent, and we are controlled at it between 2-3cm water column.In heightening the process of pressure, hydraulic pressure has the phenomenon of downward transmission, and during to the 40cm water column, the pressure of Unit the 6th is the 14cm water column such as the 7th style.Because pressurization is to be begun by the unit of going up most, so the unstability of geotechnical body all shows as whole the slip in the test of each time.
The number of unit of pressurization when table 3 geotechnical body is unbalance
The test sequence number |
1 |
2 |
3 |
4 |
5 |
6 |
The number of unit of pressurization when taking place to slide |
6 |
4 |
4 |
3 |
3 |
3 |
When the pressure of casing reaches the 40cm water column, the geotechnical body on this casing top is in suspended state basically, promptly going up the overlying strata soil body is balanced by pore water pressure substantially at the normal stress that sliding surface forms, can see as the 30%-40% that accounts for overall area by the result of the test in the table 3 and to be in this state following time, whole sloping body can estimate the stability of side slope in view of the above comparatively easily with instability.
For judging the sliding state that faces of side slope, in the middle of test, arranged the grid of 20cm * 19cm with colored pigment (as white) at slope surface, and at the white triangle mark of corresponding grid intersection place placement, with DV to the entire test track up of fixing a point, note rising slope deformation along with pressure, the displacement situation, afterwards by the single frames capture, and measure the displacement of each mark, draw the number of each moment mark and the relation curve between the displacement at last, therefrom we can be easy and clearly find sliding state of facing of side slope, and concrete condition as shown in Figure 4.
Can be clear that the evolution process of side slope unstability from figure, the side slope of Fig. 4-1 is in original state, the displacement of all failing of all marks; Fig. 4-the 2nd, the state of side slope before unstability, mark is continuous distributed in each displaced segments; Shown in Fig. 4-3, the 4-4 is that side slope is in and faces sliding state, and the total displacement of all marks is all less, but it distributes beginning discontinuous, begun to occur the crack on this explanation side slope, whole side slope is in the hole; Side slope shown in Fig. 4-5 is slided on a large scale; Fig. 4-6 is illustrated in has new crack to produce again in the slope sliding process.So by mark is set on side slope, the displacement of periodic observation mark, particularly before and after rainfall, to strengthen the density of observation, and draw out the histogram of mark number and displacement, can make things convenient for, judge effectively the safety of side slope, find sliding state of facing of side slope comparatively exactly, thereby reduce the loss that disaster is brought.