182 results about "Maximum dry density" patented technology

The invention discloses a method for building a highway road bed with waste steel residues. The method comprises the steps: firstly, waste steel residues are adopted to build the road bed; secondly, the building speed of the road bed built with waste steel residues is required to be controlled to guarantee the road bed stability; thirdly, the road embankment built with waste steel residues is compacted by a vibratory road leveling machine in layers, during the compacting, the waste steel residues shall be in the optimum moisture content scope, through the trial road section method, the appropriate compacting machines and tools are determined, and the maximum dry density and the optimum moisture content are adopted as the compaction degree calculating standard in the road bed built with waste steel residues; and fourthly, the cross section design of the waste steel residue road embankment comprises the road embankment height, the side slope ratio of the road embankment, the building layer thickness, a top sealing layer, a bottom sealing layer, an intercalated layer, the slope protection and a drainage system. The invention has the advantages that the method is easy, the operation is convenient, the waste steel residue piling ground and the environmental pollution are reduced, the wastes are changed into valuables, the environmental protection is promoted, the method solves the problem that the highway engineering packing material is inadequate, the cost is low, and the quality of the built road bed can satisfy the construction requirements of the road bed of the higher grade highway.

The invention discloses a crack resistance type cement stabilized macadam proportioning design method based on vibration test method. The design method is implemented according to the following steps:(1) preparing framework dense graded aggregate; (2) adding cement into graded aggregate to obtain a cement stabilized macadam mixture, and adopting vibration compaction test method to determine the maximal dry density and the optimal water content of the cement stabilized macadam mixture, wherein the added cement dosage accounts for 3-5% of the graded aggregate according to mass percent; (3) adopting the cement stabilized macadam mixture in step (2) and vibration compaction test method to prepare a cement stabilized macadam cylinder test piece with the dimension being 15cm in diameter * 15cmin height; (4) carrying out an unconfined compression strength test on the cement stabilized macadam cylinder test piece which is subject to 6 days of preserving and 1 day of water soaking, and designing the cement dosage according to the result of the unconfined compression strength test. The cement stabilized macadam designed by the invention can better form a compact framework structure, featuring unlikely dissociation, the maximal dry density, the optimal water content and saving of 30-40% cement use amount, has the advantages of high strength, good crack resistance and good scour resistance, and basically solves the problems of serious crack of cement stabilized macadam which perplexes road engineering circles, at home and abroad, all the time.

The invention discloses a method for preparing a road (bottom) base material cylindrical test piece simulating on-site rolling effect. The vibration compaction test method is adopted to determine the maximum dry density rhodmax and the optimal moisture content wo and the vibration method is adopted to prepare the cylindrical test piece. The operation process of the method corresponds to the on-site practical construction process. The maximum dry density and the optimal moisture content of the tested (bottom) base material and the prepared test piece coincide with the on-site practical rolling effect. The test result of the performance of the test piece is objective and real; and the method has good repeatability. Steps of measuring the moisture content of dried aggregates and moisture content of dried test samples, a step of interlayer broom-finish treatment, a step of flattening the surface of the samples and the like are saved; the material feeding process is simplified; and the working efficiency is improved. The method has the advantages of simple operation, reliable result and good repeatability.

The invention relates to a vibration-molding-based cement stabilized macadam mixing ratio design method, which comprises the following steps: (1) preparing optimized dense skeleton type graded aggregate; (2) adding cement into the graded aggregate to prepare cement stabilized macadam mixture; (3) vibrating and compacting the cement stabilized macadam mixture, and determining the optimal water content and the maximum dry density of the cement stabilized macadam mixture in mode of a vibration and compaction test; (4), preparing cement stabilized macadam cylindrical test pieces by using a vibration molding test process at a compactness of 98 percent under the determined maximum dry density and the optimal water content; and (5) perform an unconfined compression test on the prepared cement stabilized macadam cylindrical test pieces and determining the dose of the cement according to the result of the unconfined compression test. The cement stabilized macadam mixture designed by the invention has the characteristics of high strength, high crack resistance, convenience for construction and low cost, and an innovation is made in semi-rigid material design on the basis of a material design guiding ideology.

The invention discloses an experimental method for measuring maximum dry density of a road base material, which comprises the following steps: filling a mixture into a test die, fixing the test die on a vibration gauge, and vibrating and compacting the test die for 100 to 120 seconds; calculating the dry density of the sample, repeating the experiment for five times to obtain five groups of blended water contents and dry densities of the sample, and drawing a relation curve of the water contents and the dry densities, wherein the horizontal coordinate is the blended water content, the longitudinal coordinate is the dry density, the dry density corresponding to a peak value of the curve is the maximum dry density and the corresponding water content is the optimal water content; and parameters of the vibration gauge are configured as follows: 30+/-2Hz of vibration frequency, 7.6+/-0.2kN of exciting force, 1.4+/-0.2mm of nominal amplitude, 3.0+/-0.4kN of working weight, 1.2+/-0.2kN of loading system, and 1.8+/-0.2kN of unloading system. The method has the advantages of simple and convenient operation, reliable result and good repeatability.

The invention relates to a vibration molding-based method for design of mix proportion of graded broken stones, comprising the following steps: (1) selecting raw materials: selecting limestone as the base stone of the graded broken stones, adopting a reaction crusher to roll till the technical requirements are met; and selecting drinking water as added water for the mixture of the graded broken stones; (2) preparing optimized graded broken stones; (3) adding the drinking water into the graded broken stones in the step (2) according to 4-5% of water content to prepare a plurality of groups of mixtures of the graded broken stones; (4) carrying out vibrating compaction on the groups of mixtures of the graded broken stones obtained in the step (3), and determining the optimum water content and maximum dry density of the mixture of the graded broken stones under a vibrating compaction test mode; and (5) verifying the performances: under the conditions of the optimum water content and the maximum dry density determined by the step (4) and 98% of compaction degree, adopting a vibration molding test method to determine the California bearing ratio (CBR) of a test piece. The mixtures of the graded broken stones designed by adopting the method have the characteristics that the strength is high, the total quality is high, the construction is simple and convenient and the cost is low.

The invention an application of applying the industrial alkaline residue to dealing the road subgrade and basal layer, the method includes the following steps: materials preparation; sun-curing and disintegrating the alkaline residue and the on-site soil; determining the best moisture capacity and the maximum dry density of mixture; mixing the layers of the soil according the predetermined ratio uniform and spraying water to reaching the optimum water content; paving and rolling on the spot, the compression of subgrade shallow layer is controlled above 97% and the compression of sub-subbase course and the subbase course are controlled more than 98%; after every layers are rolled, lying a layer of mixture after watering seven days and reaching the design strength requirements. The method applies the alkaline residue to road engineering, because it makes use of industrial residue comprehensively, it reduces the land occupied by alkaline residue, eliminates the environmental pollution cause by alkaline residue, meanwhile the alkaline residue replaces a lot of roadbed and packing materials, so it reduces the construction costs of municipal works and roads and reduces the territorial resources pressure caused by digging out cultivated land.

The invention provides a recycling method for shield tunneling residual soil and relates to the technical field of subway shield tunneling residual soil. The method comprises the following steps: 1, the residual soil produced by shield tunneling is subjected to innocent treatment, and mud and gravel particles are separated through stage-by-stage screening; 2, the separated mud is subjected to chemical component analysis, and the optimal water content and the maximum dry density of a soil sample are obtained by laboratory tests; 3, a proper soil stabilizer is selected according to different water content and different soil sample components for a mix ratio test; 4, the mud is cured for backfill of a foundation pit. After curing, 7d unconfined compressive strength of backfill can reach 1.5 MPa, strength requirements are met completely, the shield tunneling residual soil resources are used, and stacking of the shield tunneling residual soil is reduced.

The invention discloses a construction method of a multielement stiffness composite pile. The construction method comprises the steps that a plurality of spraying pipes for different materials are arranged in a stirring shaft, and nozzles of the spraying pipes are arranged at the different portions of the stirring shaft or stirring blades; when the stirring shaft runs in a hole, through high-pressure air sprayed by the spraying pipes, water cuts original soil, stirring is carried out, and therefore soil is softened; and the materials are sprayed into the softened soil and are stirred, meanwhile, through a chain and back pressure spiral blades arranged on a pile machine, cement composite soil within the total-length range is subject to rotary pressing, extrusion and expansion, and the high-strength multielement stiffness cement composite pile with the maximum dry density is formed. The multielement stiffness composite pile is reasonable in structure, convenient to construct and good in construction quality, and compression resistance, pulling resistance and horizontal force resistance are superior to those of existing pile types like a drilling pouring pile; according to the water content of different kinds of soil, the water containing ratio, the kind of curing agents and the mixing amount are adjusted; and according to the load character and magnitude, the type of the multielement stiffness composite pile can be adjusted, and therefore the strength of the multielement stiffness composite pile is coordinately matched with the strength of a core pile body.

The invention relates to a method and a tester for determining a relative density sample preparation standard of a laboratory scale test on coarse aggregate, and belongs to the technical field of geotechnical testing. The method comprises the following steps: firstly, selecting graded coarse aggregate, and conducting a heavy vibrating roller extremum dry density test to obtain maximum dry density values of a field test; through a surface vibrator compaction manner, adjusting compaction parameters of the tester to obtain the maximum dry density values under different compaction manners and compaction parameters; then, determining selected equivalent compaction parameters under an indoor compaction manner to serve as a compaction standard of a laboratory maximum dry density test; finally, performing a laboratory relative density test on a scale material according to the compaction standard to obtain the extremum dry density of the scale material; according to a design index, to determining the sample preparation dry density or porosity of the laboratory scale test on the coarse aggregate through calculation. According to the method and the tester disclosed by the invention, by aiming at the scale problem of the original graded coarse aggregate, the influence of the scale effect of the coarse aggregate can be reduced, and the precision of the laboratory test on the coarse aggregate is effectively improved.

The invention relates to a filling method of blown sand expansion polystyrene particle mixed light road embankment filling, which is a novel road embankment filling technology, and is an effective method for lightening road embankment load, and is a novel technique for saving earth which is used in construction of high speed road and reducing soft earth ground foundation process, and is a breakthrough of green circulating economic construction and development technique. The main procedures of the technology comprise measuring grain composition curve of blown sand particles, defining two parameters of blow sand EPS mixed light filling with different proportions, namely, the largest dry density and the optimum water content, defining unconfined compressive strength of blow sand EPS mixed light filling with different proportions, allocating and stirring blow sand EPS mixed light filling on site, blow sand EPS mixed light road embankment construction, blow sand EPS mixed light road embankment filling technology, blow sand EPS mixed light road embankment grinding technology, and blow sand EPS mixed light road embankment maintaining.

The invention discloses a survey humidification compaction test method for determining swelling soil embankment filling and compaction parameters, which specifically comprises the following steps of: 1) drilling holes for a survey to obtain the single-hole natural optimum water content of swelling soil; 2) calculating to obtain natural optimum water content; 3) obtaining maximum dry density through a standard heavy-duty compaction test method; 4) judging the nature of filler for road use; and 5) taking the optimum natural water content plus or minus 2 percent as compaction control water content for medium and weak swelling soil filler embankment filling compaction, and using the maximum dry density determined in the step 3 to calculate degree of compaction as a basis for compaction control dry density. By adopting a geological assimilating method, the natural water content corresponding to a soil body with maximum dry density in a natural swelling soil slope is taken as the optimum water content for swelling soil embankment filling compaction. Moreover, a corresponding natural soil body is used for conducting a standard compaction test and the dry density obtained through the compaction test is taken as the maximum dry density for swelling soil embankment filling compaction.

The invention relates to a testing method for the fine-grained soil compaction degree. The testing method comprises the following steps that a target backfill soil sample is selected, the selected soil sample is manufactured into five to nine sets of soil samples different in water content, the indoor moisture-density test is conducted, and the different water contents, the corresponding dry density value and the maximum dry density value are obtained; the penetration resistance values of the soil sample under different water contents and different blow counts in the first step are tested; the regression analysis is conducted on the recorded water contents, dry density value and penetration resistance values, and a regression relational expression is obtained; one test face is selected in the filling site, the quick penetration test is conducted 5-9 times, and the penetration resistance value every time is recorded; digging is conducted to the bottom of the test face in the fourth step, and the water content of the dug-out soil is tested; the relational expression in the third step is selected according to the water content value detected in the fifth step; and the average value of the penetration resistance recorded in the fourth step is calculated and then substituted into the relational expression selected in the sixth step, the dry density is calculated, and accordingly the compaction degree of fine-grained soil in the filling site is calculated.

The invention discloses a test method for measuring maximum dry density of soil and stone mixture of a road subgrade. The test method comprises the following steps of loading samples into a test die by two times, fixing onto a vibration compaction test instrument, and performing vibration compaction for two times, wherein the vibration compaction time is 50s each time, the parameter setting of the compaction test instrument is as follows: the vibration frequency is 25Hz, the excitation vibration force is 5.5kN, the nominal vibration amplitude is 1.4mm, the loading mass is 110+/-2kg, the unloading mass is 170+/-2kg, the eccentric block included angle is 0 degree, and the pressure of the static surface is 109kPa; testing the water content of each sample, and calculating the dry density of each sample; repeating the compaction test for five times, and drawing the dry density-water content relationship curve, wherein the transverse coordinate is the water content, and the longitudinal coordinate is the dry density; the dry density corresponding to the curve peak is the maximum dry density roudmax, and the corresponding water content is optimum water content omega0. The test method has the advantages that the operation is simple and convenient, the results are reliable, the variance is small, and the destroy to the raw materials is small.

The invention discloses a tailing sand two-component soil pavement sub-base layer mixture and a preparation method thereof, which are used for solving the problem of resource utilization of waste tailing sand. Iron ore dressing tailing sand and clay are used as main raw materials, are cured by lime and then are directly used for road sub-base layer filling. A sub-base layer material comprises the following components in percentage by weight: 15-40 percent of iron ore dressing tailing sand, 5-10 percent of lime and 50-80 percent of clay, wherein the sum of all the components is 100 percent. According to optimum water content and maximum dry density of the mixture, a pavement sub-base layer can be obtained through implementation of the conventional lime industrial waste residue stable sub-base layer construction process. According to the mixture and the preparation method thereof, the iron dressing ore tailing sand is applied to a road sub-base layer; a large amount of tailing sand is comprehensively utilized; the land occupied by a tailing pond is reduced; meanwhile, a large amount of sub-base layer filler is substituted; land resource is saved; and the road engineering manufacturing cost is reduced. In addition, the tailing sand-lime-clay mixture is prepared by applying a simple process and is convenient to promote and apply.

A method for comprehensive stabilization of iron tailings gravel base course through cement and soil stabilizer belongs to the technical field of fixing construction roads in E part of IPC of international patent classification. The method is characterized in that according to the laboratory test, the proportion of mixture is determined as follows: the ratio of cement, iron tailings, gravel and curing agent is equal to 4:48:48:0.02, the optimum moisture content wopt is equal to 8.5%, the maximum dry density rho max is equal to 2.181g/cm<3>, and curing agent practically adopted in a construction site is increased by 0.001%; when in construction by adopting mix-in-place, the cement amount is increased by 1%; when in construction by adopting centralized plantmix, the cement amount is increased by 0.5%; when in construction, the curing agent needs to be diluted by 100 times, and the curing agent needs to be shook well so as to dissolve the precipitate completely before use. During maintenance, the relative humidity is kept between 95% and 98%, and the maintenance time is 7-10 days. The method has the beneficial effect of providing a practical base course method, gravel is replaced by iron tailings sand, so that problems of environment pollution caused by iron tailings sand and shortage of gravel are solved.

The invention discloses a method for testing a maximum dry density of super grain size rough granule soil. The method comprises the following steps of: grouping granule grain sizes of a test sample at first; calculating representative grain sizes of a super grain size granule group and a non-super grain size granule group according to a mass weighing averaging method; determining a ratio of a volume of a gap between the super grain size granule and the non-super grain size granule to a volume of a super grain size granule entity, namely a super grain size granule porosity ratio, according to an established planar analysis model stacked by spheres having two grain sizes and an introduced space correction coefficient; according to a gross volume density of the super grain size granule, the mass percentage of the super grain size granule and the maximum dry density of the test sample free of the super grain size granule, the maximum dry density of the super grain size rough granule soil can be obtained. The method is definite in theory and easy in operation; the tested maximum dry density is more accurate; and more reliable data basis can be provided for engineering construction.

The invention discloses a construction method for lowering the construction compactness requirement of a high-liquid-limit soil subgrade construction by doping sand. The method comprises the following steps of: A, doping sand in high-liquid-limit soil in a subgrade; evenly stirring by using a rotary tiller, wherein the sand-doping amount is 15-25 percent; B, covering; and C, rolling by adopting a road roller, wherein the first static rolling speed is 1.5-1.7km/h, and the later rolling speed is 2.0-2.5km/h. Compared with raw soil, sand-doped modified soil which is adopted in the invention scheme increases the maximum dry density and decreases the optimal water ratio; due to the existence of rough particles in the rolling process, water and air in the soil can be smoothly discharged so as to reach the requirement for higher subgrade strength; after sand is doped, the strength and the stability of the soil body are enhanced, and the shrinking stress of the soil is lessened to prevent the subgrade from cracking. The scheme of the invention greatly decreases the construction cost without causing dust-rising phenomenon or environmental pollution in the construction process.

The invention provides a calculating method for a heat conductivity coefficient of soil mass minerals. The method comprises steps as follows: measuring relative density of soil mass and calculating the maximum dry density rho(d-max) of the soil mass; making saturated soil samples with dry densities being rhod1 and rhod2 respectively and measuring heat conductivity coefficients of the saturated soil samples; calculating volume Vs of the soil mass minerals in the saturated soil samples and volume Vw of water in the soil mass minerals; calculating heat conductivity coefficients of the soil mass minerals in the saturated soil samples with dry densities being rhod1 and rhod2 respectively; calculating the heat conductivity coefficient ks of the soil mass minerals. The calculating method has the effects as follows: the method has the characteristics of being direct, realizing convenient calculation and the like, and a means is provided for calculation of the heat conductivity coefficient of the soil mass minerals. On the basis of contrastive analysis for the relative error, the forecast error of the calculating method is within 4.46%. By means of improvement of precision, calculation precision of the heat conductivity coefficient of the soil mass minerals can be improved to the greatest extent, and convenience is brought to establishment of a forecasting method of the heat conductivity coefficient of the soil mass.

The invention discloses a sand-filling roadbed construction method. The sand-filling roadbed construction method comprises the following steps of measuring and laying off, original surface cleaning and road camber forming, excavating horizontal and vertical drainage blind drains, laying drainage blind drain anti-seepage geotechnical cloth, backfilling graded broken stone processing, paving seepagegeotechnical cloth, fine sand layering filling and compaction, surrounding soil filling and compaction, and roadbed prepressing and settlement observation. In the sand-filling roadbed construction, fine sands used as a roadbed filler is river sands with fine grained sands, silt content of the fine sands is no larger than 5%, optimum water content of heavy compaction standard is 9%-12%, and maximum dry density is 1.53g/cm<3>-1.58g/cm<3>. The problems of resource shortage and high cost of express way roadbed construction in an existing the area with shortage land resources are solved. The invention belongs to the technical field of the roadbed construction.

The invention provides a mix proportion design method for a constant-temperature modified asphalt mixture. The method comprises the following two steps: determining the mineral aggregate gradation and the optimal asphalt-aggregate ratio of the mixture, wherein the method is characterized in that the mineral aggregate gradation adopts multi-gravel gap gradation constructed by a power function; and forming a test piece by adopting a rotation compacting method and determining the optimal asphalt-aggregate ratio according to the asphalt-aggregate ratio corresponding to the tightest state and the maximum dry density of minerals under the condition of different asphalt-aggregate ratios. By adopting the method provided by the invention, the mix proportion design method for the constant-temperature modified asphalt mixture can be normalized, so that the quality of the constant-temperature modified asphalt mixture can be guaranteed.

The invention discloses a cement stabilized macadam mixture processing method and belongs to the field of road engineering. The cement stabilized macadam mixture processing method comprises the stepsof 1, determining the maximum dry density, the optimum water content, the cement consumption and the use quantity of coarse aggregates and fine aggregates through design of the mix proportion of cement stabilized macadam; 2, preparing cement slurry according to the designed optimum water content and the designed cement consumption; 3, stirring and mixing the cement slurry and the coarse aggregates; and 4, adding the fine aggregates to the mixed slurry obtained in the step 3 to be mixed evenly and then obtaining the cement stabilized macadam mixture. The cement stabilized macadam prepared through the method has the characteristics of being high in strength and crack resistance, durable, economical and friendly to environment and has great application and popularization value.

The invention discloses a structurally integrated cement stabilized gravel base layer or subbase layer design method. The method includes steps: working out a pavement structure combination; establishing a calculation model, and determining an age and modulus of each structural layer in the model; calculating a bottom layer tensile stress of a cement stabilized gravel base layer or subbase layer; determining a 7d compressive strength design standard [Rc7] and a 7d splitting strength design standard [Rs7]; designing mineral aggregate gradation; determining a maximum dry density Rhomax and an optimum water content wo of a cement stabilized gravel mixture material; testing a 7d unconfined compressive strength Rc7 and a 7d splitting strength Rs7, and determining a cement addition quantity which meets requirements that Rc7 is larger than or equal to [Rc7] and Rs7 is larger than or equal to [Rs7], so that designing is completed. The method has advantages of low input cost, simplicity and convenience in use and operation, great utilization effects and effectiveness in solving of problems of disjunction with pavement structures and proneness to shrinkage cracking of existing cement stabilized gravel design.

The invention discloses a cement stable regeneration aggregate gravel proportioning design method, which comprises the following steps of (1) determining the mineral aggregate grading range; (2) setting a plurality of cement and water consumptions; respectively preparing cement regeneration aggregate gravel mixed materials; (3) shaping the cement stable regeneration aggregate gravel mixed materials obtained in the step (2) by a rotating compression method; using the accumulated height change being smaller than 1mm after the continuous 10 times of compression as a stopping standard; obtaining a relevant curve between the mixed material water content and the density; analyzing the curve to obtain the optimum water content and the maximum dry density of the mixed materials; (4) manufacturing a sample in the optimum water content and maximum dry density state; performing 7-day no-lateral-restraint pressure resistant intensity tests on a test specimen; determining the proportioning ratio of the cement stable regeneration aggregate gravel. The method has the advantages that the stress state of the material during the semi-rigid base layer construction can be better simulated; the design result can be used for better guiding the field construction.

The invention provides a loess engineering property modification method and belongs to the technical field of soil modification on the basis of adding modified materials into soil. The method comprises the following steps: (1), airing loess and cement flue dust raw materials and sieving with a 2mm sieve; (2) uniformly mixing the sieved loess and cement flue dust at a dry mass ratio of 91:9; (3) carrying out a standard compaction test on a mixture obtained in the step (2), thereby obtaining a mixture with the optimal water content ratio and maximum dry density; (4), mixing the mixture obtained in the step (2) and water at an optimal water content ratio, compacting to obtain a mixed soil sample with the dry density value as maximum dry density after mixing uniformly, and curing the mixed soil sample for 28 days, thereby finishing loess modification treatment. The method has the advantages of treating loess by use of industrial waste cement flue dust, lowering the cost, saving resources, protecting the environment, improving the loess strength and lowering the water sensitivity.

The invention discloses a roadbed gravel soil dynamic resilience modulus estimation method which comprises the following steps: respectively configuring roadbed gravel soil with different stone contents, carrying out a compaction test on the roadbed gravel soil, and determining the optimal water content and the maximum dry density of the roadbed gravel soil with different stone contents; preparingtriaxial roadbed gravel soil samples with different compaction degrees by adopting the configured roadbed gravel soil with different stone contents, and carrying out dynamic triaxial test on the triaxial roadbed gravel soil samples to obtain dynamic resilience modulus values of the roadbed gravel soil samples under different working conditions; comparing and analyzing the dynamic resilience modulus values of the roadbed gravel soil sample under different working conditions, and establishing a roadbed gravel soil dynamic resilience modulus estimation model; fitting the roadbed gravelly soil dynamic resilience modulus estimation model to obtain model parameters, and finally estimating the roadbed gravelly soil dynamic resilience modulus under different working conditions by adopting the roadbed gravelly soil dynamic resilience modulus estimation model with the known model parameters. The problem that the dynamic resilience modulus of the roadbed gravel soil cannot be accurately estimated is solved.

The invention discloses a method for improving expansive soil by mixing nano-silica and ordinary cement, and belongs to the technical field of geotechnical engineering. A dry mass ratio of the nano-silica to the cement is 1:4, and the average particle size of the nano-silica is 25-35 nm. The expansive soil is medium expansive soil, and is evenly mixed with the nano-silica and cement in an optimumwater content state, and the obtained mixture is mechanically compacted according to the standard compaction work in order to achieve a maximum dry density corresponding to the optimum water content;and the mixture is cured for 28 d or more. The method can significantly improve the strength of the modified expansive soil and reduce the use amount of cement, has the advantages of environmental protection, energy saving and emission reduction, and has wide uses in the treatment of expansive soil-related geotechnical engineering disasters.

The invention relates to the technical field of sand and gravel material soil tests, and discloses a method for determining the maximum dry density of natural-gradation sand and gravel materials for damming. The method comprises the following steps: preparing density barrels according to the size of the sand and gravel material, digging a groove in a test site, laying fine sand on the bottom surface of the groove, and performing static rolling, leveling and compaction; arranging the density barrels at intervals in an extension direction of the groove, and marking positions of center points of the density barrels; manually mixing raw materials according to test required gradation, sequentially filling the density barrels and the groove around the density barrels with the raw materials, performing forward and backward driving vibration rolling for 26 times, performing precise calculation to determine residual rolling times, performing driving vibration rolling again, performing barrel top leveling after rolling completion, measuring the volume of each density barrel, weighing the mass of the sand and gravel materials in each density barrel, and then performing calculation to obtain the maximum dry density of the sand and gravel materials. The method adopts a more reasonable rolling manner, and can rapidly and accurately determine the maximum dry density of the sand and gravel materials, thereby avoiding damage to relevant equipment.