Abstract:In order to explore the plastic cumulative strain effect of red clay under long-term cyclic dynamic load, saturated remolded red clay in Nanchang area was used for cyclic triaxial test under uniaxial loading.The effects of dynamic stress ratio, initial porosity, consolidation confining pressure, loading frequency and drainage conditions on plastic cumulative strain and dynamic pore pressure of red clay were studied.The results of tests indicate that：with the increase of dynamic stress ratio, the deformation curve of red clay transits from gradual stable type to destructive type.When the dynamic stress ratio is less than the critical dynamic stress ratio, with the increase of cyclic vibration times, the plastic cumulative strain and dynamic pore pressure development curves of red clay both show initial rapid growth, and then the inflection points appear and finally tend to be stable.Under the same dynamic stress ratio, the cumulative strain and dynamic pore pressure of the sample increase with the increase of initial porosity and consolidation confining pressure, and decrease with the increase of loading frequency.At the same time, the cumulative strain under undrained condition is larger than that under drained condition.The larger the plastic cumulative strain is, the later the inflection point of strain development curve appears.With the increase of dynamic stress ratio, the softening degree of the soil increases, but at higher cyclic vibration times, the softening degree decreases.

Abstract:Unloading is a common condition that causes damage to geotechnical materials.In order to investigate the strength characteristics of the coarse-grained soil under three-dimensional unloading in different cases of the coefficient of intermediate principal stress b, several three-dimensional equal unloading tests in which the spherical stress p decreases with constant b and constant deviatoric stress q (300 kPa) were performed on coarse-grained soil by using true triaxial apparatus.The strength characteristics of coarse-grained soil were analyzed and the applicability of the commonly used strength criterions was studied.The test result shows that under the condition of three dimensional equal unloading, the strength parameter of coarse-grained soil is related to the coefficient of intermediate principal stress b.When b equals to 0, the internal friction angle φ_b is the minimum and the failure stress ratio M_b is the maximum.The stress ratio at failure decreases with the increase of b and, as b increases the gradient decreases gradually.The internal friction angle increases with b for small b values while decreases with the increase of b for large values.This can be explained by the co-impact of the shearing in three directions.All of the three strength criterions, including the Matsuoka-Nakai criterion, the criterion expressed by stress invariants of coarse-grained soil and Lade-Duncan criterion, can response the law between φ_b and b.It is found that the Matsuoka-Nakai criterion is the closest to the test results for small b values while the strength criterion expressed by stress invariants of coarse-grained soil is the closest to the test results for large b values.It is also found that the corner function strength criterion of coarse-grained soil is consistent with the experimental results.

Abstract:In recent years, the airport high coarse-granular fill construction in the southwest mountain area of China has entered a stage of rapid development, and coarse-grained soils such as rockfill materials with comparatively good engineering characteristics are widely used in high coarse-granular fill. The internal stress of high coarse-granular fill is large, and coarse-grained soil will cause particle breakage. It is of great engineering significance to analyze the impact of particle breakage characteristics on the deformation and stability of high coarse-granular fill. Modeling high coarse-granular fills using discrete element particle flow method. The deformation evolution process of the high coarse-granular fill is simulated through the strength reduction method. Based on the Russell & Muir Wood particle breakage criterion, two cases of particle breakage and don’t breakage were simulated and analyzed respectively. In addition, we also focus on the effect of particle fragmentation on the deformation and stability of the high coarse-granular fill. DEM modelling results indicate that the small-size grains abraded from the host coarse-granular grains will slip and fill the gaps among the host grains, leading to an increase in deformation and a decrease in the shear strength, and further resulting in a decrease in safety factor and stability of high coarse-granular fill.

Abstract:Soft soil foundations are prone to large deformation, long settling time and difficult to predict under long-term repeated loading.Aiming at this problem, the one-dimensional consolidation analytical solution of soft soil foundation under rectangular and trapezoidal repeated loads is solved by the one-dimensional consolidation theory of K.Terzaghi.The soft soil under repeated loading is proposed by ABAQUS finite element software.Numerical analysis and prediction method for long-term consolidation deformation of foundation.This method is combined with engineering examples to analyze the long-term development and change of soft soil foundation settlement, pore pressure, effective stress and void ratio under repeated loading with time.It is found that the settlement is proportional to the horizontal loading time of repeated load; pore water the final development trend of pressure is to fluctuate around 0; the effective stress increases with the total number of loading times; the change of void ratio is related to soil depth, loading size and loading times, the simulated values, theoretical values and measured data under different load types are compared and analyzed, and the settlement curve under the equivalent repeated load was found to be in good agreement with the actual measurement.

Abstract:This study performed a series of laboratory tests for understanding the role of heavy metal ions in the physical-mechanical behaviour.Different kinds of soils, including kaolinite, illite clays and sodium bentonite, were mixed with different concentrations of heavy metals Cu²⁺, Zn²⁺, Pb²⁺ to measure the changes in the Atterberg limits and the undrained shear strength.The testing results show that: the liquid limit and plasticity index of low active soils increase with the ion concentration, but sodium bentonite shows the opposite trend; the undrained shear strength of low-active soils increases with the ion concentration, but conversely for the high-active soils; based on the existing quantitative correlation between physical and mechanical properties of non-polluted soils, the quantitative relationship between the undrained shear strength and liquidity index of contaminated soils is investigated.It is found that the changes of undrained shear strength caused by adding heavy metal ions can be attributed to the corresponding changes in liquid limit and plastic limit.Such a result indicates that there is almost no chemical reaction caused by heavy metal pollution.The physical-mechanical quantitative relationship of heavy-metal-contaminated soils is consistent with the existing empirical relationship of non-polluted soils.

Abstract:In Shandong province, silt is widely distributed in the Yellow River flooding area.In the case of shortage of railway roadbed filling material, reinforced silt is commonly used as an alternative.In this study, the silt in the Yellow River floodplain area was reinforced by using nano-silica and lime as modifiers.The strength of the silt was measured by compaction test and unconfined compressive strength tests.It was found that although the strength of the silt was significantly improved, the material also showed some characteristics of brittleness.In order to overcome this disadvantage, polypropylene fibers were added to silt and then, the influences of fiber content and length on the strength and brittleness of the silt were studied through a series of experiments.The optimum fiber content and the optimum fiber content were determined.The results show that the brittleness and compressive and shear strength of the silt can be improved by adding fibers; and when the content of fibers is 0.4% and the length of fibers is 2 cm, the improvement effect is the best.

Abstract:In order to investigate the influence of strength reduction of loess induced by rainfall infiltration on the stability of tunnel, direct shear- and triaxial- tests were carried out on loess.The results show that the water content has significant influence on the mechanical behaviors of loess.The elastic-plastic incremental constitutive relation of undisturbed soil was established.By compared with experimental data, the constitutive model was proved to be capable of describing the stress-strain relationship of loess.The distribution characteristic of water content in different depth land under different rain intensity were analyzed.Besides, the constitutive model for loess with different water contents were established so as to calculate the stress and deformation of structure in tunnel under different rain intensities.The results show that when considering rainfall infiltration, the deformation of tunnel and the stress of preliminary support structure are significantly increased.In this situation, the settlement of the tunnel vault increases 46% and the stress of preliminary support structure increases 20%~27%.It is found the elastic-plastic incremental constitutive relation is reasonable and results of the numerical simulation is reliable with comparing the calculated and measured data of tunnel deformation.

Abstract:In order to study the effect of reinforcement of entire basal soil on the deformation and stress of foundation pit, the effect of the reinforcement of entire basal soil at the bottom of foundation pit on the ground surface settlement, the lateral displacement of top beam, the bending moment of pile and the earth pressure behind pile was studied by laboratory model test.The ABAQUS finite element software was used to simulate the model test and the experimental data were compared with the numerical results.The effects of cement-mixed ratio and reinforcement depth on the deformation of foundation pit were analyzed.The results show that the effect of reinforcement of entire basal soil is the most obvious to reduce the bottom heave, the lateral displacement of retaining structure is more obvious, and the ground surface settlement is not obvious.The range analysis method shows that increasing the elastic modulus of reinforced soil is more effective than increasing the reinforcement depth to restrain the lateral displacement of supporting pile and the soil heave of foundation pit.When the cement-mixed ratio exceeds a certain range, the reinforcement effect is not significantly improved.It is suggested that the cement-mixed ratio is generally 5%~20% in the soft soil area with 20% water content.When the soil reinforcement depth exceeds a certain range, the effect of controlling the deformation of foundation pit is improved but not obvious.It is suggested that the soil reinforcement depth should be 0.4~0.45 times the depth of foundation pit.

Abstract:In order to reduce the differential settlement between the new and old embankment, prevent the new embankment collapsing and the pavement destroying, pile-supported reinforced-earth wall is carried out to widen embankment on rheological soft-clay.The existing railway slope was cut to 1∶0.5 after opening to traffic at different times.Then filling subgrade and operating it three years.The software FLAC^3D was used to build a model to analyse how the operation time can affect the movement of retaining wall and the settlement of embankment and foundation after widening the subgrade.Discussing how the position of the pile and the way of widening will affect this subgrade widening structure.The experimental results demonstrate that the pile-supported reinforced-earth wall has great stability and bearing capacity.After widening, the existing roadbed appears reverse slope phenomenon obviously, but the slope ratio is less than 0.4% of the allowable road slope ratio of road functional requirements and structural requirements.Using pile-supported reinforced-earth wall can not only reduce the influence of widening subgrade on existing subgrade, but also reduce the settlement of the widening subgrade.

Abstract:The impact-echo method is an effective method for pile integrity testing.Based on the one dimensional (1-D) stress wave theory, the range and the extent of the changes in pile impedance can be determined from the vibration curve of reflected wave at the top of pile (including travel time, amplitude and phase).However, in practice, a pile is a cylinder rather than a rod for the induced waves, and the section deformation is not uniform.In this study, the three-dimensional wave phenomena exhibited in the wave-field near the pile top are analyzed from the components of the wave excited by the point sources and the multiple reflections from the side of the pile top.The propagation behavior of the waves in the far-field, which is far from the top, is analyzed based on the longitudinal waves in cylinders.The results show that the three-dimensional wave in the near field and the dispersive characteristics of the waves in the far field can be mitigated, and the signals measured at the top can be approximately analyzed using 1-D stress wave theory when the receiver position and source frequency content meet some conditions.Under the interaction between the pile and the soil, the stress waves in the pile decay with propagation.The effects of shear wave velocities of pile and soil on the attenuation of stress wave are analyzed.It is shown that the stress wave attenuation is not only related to the shear wave velocity ratio of the pile and soil, but also related to the absolute values of the shear wave velocity of the pile and soil.The lower the shear wave velocity of the pile is, the higher the shear wave velocity of the soil is, and the faster the stress waves decay.

Abstract:The development of the Chinese rail-road bridge has been nearly 80 years old, from the early beam system with small span and simple structural force to the current arch system with large span, as well as the cable-stayed and suspended cable system with large span and super large span.This paper collects relevant information of the rail-road bridge of the four structural systems that have been built and under construction in China, analyzing the main beam structure and foundation of the main bridge of the four kinds of structural systems in China, and the development trend of structural design, construction technology and material performance of different structural parts.Through analysis, the following conclusions are drawn: in terms of structure, the main raft form, bridge deck and joint system of the main girder of the four structural systems are from simple to simple, from discrete assembly to integral bolt welding;in terms of mechanical properties, the main truss and the main girder bridges of each structural system complement each other,this fully exerts the performance of the material and the stress characteristics of the structure,the main beam construction process tends to be systematic, efficient, and economical, and its material properties tend to be high quality; there is no significant change in the type of foundation, but its construction method has achieved self-innovation and the material performance tends to be high quality; the main arch of the arch-type system of the rail-road bridge tends to be new in design, and tends to be complicated in the construction process, and tends to be scientific and economical in the selection of materials;in addition to the main beam and the foundation part of the cable-stayed and suspension system, the design of other parts of the structure tends to be scientific, the construction tends to be economical and intelligent, and the material performance tends to be high quality.

Abstract:The coupling vibration of space vehicle-bridge of this kind of bridge was analyzed basing on a curved continuous box girder bridge on an ramp.The ANSYS software was used to simulate the beam bridge, and the typical three-axis space vehicle model was selected.The dynamic response and impact of the curved continuous box girder bridge under the braking effect of the vehicle were obtained by the MATLAB program of the highway curve using the modal comprehensive method.And the influence of initial speed, braking position, braking rising time and bridge deck smoothness on dynamic impact coefficient was studied.The results showed that the maximum deflection, deflection and internal force impact coefficient of the main girder do not increase or decrease monotonously with the increase of initial speed, but they are obviously larger than the results when the vehicle runs at the same initial speed and may exceed the standard value.The impact coefficient of deflection and mid-span shear force in front half-span braking is greater than that in the back half-span braking.At the same time, when the braking position of the vehicle is greater than half-span and closer to the fulcrum, the impact coefficient of deflection and internal force is closer to the result of uniform speed braking.With the increase of curvature radius, the impact coefficient of deflection, bending moment and torsion of bridge decreases gradually, while the impact coefficient of shear force increases gradually.In addition, the impact coefficients of deflection, bending moment and torsion curved bridges are larger than those of straight bridges and emergency braking tends to aggravate bridge vibration.

Abstract:To solve the problem of determining reasonable completion state and construction state in cable-stayed bridge design and monitoring calculation, a cable force optimization method based on MOPSO algorithm is proposed.This method adapts to multi-objective and multi-constraint cable force optimization by adding external reserve set and optimizing update strategy based on PSO algorithm.Compared with the single objective optimization method which has the limitation of single solution, MOPSO algorithm considers more comprehensive factors.The Pareto optimal solution set obtained by MOPSO algorithm can be further screened by decision makers based on experience.Python programming language and finite element software are used to compile the optimization program based on this method.The sum of the bending strain energy of the main tower and the main beam, and the sum of squares of longitudinal displacement under dead load is taken as the objective function after the completion of the bridge.The constraints are that the structure is in a safe state during the construction process and after the completion of the bridge and the overall distribution of cable forces is uniform.The optimization results of engineering examples show that the proposed method can quickly find the Pareto optimal solution set and select the optimal solution.The stress of the structure is in the safe range, the main tower is reasonable in alignment, and the overall distribution of cable forces is uniform.The method can be applied to determine the cable force in completion and construction of cable-stayed bridge and the suspender force of girder and arch combination bridge.

Abstract:Explosion overpressure is an important indicator to describe blast load.And the results obtained by different methods have high discreteness.Based on this, the reflection coefficient formula of the relationship between incident overpressure and reflection overpressure is determined firstly by analyzing the experimental data chart fitting.Then a large number of theoretical calculation formulas and explosion test data were collected and transformed to analyze the distribution characteristics of explosion overpressure at different proportional distances.The results show that the probability density of explosion overpressure obeys exponential distribution when the scaled distance less than 0.5 m/kg^1/3.And obeys normal distribution when the scaled distance greater than 0.5 m/kg^1/3.The variation coefficient reaches the maximum value 1 when the scaled distance less than 0.5 m/kg^1/3.While variation coefficient is in the range of 0.13 to 0.2 when the scaled distance within the range of 1.5 m/kg^1/3 to 6 m/kg^1/3.The variation coefficient of reflect overpressure is a little bigger than that of incident overpressure.According to the expected data of explosion overpressure distribution at different proportional distances, the calculation formula of explosion overpressure and the calculation formula of explosion overpressure distribution range with 95% guarantee rate are obtained by fitting.

Abstract:Aiming at the problem that low-rise buildings are easily damaged by typhoons, this paper presents a protection method by installing a new type of wind-resistant energy-dissipation devices on low-rise buildings.To find the optimal arrangement of proposed devices and maximizing the utility of the devices, six cases with different installing schemes were analyzed in this paper, including to install the device on the edge of the double-slope roof, the roof ridge, and installed with spoiler.The influence of energy-dissipation devices system on peak wind pressure and average wind pressure of roof were studied by wind tunnel experiments.The numerical simulations of the 6 installation cases were carried out, and the simulation results are consistent with the wind tunnel test.The optimization on the geometric parameters of energy-dissipation devices was studied, and the influences of the tip speed ratio, blade root angle and blade to tip torsion angle on the energy-dissipation coefficients were studied.The results show that the installation of energy-dissipation devices can effectively prevent the roof damage from wind.In addition, by combining the spoiler and the energy-dissipation devices at the windward side of the eave, the adverse effects of wind suction on the roof structure can be significantly reduced.The aforementioned installation method can significantly reduce the extreme value of the average wind pressure coefficient of the roof (in both windward and leeward sides) at any wind direction angle and the reduction ratio is up to 40%.

Abstract:In order to identify the damage of transmission tower and other engineering structures under the influence of uncertain factors, a cloud reasoning algorithm based on associated mode is presented.Firstly, residual force equation is established and damage identification principle based on residual force vector is analyzed.Then, a cloud reasoning algorithm based on residual force is proposed.Numerical characteristics of cloud model are given, front cloud generator and rear cloud generator are analyzed, qualitative rules based on gray cloud model are proposed, and corresponding cloud reasoning system is composed by using cloud rules.Finally, given the drawback that residual force is susceptible to uncertain factors such as measurement noise, a cloud reasoning algorithm based on associated mode is presented to enhance the identification accuracy and reliability.And a transmission tower structure is applied to damage identification.The simulation results indicate that the cloud reasoning algorithm based on associated mode can well identify structural damage, and the identification results of the proposed algorithm are obviously superior to those of residual force vector method and the cloud reasoning algorithm based on residual force.

Abstract:To provide the basis for the analysis and design of fire-resistance of bolt connections in steel building, the mechanical properties of the stainless steel bolt at elevated temperature were studied.Two groups of stainless steel bolts with different grades were tested to obtain the full stress-strain curve of stainless steel bolts at different temperatures.The Young’s modulus, 0.2% proof strength and tensile strength of stainless steel bolts were derived.The test results were compared with the mechanical properties of the parent materials and fire-resistant bolts at elevated temperatures, and the recommended values for parent materials in relevant design standards.Based on the experimental data, reduction factors models for tensile strength, Young's modulus and 0.2% proof strength are proposed in this paper for stainless steel bolts at elevated temperatures.The test results shows that the tensile strength degradation of stainless steel bolts at elevated temperatures are found to be rather close to those recommended by Eurocode 3 for their parent materials, but the reduction factors of Young's modulus are of great discrepancy.When temperatures lower than 650 ℃, the 0.2% proof strength of stainless steel bolts decreases more slowly than that of their parent materials.In the temperature range of 500 to 900 ℃, the stainless steel bolts retain their tensile strength, Young's modulus and 0.2% proof strength better than fire-resistant bolts.

Abstract:Through the fatigue test of 10 groups of drawing specimens with diameter of planting reinforcing bar of 16~25mm and embedment depth of 10d~25d (d is diameter of planting reinforcing bar ), effect of fatigue load on tensile strength and bond stress of anchor bars had been studied.The specimens were not damaged after 2 million times of fatigue loading with an upper limit of 0.45P_u, then applied static load to failure.Strain, slip and load of planted bars are measured during loading.Results demonstrate that the fatigue load weakens tensile strength, and the ultimate load decreases after fatigue loading.The decrease of bond stress has a logarithmic trend with the increase of cyclic loading times.The relationship of the bond stress and the failure form of the specimen is analyzed.It is found that the bond stress at the interface between rebar and chemical adhesive is the main factor to control whether the specimen failure or not when reaching certain embedment depth.Increasing the diameter and embedment depth of anchor bar, the peak of bond stress gradually decreases; the stress distribution curve along the embedment length tends to be gentle, which improves the overall stress performance of the anchor bar.

Abstract:In order to study the seismic performance of the prefabricated frame joints with high strength reinforcement and steel fiber concrete, two precast concrete joints and one cast-in-situ concrete joint were conducted under low cyclic reversed load test, the failure characteristic, hysteretic behavior and energy dissipation were analyzed.The results show that the prefabricated beam-column interior joints with high strength reinforcement and steel fiber concrete, which the H-steel was adopted in joint core area, present bending failure of beam end, which meets the seismic design principle of “strong column and weak beam”.The cast-in-situ concrete joint and the joint connected by the steel plate welded end plates occur shear failure in the joint core zone, while the failure mode of prefabricated joint significantly improves.The use of steel fiber in core area and assembly segment can reduce the crack width and propagation, lighten concrete protection spalling and improve the damage pattern of joints.The ultimate load, hysteretic performance and energy dissipation capacity in the prefabricated beam-column joints are improved, the stiffness degradation is retarded and the seismic performance of prefabricated joints are improved.

Abstract:The erosion behavior of reinforced concrete by chloride ions in ocean atmosphere can be divided into two phases.At first, chloride ions attach to the surface of concrete under the action of wind, and then erode from the surface into the concrete.Based on the whole process of chloride ions erode on concrete in marine atmosphere, this article has summarized existing research both at domestic and abroad.On the one hand, this essay expounds the various influencing factors on the influence of deposition process, The salinity of seawater, wind speed and exposure time were positively correlated with the amount of chloride ion deposition in concrete, while the distance from the coast was negatively correlated with the amount of chloride ion deposition in concrete.On the other hand, discussing the influence of transfer process from the various influencing factors.The influence law of various influencing factors on the transmission process is discussed.The higher the water-cement ratio is, the longer the exposure time is, the higher the temperature is, the larger the internal and external humidity gradient is, and the more serious the carbonization is, the easier to form the convection zone.At present, the researches which aim at the deposition and transport behavior of chloride ions in marine atmosphere are based on single factor.The deposition and transport behaviors under the coupling of multiple factors need to be further studied.

Abstract:Shotcrete permanent support structure of long highway tunnels in high-latitudes and high-altitudes area is subjected to the action of freeze-thaw damage and carbonation which degraded structure durability performance and increased the tunnel maintenance and operation cost.Carbonation durability of frost-damaged-shotcrete was investigated by using freeze-thaw cycles in air firstly and then accelerated carbonation method.With the evaluating indicator of carbonation depth and relative compressive strength, the deterioration law and influence factor of carbonation depth were researched.Results show that frost damage accelerated the carbonation rate and carbonation depth was deeper with the relative dynamic elasticity modulus decreased.The relative compressive strength of frost damage shotcrete increased with the increasing of carbonation depth.However, when frost damage degree was more than 10%, the influence of relative compressive strength on frost damage shotcrete was not obvious.Furthermore, the carbonation depth prediction model of shotcrete was established considering frost damage degree, shotcrete mixture parameters and concrete forming mode by using IBM SPSS statistical software to analyze the test data.The overall error between the predicted value and the experimental data was less than 20%, and the standard error was 0.16. This indicates that the model has good applicability.

Abstract:In recent years, advanced oxidation technology (SR-AOPs) based on sulfate radical (SO₄^·-) is developing rapidly.The catalysts and related mechanisms for the stable and efficient generation of SO₄^·- have been focused by researcher.In this work, the heterogeneous silicon-based highly dispersed cobalt oxide (CoNSi) was synthesized through ammonia modified adsorption roasting method.Moreover, CoNSi was used to activate the industrial by-product sulfite (S(IV)) to achieve the purpose of “waste control by waste”.The effect of pH value, CoNSi and sodium sulfite (Na₂SO₃) dosages, AO7 concentration, and oxygen on the degradation of AO7 was investigated separately.Furthermore, the effect of sulfite concentration and AO7 concentration on the initial rate of AO7 degradation reaction was analyzed.The results indicated that the degradation efficiency of AO7 in aerobic environment could reach 79.4% under the conditions of initial pH of 9.0, CoNSi of 0.25 g/L, Na₂SO₃ of 1.0 mM and AO7 of 7 mg/L.Moreover, the stability of CoNSi activated sulfites was demonstrated by sequencing experiments.Radical trapping experiments elucidated that SO₄^·- is the main active species in this system.

Abstract:In order to determine the degradation of mixed bacterial suspension of five petroleum hydrocarbon degrading bacteria extracted in the laboratory on gasoline-contaminated soil, we had made use of gas chromatography-mass spectrometry to implement qualitative analysis on gasoline-contaminated soil compounds degraded by degrading bacteria in order to assess whether such mixed bacterial suspension has the ability to degrade the gasoline-contaminated soil.Moreover, considering the factors of pH value, temperature, soil moisture content and inoculation amount of degrading bacteria, single factor test and multi-factor orthogonal test were adopted to determine the degradation rate with the purpose of optimizing the degradation conditions of gasoline-contaminated soil by the mixed bacterial suspension.Under the single factor test, the compound components before and after the test were compared, it was found that these five degrading bacteria extracted in the laboratory have good ability to degrade the gasoline-contaminated soil.And from the relative peak area ratio chart, it is discovered that temperature and inoculation of degrading bacteria have more significant effects on the degradation of degrading bacteria than moisture content and pH.When the pH is between 6 and 8, the degradation temperature between 30 ℃ and 35 ℃, the moisture content between 15% and 25% and the inoculation amount of degrading bacteria between 1 ml and 2.5 ml, the degradation effect of mixed bacterial suspension is relatively obvious.Under the condition of multi-factor orthogonal test, the optimum degradation conditions of mixed bacterial suspension are as follows: temperature is 32℃; pH value is 7; inoculation amount of degrading bacteria is 1 mL and water content is 25%.