CN101603913B - Device and method for testing permeability coefficient of cement soil - Google Patents

Abstract

The invention relates to a device and a method for testing the permeability coefficient of cement soil. The method is characterized by comprising the following steps: a, putting a sample (3) on a substrate (6), coating a thin layer of vaseline on the side wall of the sample, and covering a rubber membrane (4) on the outside of the sample; and putting permeable stones (2) at the upper part and thelower part of the soil sample; b, connecting a permeable pipe (8) with a permeation flux testing tube (8a); c, applying a pressure sigma 3 to a pressure chamber (10) by applying an ambient pressure to a water inlet pipe (9); d, applying a pressure sigma b by applying a back pressure to a water inlet pipe (7); e, reading the permeable flux of the permeation flux testing tube at an interval of delta t, and measuring water temperature T synchronously; and f, calculating the permeability coefficient of the sample according to Darcy's law. The device and the method have the following advantages: the problem of water stop on the side wall of the cement soil is solved by a flexible sealing water-stop method for adopting the rubber membrane; water head difference of permeability of the cement soil can be controlled by using back pressure, and higher water head pressure can be achieved; and when the ambient pressure is applied to the sample for water stop, the sample generates certain deformation and certain excess pore water pressure.

Description

Permeability coefficient of cement soil determinator and assay method thereof

Technical field:

The present invention relates to the assay method of geotechnological material.Be particularly related to a kind of assay method of soil cement sample infiltration coefficient.

Background technology

In recent years, the soil cement body of wall that forms of cement mixing method is widely used in foundation ditch water-stop curtain, dykes and dams and lock etc. and cuts and ooze in the engineering.The plant equipment that is to use the cement mixing pile cut-off wall stirs the soil cement non-individual body of the cement formation that adds certain volume in the stratum.From the soil cement Analysis on Mechanism, because the effect of hydrated reaction of cement and soil particle and cement-hydrate, particularly cementation and ion exchange, make the soil particle dispersion degree reduce, soil particle is further reunited, thereby hole between sealing and the filler particles, thereby undisturbed soil intensity is improved, infiltration coefficient reduces.In the engineering practical application, utilize that soil cement intensity increases, infiltration coefficient reduces this characteristics, cut at foundation ditch water-stop curtain and dike (dam), lock and ooze the very big benefit of performance in the engineering.In that water-stop curtain is oozed in the engineering seepage calculation with cutting, must provide the infiltration coefficient of soil cement.Existing permeability test, normally used osmotic coefficient investigating method is: pitch paying around the soil cement sample adds that then hydraulic pressure tests.Exist the gap because pitch shrinks between back and soil cement sample, soil cement permeability test sample sidewall sealing can't be handled and the less difficulty that waits of head difference.Retrieve widely at the problems referred to above, do not find relevant solution as yet this problem.

Summary of the invention

The object of the invention just provides a kind of mensuration permeability coefficient of cement soil proving installation and method of testing, shortcomings such as the sample sidewall sealing that exists in the prior art can't be handled, head difference is less, the test duration is long, reliability is lower, the test figure precision is low to overcome, use inconvenience.

The technical solution used in the present invention is:

A kind of permeability coefficient of cement soil determinator, it is characterized in that it comprises loam cake and base, connect a seal closure between loam cake, the base and form the pressure chamber, the loam cake middle part is provided with a pressure axis and stretches into the pressure chamber, connect a fixedly gland of soil cement sample in the pressure axis end, base one side connects a back-pressure water inlet pipe, back-pressure water inlet pipe one end feeds the base middle part and communicates with the pressure chamber, the base opposite side connects a rhizosphere and compresses into water pipe and a soakaway trench, confined pressure water inlet pipe one end communicates with the pressure chamber, and soakaway trench passes the pressure chamber and links to each other with gland.

On the basis of technique scheme, further scheme is: the base middle part is provided with the projection that cooperates with the soil cement sample, compresses into water pipe 7 one ends and feeds protruding end face and communicate with the pressure chamber.

A kind of based on above-mentioned permeability coefficient of cement soil determinator, the permeability coefficient of cement soil assay method that is produced is characterized in that:

A. the soil cement sample is installed on the base in the pressure chamber, after soil cement sample sidewall is coated with thin layer vaseline or oily matter, in soil cement sample outside cover rubber membrane; Permeable stone is all installed in soil cement sample upper and lower part, and the permeable cap in rubber membrane and base and top is tightened with bungee, makes the soil cement sample place sealed environment; After loam cake and seal closure are installed, gland 11 pushed down and fixing soil cement sample;

B. soakaway trench is connected and surveys in the osmotic flow buret, this pipe is connected atmospheric pressure;

C. give the sample ambient pressure chamber σ that exerts pressure by forcing pump and confined pressure water inlet pipe ₃, because the sample outside is with flexible rubber membrane, at σ ₃Under the stepless action of ambient water pressure, sample is closely contacted with rubber membrane carry out sealing;

D. by forcing pump and compress into water pipe and apply opposite pressure σ for soil cement sample bottom _b, this pressure is actually seepage pressure to portion's sample is provided, and with sample top soakaway trench valve open, and after being connected to survey osmotic flow buret, promptly the soil cement sample is formed head difference Δ h;

E. apply σ for the soil cement sample ₃And σ _b(σ ₃＞σ _b) after, every interval certain hour Δ t surveys and reads osmotic flow buret water seepage amount, and when the osmotic flow buret had water evenly to ooze out, the expression sample was saturated, opening entry seepage flow, measuring water temperature T in process of the test simultaneously;

F. the character of soil cement material according to the principle of darcy theorem, adopts theoretical calculation formula between discrete material and solid material $k_T=\frac{\mathrm{\ΔV}\×H\×r_w}{A\×{\mathrm{\σ}}_b\×\mathrm{\Δt}\×10},$ Calculate the infiltration coefficient of sample, in the formula: k _TThe infiltration coefficient cm/s of soil cement sample when being T ℃ for water temperature; Δ V is seepage flow cm ³H is specimen height cm; A is the long-pending cm of sample cross ²r _wDensity g/cm for water ³σ _bOpposite pressure kPa for given sample; Δ t is Seepage flow time s.

Be opposite to the ambient pressure that the rubber membrane sealing soil cement sample in the pressure chamber applies and take water pressure, its force value is neglected between soil cement intensity, perviousness and sample and rubber membrane conditional decisions such as sealing greatly.Beginning experimental stage axial force σ ₁-σ ₃Be contact stress, after ambient pressure applies, after applying opposite pressure again and making sample fully saturated, close drainpipe and opposite pressure σ _b, this moment, instrument with good conditionsi can be at σ before examination ₃The pore water pressure that soil cement under the state of saturation is measured in effect down simultaneously can calculate pore pressure parameter B _{Soil cement}Size.Before the permeability test, open drainpipe, after the sample discharging consolidation is finished, measure the sample deflection, calculate fixed back height and area respectively.Opposite pressure σ _bBe applied to the sample bottom, in order to guarantee stagnant water effect between rubber membrane and sample, soil cement is generally got σ ₃-σ _b〉=50kPa.The soakaway trench outlet inserts surveys in the pipe, measures certain time period seepage discharge.

The present invention compared with prior art has following advantage: 1. because soil cement sample sidewall is taked flexible sealing mode, be different from the conventional sample water-stopping method of prior art, make the present invention can well solve soil cement sample sidewall hermetic seal problem, this to the sample water-stopping method, exist coarse and out-of-flatness also not influence stagnant water effect to the sample outside surface; 2. by sample is applied opposite pressure, can control the head difference size of sample in real time, shorten the test required time, make it convenient, reliable and accurate; 3. this flexible water-stopping method not only is used for the soil cement permeability test, in like manner is applicable to the permeability test of discrete material to solid material, if volume of sample produces distortion, rubber membrane can not reduce stagnant water effect along with sample deformation at all.

Description of drawings:

Fig. 1 is the front view of mensuration permeability coefficient of cement soil device provided by the invention.

Embodiment

Embodiment one:

A kind of permeability coefficient of cement soil determinator, it comprises loam cake 1 and base 6, connect a seal closure 5 between loam cake 1, the base 6 and form pressure chamber 10, loam cake 1 middle part is provided with a pressure axis 12 and stretches into the pressure chamber, connect a fixedly gland 11 of soil cement sample in pressure axis 12 ends, the forcing pump 7a that a side is provided with a back-pressure water inlet pipe 7 and links to each other in the base 6, the other end of back-pressure water inlet pipe 7 feed the protruding 6a of base 6 middle parts setting and communicate with pressure chamber 10.Opposite sides are provided with a rhizosphere and compress into water pipe 9 and a soakaway trench 8 in the base 6, and confined pressure water inlet pipe 9 one ends communicate with pressure chamber 10, and soakaway trench 8 is upward through pressure chamber 10 and links to each other with gland 11 and communicate in its lower surface.

Embodiment two:

According to above-mentioned permeability coefficient of cement soil determinator, a kind of permeability coefficient of cement soil assay method of generation comprises:

A. soil cement sample 3 is installed on the base 6 in the pressure chamber, after soil cement sample sidewall was coated with thin layer vaseline or oily matter, in soil cement sample outside cover rubber membrane 4, rubber membrane 4 carried out sealing by 5 pairs of sample sidewalls of ambient pressure; Permeable stone 2 is all installed in soil cement sample upper and lower part, and the permeable cap in rubber membrane and base and top is tightened with bungee, makes the soil cement sample place sealed environment; After loam cake 1 and seal closure 5 are installed, gland 11 pushed down and fixing soil cement sample;

B. soakaway trench 8 is connected and surveys osmotic flow buret 8a bottom, this pipe sidewall is provided with scale, atmospheric pressure is connected in the upper end;

C. σ exerts pressure to give around the sample pressure chamber, road 10 by forcing pump 9a and confined pressure water inlet pipe 9 ₃, because the sample outside is with flexible rubber membrane, at σ ₃Under the stepless action of ambient water pressure, sample is closely contacted with rubber membrane carry out sealing;

D. apply opposite pressure σ for soil cement sample bottom by forcing pump 7a and back-pressure water inlet pipe 7 _b, this pressure is actually seepage pressure to portion's sample is provided, and with sample top soakaway trench valve open, and after being connected to survey osmotic flow buret, promptly the soil cement sample is formed head difference Δ h;

E. apply σ for the soil cement sample ₃And σ _b(σ ₃＞σ _b) after, every interval certain hour Δ t surveys and reads osmotic flow buret water seepage amount, and when the osmotic flow buret had water evenly to ooze out, the expression sample was saturated, opening entry seepage flow, measuring water temperature T in process of the test simultaneously;

F. the character of soil cement material according to the principle of darcy theorem, adopts theoretical calculation formula between discrete material and solid material $k_T=\frac{\mathrm{\ΔV}\×H\×r_w}{A\×{\mathrm{\σ}}_b\×\mathrm{\Δt}\×10},$ Calculate the infiltration coefficient of sample, in the formula: k _TThe infiltration coefficient cm/s of soil cement sample when being T ℃ for water temperature; Δ V is seepage flow cm ³H is specimen height cm; A is the long-pending cm of sample cross ²r _wDensity g/cm for water ³σ _bOpposite pressure kPa for given sample; Δ t is Seepage flow time s.

Claims (1)

1. permeability coefficient of cement soil assay method, adopt the osmotic coefficient investigating device, it comprises loam cake (1) and base (6), loam cake (1), connect a seal closure (5) between the base (6) and form pressure chamber (10), loam cake (1) middle part is provided with a pressure axis (12) and stretches into the pressure chamber, connect a fixedly gland of soil cement sample (11) in pressure axis (12) end, a side is provided with a back-pressure water inlet pipe (7) in the base (6), back-pressure water inlet pipe (7) one ends feed base (6) middle part and communicate with pressure chamber (10), the interior opposite side of base (6) is provided with a rhizosphere and compresses into a water pipe (9) and a soakaway trench (8), confined pressure water inlet pipe (9) one ends communicate with pressure chamber (10), soakaway trench (8) passes pressure chamber (10) and links to each other with gland (11), it is characterized in that:

A. soil cement sample (3) is installed on the base (6) in the pressure chamber, after soil cement sample sidewall is coated with thin layer vaseline or oily matter, in soil cement sample outside cover rubber membrane (4); Permeable stone (2) is all installed in soil cement sample upper and lower part, and the permeable cap in rubber membrane and base and top is tightened with bungee, makes the soil cement sample place sealed environment; After loam cake (1) and seal closure (5) are installed, gland (11) pushed down and fixing soil cement sample;

B. soakaway trench (8) is connected and surveys in the osmotic flow buret (8a), this pipe is connected atmospheric pressure;

C. give the σ 3 that exerts pressure of pressure chamber (10) around the sample by confined pressure forcing pump (9a) and confined pressure water inlet pipe (9);

D. apply opposite pressure σ b for soil cement sample bottom by back-pressure forcing pump (7a) and back-pressure water inlet pipe (7), make σ ₃＞σ _b

E. every interval certain hour Δ t surveys and reads osmotic flow buret water seepage amount, and when the osmotic flow buret had water evenly to ooze out, the expression sample was saturated, opening entry seepage flow, measuring water temperature T in process of the test simultaneously;

F. according to the darcy theorem, adopt theoretical calculation formula

Calculate the infiltration coefficient of sample, in the formula: k _TThe infiltration coefficient cm/s of soil cement sample when being T ℃ for water temperature; Δ V is seepage flow cm ³H is specimen height cm; A is the long-pending cm of sample cross ²r _wDensity g/cm for water ³σ _bOpposite pressure kPa for given sample; Δ t is Seepage flow time s.

Images